Risk Factors of Low Back Pain Among Filipino Male

Air-conditioned Bus Drivers

A Research Presented to The Special Studies Committee

of the College of Public Health

University of the Philippines, Manila

In Partial Fulfillment of the Requirements In PH 199

Submitted by Group 8 Gail M. Culla

Felicidad Clare S. Martinez Jay Patrick R. Santiago

Mia Marie M. Tad-y

Adviser Benjamin C. Vitasa, MD, MPH, PhD

23 February 2004

Abstract

The general objective of the study is to determine the risk factors associated with low back pain among Filipino male air-conditioned bus drivers. It specifically aims to describe the distribution of bus drivers according to age, long driving time, vibration exposure, long distance driving, duration of employment, driving posture, seat/workplace design and psychological factors; describe the distribution of bus drivers with low back pain by age, long driving time, vibration exposure, long distance driving, driving posture, seat/workplace design, and psychological factors; and determine the association of different risk factors with low back pain adjusting for the effects of confounders and other independent variables. An analytical cross-sectional design was used. Three hundred seventy-eight drivers of air-conditioned buses from eight bus companies located in an urban cluster of bus stations were included as subjects. A self-administered questionnaire was given to each subject to obtain data on independent variables such as demography, long distance driving, driving posture, seat design, vibration exposure, duration of employment as a bus driver, psychological factors and long driving time. Anthropometric data were gathered using a tape measure. The outcome variable, low back pain was assessed based on questions asked in the questionnaire, using as inclusion criteria, chronicity of at least 6 months, recurring at least twice a week and 30 minutes duration per experience of pain. Using logistic regression, the association of risk factors with low back pain was determined. The identified risk factors included age, insufficient work space, abnormal vibration, uncomfortable sitting posture, constrained posture, rough roads, boredom, depression, frequent movement of back, frequent movement of shoulders, long distance driving, long driving time, vibration exposure, employee satisfaction with management and height.

Results showed that constrained posture, long distance driving and employee satisfaction with management were significantly associated with low back pain. Drivers with any one of these characteristics have greater odds of having low back pain of 3, 2.2 and 2, respectively.

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1.0 Introduction

Transportation through a vehicle allows movement from an origin to its

destination. Through driving, the course of a vehicle is controlled. For commuters,

traveling by land would not be possible without the vehicle and the driver himself.

Drivers are people who consider driving as their profession and source of income. It

is of great importance for them to know that aside from the benefits they can get

from this job, their life can still be at risk. Aside from possible accidents due to work,

their health can also be at risk. Low back pain is a form of occupation-related

disease which may cause increased cases of absenteeism and lesser productivity

for the working population. Drivers, as part of this population, should be aware that

this health issue is not a minor problem and should be taken seriously because it

can affect them directly and even their employers.

All over the world, several studies on low back pain have been conducted but

only few have established its association with driving a bus. No known Philippine

study on low back pain among bus drivers exists. Bus driving is only one of many

jobs that persons with a driver’s license can go into. Having little knowledge on the

possible occurrence of low back pain due to driving and its prevention can adversely

affect the health and productivity of bus drivers. For these reasons, a study to

establish the association between long driving time and low back pain is important

and timely. Recommendations on the prevention of low back pain can be formulated

based on the study.

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2.0 Review of Related Literature

Low back pain (LBP) is chronic pain localized in the lumbo-sacral spine with

acute and sudden onset lasting for about thirty minutes and is intermittent and

recurring for at least twice a week for six months. It is the most common cause of

occupational disability in the industrialized societies and together with headache, is

the most frequent variety of pain which workers have to contend with. However,

physicians diagnose low back pain as acute if it lasts less than a month and is not

caused by serious medical conditions. Most cases clear up in a few days without

medical attention although recurrence after a first attack is common (1).

2.1. Epidemiology of Low Back Pain

Between 60% and 90% of the general population experience back pain at one

time or another during their lifetimes. In a study done in Denmark, it was noted that

40% of the general population had recurrent LBP in 5 years (2). A cross-sectional

study done in Nigeria among office workers revealed that 38% suffer from episodes

of LBP in a 12-month period (3). Another cross-sectional study showed that 60% of

women in a textile factory in Vietnam suffer the same condition (4). Greater in

magnitude is the 73%-76% prevalence of LBP among nurses in Switzerland shown

in an eight-year cohort study (5). Every year, nearly 15% of American adults visit

their doctors because of low back pain episodes (6). These data were gathered

through questionnaires, observations, interviews and health records.

Men and women are equally at risk. Low back pain is second to upper

respiratory infection as the reason for seeing a doctor. In the US, its cost is second

to cancer and heart disease. The Center for Disease Control reported that in 1995,

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over 20 million visits to physicians and clinics were related to back symptoms. Low

back pain occurred in 25% of the working population and the economic impact in the

United States has been estimated to be over $75 billion per year (6). According to

the National Research Council and the Institute of Medicine of the National

Academies, it affects about 1 million workers and costs the nation between $45

billion and $54 billion in compensation expenditures, lost wages and decreased

productivity annually (7).

The majority of patients with low back pain state that they have increased

pain while sitting or upon arising from sitting. It is believed that almost all LBP is

aggravated and perpetuated by poor sitting posture in both sedentary and manual

workers.

2.2. Low Back Pain and Driving

Several studies have shown the statistically significant relationship between

LBP and driving. In a cross-sectional study done in Denmark, the prevalence of

frequent low back pain among urban bus drivers was 57% (2). This figure is not far

from the 56.62% LBP prevalence seen among bus drivers in Lithuania (8).

However, the figure is slightly lower in a study done among Japanese truck drivers.

From 153 respondents, the prevalence of LBP in one month was 50.3% (9).

2.3. Anatomy and Pathophysiology of Low Back Pain

The important functions that the lower back or lumbar area serves for the

human body include structural support, movement and protection of certain body

tissues. It holds most of the body’s weight and is involved in bending, extending or

rotating at the waist. The lumbar spine and muscles protect the soft tissues of the

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nervous system and spinal cord as well as adjacent organs of the pelvis and

abdomen (10).

The lumbar spine is composed of vertebrae “stacked” together that forms a

movable support structure and protects the spinal cord from injury. Each vertebra

possesses a spinous process, a bony prominence behind the spinal cord, which

shields the cord's nervous tissue. There is also a strong bony "body" in front of the

spinal cord to provide a platform suitable for weight-bearing. The lumbar vertebrae

stack immediately atop the sacrum bone in between the buttocks. On each side, the

sacrum meets the iliac bone of the pelvis to form the sacroiliac joint of the buttocks

(10).

The discs are pads that serve as "cushions" between each vertebral body

which minimize the impact on the spinal column. Each disc is designed like a jelly

doughnut with a central softer component, the nucleus pulposus, which is capable of

rupturing or herniating through the surrounding outer ring, the annulus fibrosus, and,

thereby, irritating adjacent nervous tissue (10).

Ligaments are strong fibrous soft tissues that firmly attach bone to bone.

Ligaments attach each of the vertebrae and surround each of the discs (10).

The nerves that provide sensation and stimulate the muscles of the low back

as well as the lower extremities (the thighs, legs, feet, and toes) exit the spinal

column through bony portals called "foramen" (10).

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Many muscle groups which are responsible for flexing, extending, and

rotating the waist, as well as moving the lower extremities attach to the lumbar spine

through tendon insertions (10).

The aorta and blood vessels that transport blood to and from the lower

extremities pass in front of the lumbar spine into the abdomen and pelvis.

Surrounding these blood vessels are lymph glands and involuntary nervous system

tissues which are important in maintaining bladder and bowel control (10).

The uterus and ovaries are important pelvic structures in front of the lumbar

area of women. The prostate gland is a significant pelvic structure in men. The

kidneys are on either side of the back of the lower abdomen in front of the lumbar

spine (10).

The skin over the lumbar area is supplied by nerves that come from the roots

of the lumbar spine (10).

A back strain usually occurs when the muscles surrounding the spine are

forced to stretch too far, lift too much weight or move in such a way that they sustain

very small tears. A microscopic amount of bleeding into the muscle usually results

from the tearing of the muscles and ligaments, followed by swelling and muscle

spasms (10).

The actual damage that is done when someone suffers a strained back can

be quite variable. The muscles that support and move the spinal column may be

injured, the ligaments that connect the vertebral bodies together or form strong

capsules around the facet joints might be partially torn or a mild case of a slipped

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intervertebral disc may be the source of the pain. In each of these situations, the

human body is usually able to heal itself and will do so without surgery if given the

proper treatment.

There are many sources of low back pain involving the vertebrae,

intervertebral disks, and nerves. Low back pain caused by soft tissue problems is

likely to originate in one or more of three different locations: 1) Quadratus lumborum

and its adjacent structures. Quadratus lumborum is the muscle between the bottom

rib and the top of the pelvis. It is a key muscle in coordinating upper and lower body

movements. It is a deep muscle, situated underneath the lumbar paraspinal

muscles. Muscle problems are invariably accompanied by connective tissue

problems. This area, unprotected as it is by any skeletal structures, is thick with

connective tissue: the thoracolumbar fascia, the gluteal aponeurosis, and other

tough connective tissue cover and surround these muscles. 2) The buttock muscles.

These include the three gluteal muscles—gluteus maximus, medius and minimus—

and the deep lateral rotators of the hip, especially pyriformis. 3) Iliopsoas. This is the

primary hip flexor—its chief assistant being rectus femoris—running down through

the abdominal cavity and the groin to the lesser trochanter. But its origins are the

inner surface of the ilium (iliacus muscle) and the transverse processes of the

lumbar vertebrae, which mean that every lifting of the leg pulls on the pelvis and the

lumbar spine (11).

2.4. Risk Factors of Low Back Pain

Body measurements and overall posture of the driver, seat/workstation

design, long driving time, long distance driving, duration of employment, social and

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psychological factors and long term whole body and hand-arm vibration exposure

contribute to the development of low back pain.

Anthropometry is the study of human body dimensions. It includes body

volumes, masses of body segments, center of gravity and inertial properties (12).

Engineering anthropometry deals with the application of scientific physical

measurement methods to human subjects for the development of engineering

design standards (13). It includes static and functional measurements of dimensions

and physical characteristics of the body as they occupy space, move and apply

energy to physical objects. Static or structural body dimensions are taken with the

body of the subjects in fixed, standardized positions. Functional or dynamic body

dimensions are taken when the body of the subject is involved in some physical

movement (14).

Anthropometric measurements, such as leg length and weight, are factors to

be included in determining causation of low back pain among bus drivers. Unequal

lengths of both legs might contribute to posture, which if improper might significantly

lead to low back pain. Weight, on the other hand would influence how the spine

would support the body especially the upper back. Anthropometers, tapes and

scales are used to obtain measurement (14).

Another risk factor for LBP is height. It has been suggested that tall people

are at higher risk of having low back pain than short people (15). The average

heights for Filipino adults are as follows: those aged 60 and over, 153 centimeters or

five feet; those aged 40 to 59, 156.2 cm or 5 feet 1 inch; and those aged 20 to 39,

157.6 cm or 5 feet 2 inches. There were significant differences in the average

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heights by sex. Among those aged 20 to 39, the average height for men was 163.3

cm or 5 feet 4 inches (16).

Posture may be a factor causing LBP. It is a position or attitude of the body,

the relative arrangement of body parts for a specific activity, or a characteristic

manner of bearing one’s body (1).

Sitting posture also contributes to the development of low back pain.

Prolonged sitting may result in excessive loading and tissue deformation of the

lumbar spine (17).

The type of sitting posture also plays a role in reducing excessive stresses on

the spine which may lead to LBP. Flexed postures are advantageous, as flexion

results in increased fluid flow and improved transport of nutrients into the

intervertebral discs (18). This may decrease the likelihood of degenerative changes,

which have been associated with decreased metabolic transport in the disc (19).

A similar study also concluded that flexed postures are favorable when sitting

and when lifting heavy materials (20). In a population study on primitive cultures

who squat while sitting in a flexed position, it was found that there was decreased

incidence of degenerative changes in their lumbar spines (21).

On the other hand, a recent study supports the lordotic or extended position

for sitting as beneficial since this posture helps to balance the loads on various

spinal structures and prevents stressing the posterior ligaments (22, 25).

Sitting with the back slouched for as little as 20 minutes can result in

increased laxity of the posterior spinal ligaments. It may take 30 minutes or more for

these ligaments to regain their previous level of stiffness (22). Also, sitting with the

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spine in extension reduces the intradiscal pressure. Extension helps to cause the

nucleus to move anteriorly, thus helping to prevent and reduce the tendency for

posterior disc bulging and protruding (23).

Research has also shown that lumbar disc herniation may result from

prolonged sitting in the typical flexed posture (24).

Lordotic, extended position should be preferred for sitting over the flattened or

flexed posture. However, given that any sitting posture results in increased spinal

loading, frequent changes in posture from sitting to standing, etc., over the course of

a day is to be preferred for protecting the spine (17).

There are several sources of pain in postural problems. The ligaments, facet

capsules, periosteum of the vertebrae, muscles, anterior dura mater, dural sleeves,

epidural areolor adipose tissue and walls of blood vessels are innervated and

responsive in nociceptive stimuli. Also, mechanical stress to pain-sensitive

structures, such as sustained stretch to ligaments or joint capsules or compression

of blood vessels, causes distention or compression of the nerve endings that leads

to the experience of pain. This type of stimulus occurs in the absence of an

inflammation reaction. It is not a pathologic problem but a mechanical one. Relieving

the stress to the pain-sensitive structure relieves the pain stimulus and the person

no longer experiences pain. If the mechanical stresses exceed the supporting

capabilities of the tissues, breakdown will occur. If this continues without adequate

healing, overuse syndromes with inflammation and pain will affect function without

an apparent injury. Relieving the mechanical stress along with decreasing the

inflammation is important (23).

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Pain can come from muscles, ligaments, nerves, discs, or bones. People who

lead a sedentary lifestyle are especially at risk, because their bodies are not

conditioned. They are prone to strains when they use their backs. Other risk factors

include advancing age, frequent or heavy lifting, obesity, poor posture and repetitive

movements including twisting (26).

Seat/workstation design and posture may also be factors in the development

of low back pain. Driving is different from ordinary sitting in that the body is subject

to different forces such as accelerations and decelerations, lateral swaying from side

to side and whole body up and down vibrations while the vehicle is in motion (27).

Prolonged periods of driving in a constrained posture on a seat with poor ergonomic

design during a trip may result in de-conditioning, which is the weakening of the

muscles supporting the spine and trunk due to inactivity, less exercise, and lack of

balance. These muscles cannot fully withstand pressure or even support the spinal

cord to its normal position. Thus, the entire back becomes sore and tired (28).

There is growing evidence that the combination of these factors, coupled with the

design of the seat itself, may increase the risk and occurrence of back problems for

some people.

Ergonomics is an approach, which puts human needs and capabilities at the

focus of designing technological systems. The aim is to ensure that humans and

technology work in complete harmony, with the equipment and tasks aligned to

human characteristics. The term originated from the Greek words “ergon” which

means work and “nomos” which means natural laws (29).

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Ergonomics, also called human factors, is based on biological or natural

sciences. Its main components are anatomy, physiology, psychology, medicine, and

engineering.

The contribution of basic anatomy lies in improving the physical fit between

people and the things they use. Anthropometry provides data on the structure of

human body, in various postures. On the other hand, biomechanics considers body

responses, particularly the operation of muscles and limbs, when subjected to

various internal and external forces. It ensures that working postures are beneficial

and excessive forces are avoided (29).

Human physiology supports two technical areas. Work physiology focuses on

how the body functions when performing work. It addresses the energy

requirements of the body and sets standards for acceptable physical work rate and

workload and for nutrition requirements. Environmental physiology focuses on how

the body functions when subjected to climatological factors. It also includes analysis

of the impact of physical working conditions, such as thermal, noise and vibration,

and lighting, and sets the optimum requirements for these (29).

Psychology is concerned on the behavioral responses of human to work and

environment, particularly human information processing and decision-making

capabilities. It aids in the cognitive fit between people and the things they use (29).

Medicine is directed towards diagnosis of injuries, which can either be acute

or chronic. Lastly, engineering provides information on machinery and assists in its

adaptation for human use (30).

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Ergonomic stressors result from poor workplace designs. These stressors

may include the following: repetition, the number of motions or movements that are

performed per cycle or per shift; force, the power of the muscles used to produce

motion in order to perform necessary activities; and extreme postures, wherein

muscles are required to work at a level near or at their maximum capacity. Before

setting standard measurements and providing necessary seat adjustments,

ergonomic stressors and occurrence of possible health conditions should be

considered (31).

Musculoskeletal disorders are injuries of the soft tissues of the upper

extremities, shoulders and neck, lower back, and lower extremities that are primarily

caused or exacerbated by workplace risk factors, such as sustained and repeated

exertions or awkward postures and manipulations. Repetitive motion injury (RMI),

also known as repetitive stress injury, is a type of stress injury that results from

repetitive motions such as frequent bending or sustained awkward positioning

performed over extended periods of time without allowing for sufficient rest. RMI

includes medical conditions resulting from repeated use of a body part (31).

Ergonomics has a wide application to everyday situations with its significant

implications for efficiency, productivity, safety and health in work settings (29). The

different aspects of the workstation are then evaluated to determine if it fits the

person who works in it.

Workspace is the area within which a person performs the tasks that add up

to one’s job. Its physical design includes working out how much space is needed

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and positioning of furniture, tools, equipment and other items needed to perform

tasks, in respect with posture, access, clearance, reach and vision of the user (32).

The evaluation of the seating of Qantas flight deck crew showed that there is

a widespread postural discomfort due to insufficient room space and LBP during

flying among middle- and long-distance Qantas pilots (33). It was also found that an

unsuitable workspace that prevents employees from sitting in a balanced position

can cause poor body positions. The physical arrangement of work space elements

such as work surfaces, tools and equipment may not correspond with the reaches

and clearances of seated employees. The workstation may also be unsuitable

because the seats are too high or low for an employee's body size and shape.

These changes may ultimately lead to low back pain (34).

The ergonomic design of the driver’s workstation is a necessary component

of driver safety and health protection. The relative comfort and functional utility of

the driver’s seat is a consequence of their physical design in relation to the physical

structure and biomechanics of the human body (35).

The driver’s seat should be vertically and horizontally adjustable and have

adjustable lower back support and springs (36).

The height of the seat should be such as to avoid excessive pressure on the

thigh. The front edge of the seat should be a bit lower than the distance from the

floor to the thigh, when seated. It was recommended that the front edge be at least

2 inches below the popliteal crease, which is the crease at the back of the hollow

knee (37). The length and width of the seat would partly depend on the type of seat.

In general, the length should be set to be suitable for small persons in order to

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provide clearance for the calf of the leg and to minimize thigh pressure, and the

width should be set to be suitable for large persons (14).

The steering wheel should be adjustable along the axis of the steering

column. Possible adjustments in its angle of inclination can provide more comfort.

The pedals should have equal angles and be within easy reach for both short and

tall drivers (36).

The measurements of the workstation and the adjustments that can be made

should fall within a range that is applicable to all drivers. The adjustability and the

ways of adjusting the driver’s seat and steering wheel should be coordinated so

drivers within the design range can find positions for their arms and legs that are

comfortable and ergonomically healthy.

Seats should provide for correct curvature of the lumbo-sacral section of the

spine in order to keep the spinal column in a state of balance. Seats without or with

inadequate backrest may cause kyphosis, a forward-leaning posture produced by

excessive pressure between the vertebrae. The lordosis type of posture with

adequate lumbo-sacral back support represents a more desirable posture. An angle

of 90 degrees or less between the seat pan and backrest may cause pressure on

the lower lumbar discs and back muscles. The resultant forces contribute to LBP

and degeneration of the lumbar spine (14). Loss of rigidity and sagging of the seat

pan due to wear and tear results in elevation of the knee to a higher level which

causes gravity forces of the upper body to concentrate at the lower lumbar spine.

The seat surface should be more or less plane rather than shaped, although a

rounded front edge is highly desirable. Upholstery should be firm rather than soft.

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The covering materials should also be porous for ventilation and rough to aid

stability (38).

In order to establish a desirable posture, the angle of the seat and back

should be considered. The seat should be at a moderate angle and the back should

have an angle of from about 95 to 105 degrees or more with the seat. With

inclination of the backrest to at least 20 degrees, the amount of support needed to

balance the trunk is minimized and body weight is transferred to the backrest.

Adequate support for the lumbar area should also be taken into consideration. It is

important in preventing spinal complications and discomfort caused by angles

between the vertebrae (14).

A probable solution to LBP due to poor posture is the use of a lumbar pad

support. A study in the Philippines showed that use of lumbar pad support

significantly decreased the occurrence of LBP among taxi drivers. Thirty taxi drivers

with LBP due to poor posture were asked to use the pad support. The occurrence of

LBP among them was compared with a similar sample size not using lumbar pad

support (39). Lumbar pad supports can compensate for an ineffective postural seat

design which may contribute to tension and fatigue of driver.

Foot posture contributes to development of low back pain in that poor foot

posture can affect the ligaments of the lower limb and put more stress on the back

and knees. Driving involves active use of the feet—the right foot on the accelerator

pedal, the left on the brake and also on the clutch in a stick shift. When the feet are

active, they cannot be used to support and stabilize the lower body unlike ordinary

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sitting wherein the feet are rested on the floor. Poor quality or worn footwear do not

properly support the feet as well (40).

Long driving time refers to the length of time the driver spends at the wheel

while traveling. Continuous driving for four hours or more can increase the risk of

having low back pain. Driving with limited movements for a prolonged period or

sitting in one position for hours can aggravate back pain and even damage one’s

health because of fatigue and lack of exercise (41). A study found that after

accounting for all the possible psychological causes of back injury, drivers with the

San Francisco Municipal Railway (Muni) still have an elevated risk for injury that can

be attributed solely to their physical working conditions, particularly the number of

hours on the job. Drivers who worked full-time had more than twice as many back

injuries as those who worked part time (42).

Driving distance pertains to the interval, in kilometers, between the origin and

destination. Men drive an average of 71 kilometers and women 55 kilometers each

day (27). Long driving distance is applicable to buses, which travel from urban to

rural areas, and vice versa.

The duration of employment is the span of time or number of years a person

has been engaging his services as a driver of a company. This factor usually goes

with age. Young drivers have more acute episodes of back pain while older people

have more cases of chronic pain (43). High-risk occupations such as those with

exposure to whole body vibration caused by long distance driving, place workers at

risk for low back pain. The longer a person is on the job, the higher the risk (41).

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Epidemiologic studies on low back pain consistently show a strong correlation

with whole body vibration from motor vehicle driving (44). Other sources of vibration

may include rocky and bumpy roads, worn out shock absorbers and bus engines

that are not well-maintained. Vehicle vibration enters the driver's body through the

seat. The structural properties of automobile seats may be a source of LBP for the

driver. Because of the strong coupling between the seat backrest and the vehicle

floor, a differential motion between backrest and seat cushion occurs when driving. It

inevitably induces continuous strains in the lower lumbar spine of the seat occupant

and is therefore a possible source of low back pain (45).

Two general categories of vibration impinging on humans are whole body

vibration or WBV (vibration transmitted to the entire body through some support

such as a vehicular seat or building floor); and segmental (e.g. hand-arm) vibration

(vibration locally applied to specific body parts such as hands and arms from a

vibrating hand tool). Bus drivers, among others, are exposed to both types of

vibration. The vehicle moving and hand-arm vibration cause whole body vibration by

contact with the gear stick when shifting gears (46).

A British study found exposure to hand-transmitted vibration and finger

blanching and sensory symptoms to be significantly associated. There was no

marked excess of LBP complaints in workers exposed to WBV, with only moderate

excesses in men exposed above the British Standard and male riders of heavy

industrial vehicles (47).

Whole body vibration exposure is another risk factor for low back pain. In a

questionnaire survey of back pain symptoms in professional truck drivers, three

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factors were found to be related significantly to the prevalence of LBP. These were

irregular duty time, short resting time and long driving time in a day (9). Evidence

also shows that while LBP is age-related, it is also occurring earlier than expected

for workers exposed to whole body vibration (48). Whole body vibration is related to

prolonged sitting posture, poor working posture and inadequate working conditions

in contributing to low back pain (49).

A number of studies have been conducted on the association of vibration

exposure and low back pain. It was found that the occurrence of low back

symptoms increased with increasing whole body vibration exposure in terms of total

or lifetime vibration dose, equivalent vibration magnitude and duration of exposure

from years of service. Frequent awkward exposures are also related to some types

of low back symptoms. Moreover, risk may be due to both whole body vibration

exposure and prolonged sitting in a constrained posture (50). However, it was

determined that in many working situations with a daily exposure of eight hours or

more, suspension seats—conventional or air—will not protect drivers from harmful

exposure to whole body vibration (51).

To measure the level of exposure quantitatively, a vibration signal is first

collected using vibration pickup devices, which are usually placed on machinery

bearing caps. The caps are an ideal place for pick-ups because of their accessibility

and because they are the points through which vibration transmits the most readily.

For each point, the vibration signal picked up is then recorded in a vibration meter or

vibration analyzer. A vibration meter will allow defect determination, but to analyze

the cause, a vibration analyzer is needed (52).

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Psychological factors play a role in the three phases of LBP—onset of pain,

perception of pain and chronic pain. Recent research shows that in many people,

preexisting depression and the inability to cope may be more likely to predict the

onset of pain than physical abnormalities. Moreover, social and psychological

factors play a part in the severity of pain a person experiences. Depressed people

are more likely to experience vague physical symptoms, including LBP. In a study of

truck and bus drivers, almost all the truck drivers liked their work and their bosses

while bus drivers stated much lower job satisfaction. 50% of the truck drivers

reported LBP but only 24% lost time at work. Bus drivers with LBP had a significantly

higher absentee rate in spite of less stress on their backs. A related study found that

pilots who generally reported high job satisfaction reported much fewer back

problems than their flight crews. Another study stated that low rank, low social

support and high stress in soldiers were associated with a higher risk for disabling

back pain. Also, the way a patient perceives and copes with pain at the beginning of

an acute attack may in fact condition the patient to either recover or develop a

chronic condition. Those who over-respond to pain tends to feel out of control and

discouraged, increasing their risk for long-term problems. A study found that among

patients with back problems, the fear of pain was actually more disabling than the

pain itself (53).

Depression, low activity or high pain behavior, negative beliefs or fear of pain

are three psychological-behavioral factors that consistently show a significant

relationship with LBP. However, it has not been determined which of these factors is

greatly involved in predicting disabling LBP (54).

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Emotional factors which increase experienced pain include anxiety, anger and

depression. Specific psychological factors that can increase pain are degree of focus

on the pain, boredom, beliefs about the meaning of the pain and a sense of poor

control over pain (55).

Psychological factors are important in people with chronic low back pain.

Dissatisfaction with a work situation, the management, or a job and boredom

contribute significantly to the onset and persistence of LBP (56).

The research on Muni drivers, led by Niklas Krause, showed that physical and

psychosocial conditions in the workplace play a role in causing back injury. The

research also found that after accounting for physical work load, a stressful job with

high psychological demands, low satisfaction and low supervisor support can cause

spinal injury (42).

There are many other factors not related to driving which should also be

considered in LBP. For ages 20-60, a herniated disc may be the cause of LBP.

Other possible causes are myofascial pain, spondylolysis, fracture, facet syndrome,

stenosis, fibromyalgia, infection, spondyloarthropathy, and tumor (57).

LBP can also be caused by referred pain. Referred pain is pain caused by

one part of the body and is also perceived in another distant part of the body not

directly involved with the cause. Most common sources of referred pain to the low

back are the organs in the abdomen, pelvis and retroperitoneal space, such as

stomach, intestines, uterus and ovaries and kidneys. For example, pain of peptic

ulcer, diverticulitis of the colon, pelvic inflammatory disease, acute prostates and

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trochanteric bursitis (inflammation of the bursa of the hip area) can refer pain to the

low back (58).

Low back pain is a persistent global problem and everyone is susceptible. Its

prevalence is consistently similar across countries. It has been studied extensively

and has been shown to be possibly be prevented with the right measures. Still, the

problem remains unsolved.

In the Philippines, no studies have been done on LBP among bus drivers.

Several studies have been done on LBP, but of different population other than bus

drivers. This study would contribute to the pool of knowledge already available

regarding LBP status in the Philippines and possibly that of Southeast Asia.

Preventive measures may be designed in order to address the current situation of

the LBP among Filipino male bus drivers.

3.0 Objectives of the Study

General Objective: To identify risk factors associated with low back pain among bus

drivers.

Specific Objectives:

1. Describe the distribution of bus drivers according to age, long driving time,

vibration exposure, long distance driving, driving posture, seat/workplace

design and psychological factors.

2. Describe the distribution of bus drivers with low back pain by age, long driving

time, vibration exposure, long distance driving, driving posture,

seat/workplace design and psychosocial aspects.

23

3. Determine the risk factors of low back pain adjusting for the effects of

confounders.

4.0 Significance of the Study

Studies in the Western countries have shown that vehicle drivers—trucks,

buses, taxis—are at an increased risk of developing low back pain, with contributing

factors such as long driving time, whole body vibration exposure, long distance

driving, ergonomics, age, duration of employment and psychological factors.

However, there are no known studies conducted in the Philippines to look into the

effects of these factors to the development of low back pain among Filipino bus

drivers.

This study will determine if an association exists between the risk factors and

low back pain among Filipino bus drivers. Driving would expose the drivers to long

periods of experiencing vibration, poor ergonomic conditions, long distance travel

and long driving time, causing low back pain. Necessary measures can then be

recommended that will alleviate and/or prevent low back pain, which would benefit

the bus drivers in terms of better health as well as the companies in terms of

increased productivity.

24

25

6.0 Materials and Methods

6.1 Study Design

An analytical cross-sectional study was done in 8 bus companies

located along Gil Puyat Avenue and Epifanio delos Santos Avenue at Pasay

City. Preliminary visits and discussion with managers were performed in

order to gather preliminary data on the feasibility of the study and to ask initial

permission to be able to implement the study.

6.2 Study Population

The study included as its subjects Filipino male air-conditioned bus

drivers from 8 bus stations. Non-airconditioned bus drivers were not included

in order to maintain the homogeneity of the subjects. Also, according to the

bus company managers, air-conditioned bus drivers more often complain

about low back pain (LBP) than non-airconditioned bus drivers and therefore,

it is expected to have more cases of LBP.

Several studies in other countries have shown a low back pain

prevalence of about 50% (9). Initial interviews with the bus drivers and

supervisors also showed that LBP is a common medical complaint of drivers.

Based on these, the sample size was computed as follows:

P = 0.5662 α or d = 0.05 Z α = 1.96 Q = 1- P n = PQZ2

d2

P = proportion of bus drivers with chronic low back pain Q = 1 – P Z = normal variate Z α = 1.96 where α = 0.05

α = maximum allowable error

26

n = 0.5662 x 0.4338 x (1.96) 2

(0.05) 2

n = 377.4 = 378 subjects

Proportional allocation was done to assure proper presentation of each

bus company in the study. Using the formula Pax = ( n1 / T) x n, the number

of subjects per bus station was computed as follows:

where:

Pax = proportionally allocated sample size per bus (x1, x2,…,xn)

company

n1 = total number of drivers per company

T = total number of bus drivers from all the companies

n = computed sample size

n = Pax1 + Pax2 + … + Pax10

The following were the computed proportionally allocated sample size per bus

station:

• Tritran Bus Company – 31

• Grand Star Coach Bus Company – 8

• Green Star Bus Company – 51

• JAC Liner – 4

• BBL Transportation Systems Inc. – 16

• Victory Liner – 75

• Pangasinan Five Star Bus Company, Inc. – 118

• Philtranco – 74

27

6.3 Data Collection

The group sent a letter to each bus company management, which

stated the objectives of the study and asked for their permission to allow their

company to be included in the study. The group also verified the initial data

about the number of drivers employed in each company.

The researchers went to the bus stations everyday for three weeks,

depending on a schedule, which was prepared, based on the availability of

drivers. Drivers were approached while they were taking a break or waiting

for their buses to get full. The information and consent form was given for

signature and a self-administered questionnaire was given to each driver

afterwards. A group member (S1) provided assistance and answered queries

from drivers when necessary. In addition, the same student quickly edited

accomplished questionnaires. While the questionnaires were being

answered, the corresponding bus and bus seat/workplace dimensions were

measured by two other members (S3 and S4) of the group. The subjects

were also asked to show their usual driving posture by sitting on the bus

driver’s seat. Leg reach to the pedal, arm reach to the steering wheel and

reclining angle were measured. Anthropometric measurements (leg length,

arm length and weight) were measured by another member of the group (S2)

after the subjects have finished answering the questionnaires assisted by S1.

Exposure of the drivers to vibration was measured qualitatively using the

questionnaire.

28

6.4 Data Collection Tools

Assisted Self-Administered Questionnaire

This was used to determine demographic data and information

about driving time, driving distance, driving posture, duration of

employment as a driver and psychosocial factors.

Measuring Tape

Leg length, arm length and seat / workstation dimensions were

taken using a measuring tape. This data was important to relate body

posture and seat design in relation to LBP.

Protractor

This was used to measure the reclining angle of the seat.

Weighing Scale

This was used to estimate the subject’s weight. This data was

important since it had an effect on the force exerted on the lower back

when the person is sitting or standing.

6.5 Data Processing

From the data gathered, a coding manual was prepared. Data was

encoded using Epi-Info Software version 6.0 and Statistical Package for

Social Sciences (SPSS) version 10.0 available in the group’s personal

computer. These data were processed into tables and graphs for better

visual analysis.

29

6.6 Data Analysis

The risk factors included were vibration exposure, rough roads, long

driving time, long distance driving, uncomfortable sitting posture, insufficient

room space, constrained driving posture, seat design and psychological

factors. The prevalence of LBP among the subjects was also computed. Chi

square test and logistic regression were used to test for the association of risk

factors and low back pain. Finally, multivariate analysis was performed with

the use of SPSS using backward-Wald method.

6.7 Operational Definition of Variables

Dependent variable:

1. Low Back Pain – chronic pain localized in the lumbo-sacral spine with

an acute and sudden onset lasting for about thirty minutes and is

intermittent and recurring for at least six months.

Independent variables:

1. Long Distance Driving – driving distances wherein low back pain is felt

2. Long Driving Time – driving for more than four hours everyday

according to a study on bus drivers in Lithuania

30

3. Duration of employment – this is the span of time (number of months

and years) a person has been engaging his services as a bus driver.

4. Posture – a position of attitude of the body, the relative arrangement of

body parts while driving which includes reclining angle, sitting, arm,

and leg position

5. Psychological Factors – depression, low activity or high pain behavior,

negative belief, or fear of pain

6. Depression – feeling down or unhappy with working conditions or

family problems related to mental stress

7. Boredom – state of being uninterested because of frequent exposure

to long hours of driving

8. Constrained posture – inability to maintain a comfortable sitting

position while driving

9. Abnormal vibration – unusual vibration due to poorly maintained buses

10. Vibration exposure – exposure to vibration for more than 4 hours a

day, abnormal vibration complaint, with at least 20% rough roads

experienced

Confounding variables:

1. Seat / workstation Design – the overall make-up of the drivers’ seat in

relation to easing low back pain and other injuries which include the

reclining angle of back seat and overall adjustability

2. Age – number of years lived of subject since last birthday.

31

Other definitions:

1. Pain – unpleasant sensory experience associated with actual negative

potential tissue damage or described in terms of such damage.

2. Anthropometry – dealing with measurement of leg length, arm length,

and weight

3. Work – an activity in which one exerts strength or faculties to do or

perform a labor, task, or duty that affords ones accustomed means of

livelihood

7.0 Ethical Considerations

An informed consent form was prepared which explained all the information

about the study and was signed by each participant. Any information obtained

from the drivers employed in the different bus companies were kept confidential.

The study is not obliged to provide treatment for identified cases of low back pain

(LBP). Instead, any form of intervention will remain as the bus companies’

responsibility upon giving them the results of the study.

8.0 Assumptions, Strengths and Limitations

This study presupposed that all answers to the questions provided to bus

drivers are truthful and reliable.

The strength of this study is related to the fact that no similar studies

locally have been done in the past. The results of the study can serve as basis

for future researches among bus drivers in a larger scale. In addition, aside from

32

presenting low back pain among bus drivers, companies will also benefit in terms

of less worker absence and improved productivity once low back pain complaints

are reduced.

Only air-conditioned bus drivers were included in the study. Simple

random sampling was not done in the selection of the bus drivers for reasons

that their schedules are not fixed and they usually are on a rotation basis.

Drivers also come at different times and based on the limited time available for

data collection, waiting for the driver based on the selection by random sampling

will not allow fulfillment of the sample size required. The subject’s availability

during the scheduled visits of the researchers and willingness to participate were

instead used as criteria for participation. A great degree of selection bias was not

expected since the bus drivers were informed that no treatment would be

provided if found with low back pain. Thus, drivers with low back pain were not

expected to volunteer which will unduly increase the number of LBP cases. In

addition, personal characteristics and risk factors were elicited which were

controlled for in the data analysis using logistic regression. Vibration exposure

was measured qualitatively using a questionnaire due to the unavailability of a

vibration meter for a quantitative measurement. However, the study attempted to

put together several risk factors affecting exposure to vibration such as seat

design and exposure to rough roads.

Based on the recommendation of the study’s ergonomics adviser,

quantitative analysis of anthropometric and ergonomic data cannot be performed

33

due to limitations of time and data gathered. However, these data will be kept

for future use in related studies.

9.0 Results and Discussion

After data collection, the data were presented based on univariate, bivariate

and multivariate analysis.

9.1 Univariate Analysis

Figure 1. Civil Status of Subjects

4%

Single1%95% Married

0% Separated Widowed 95% of the drivers are married. Table 1. Insufficient workspace experience

Insufficient workspace Frequency Percentage No 143 37.8 Yes 235 62.2

A little over 60% of the drivers complained of experiencing insufficient workspace. Figure 2. Abnormal vibration

81%

19%YesNo

81% of the drivers experienced abnormal vibration due to their current job.

Table 2. Uncomfortable sitting posture Uncomfortable sitting posture Frequency Percentage

No 145 38.4 Yes 233 61.6

A little over 60% of the drivers experienced uncomfortable sitting posture at their workstation.

34

Figure 3. Constrained posture

68%

32%

YesNo

Nearly 70% of the drivers had constrained posture at the workstation. Table 3. Rough roads

Rough roads Frequency Percentage No 20 5.3 Yes 358 94.7

Almost 95% of the drivers experienced rough roads while driving. Figure 4. Boredom

74%

26%

YesNo

74% of the drivers experienced boredom while driving. Table 4. Depression

Depression Frequency Percentage No 154 40.7 Yes 224 59.3

Nearly 60% of the drivers had experienced depression. Figure 5. Frequent movement of back

92%

8% YesNo

A little over 90% of the drivers move their backs frequently while driving. Table 5. Frequent movement of arms

Frequent movement of arms Frequency Percentage No 36 9.5 Yes 342 90.5

Almost 91% of the drivers frequently move their arms while driving.

35

Figure 6. Frequent movement of shoulders

96%

4% YesNo

96% of the drivers frequently move their shoulders while driving. Table 6. Frequent movement of feet

Frequent movement of feet Frequency Percentage No 31 8.2 Yes 347 91.8

92% of the drivers frequently move their feet while driving. Figure 7. Back pain experience 14% Yes

No 86%

86% of the drivers experienced back pain. Table 7. Upper back pain experience

Upper back pain Frequency Percentage No 256 67.7 Yes 122 32.3

32% of the drivers experienced upper back pain. This comprises about 37% of all back pain complaints. Table 8. Mid back pain experience

Mid back pain Frequency Percentage No 318 84.1 Yes 60 15.9

16% of the drivers experienced mid back pain. This comprises almost 20% of all back pain complaints. Table 9. Low back pain experience

Low back pain Frequency Percentage No 120 31.7 Yes 258 68.3

68% of the subjects experienced low back pain. This comprises almost 80% of all back pain complaints.

36

99% 1% YesNo

Figure 8. Rest period Almost all of the drivers have rest periods in between trips. Table 18. Work Satisfaction

Work Satisfaction Level Number Percentage I like my job 334 88.4

Just right 44 11.6 I don’t like my job 0 0

Others 0 0 All of the drivers are satisfied with their work. Figure 9. Employee satisfaction with management

27%

50%

13%

10%I Am HappyI LikeI Don't LikeI Am not Happy

A little over 75% of the drivers are satisfied with management. Table 11. Relationship with co-workers

Relationship Number Percentage Good 313 82.8

Just right 63 16.7 Difficult 1 0.3 Others 1 0.3

Almost all have good relationship with co-workers.

16%54%

20%

10% HappyEnoughNot EnoughNot Happy

Figure 10. Salary satisfaction

70% of the drivers are satisfied with their salaries.

37

Table 12. Seat design Type of Seat Design Frequency Percentage

With cushion and with lumbar pad support 292 77.2 With cushion but without lumbar pad support 83 22 Without cushion but with lumbar pad support 0 0

Without cushion and without lumbar pad support 0 0 Others 3 0.8

Almost 80% of the driver seats are cushioned and have lumbar pad supports. Figure 11. Driving posture

45%

47%8% Reclined

StraightStooped

45% of the drivers have reclined driving posture. 47% have straight posture while driving. Only about 10% have stooped driving posture. Table 13. Seat reclinability

Reclinability Frequency Percentage No 175 36.3 yes 203 53.7

Almost 55% of the driver seats can be reclined. Figure 12. BMI

1%

36%

52%11%

Underweight (< 18.5)

Healthy Weight (18.5-24.9)

Overweight (25-30)

Obese (>30)

A little over 60% of the drivers exceeded the normal BMI. Only 36% met the normal BMI.

38

Table 14. Age Group Age group Frequency Percentage

20-24 49 13 25-29 60 15.9 30-34 45 11.9 35-39 70 18.5 40-44 70 18.5 45-49 58 15.3 50-54 20 5.3 ≥ 55 6 1.6

A little over 90% of the drivers are aged 20-49. The age group 35-44 comprises almost 40% of the drivers. Table 15. Number of years employed

Number of years Frequency Percentage 0-4 32 8.5 5-9 62 21.7

10-14 172 45.5 15-19 29 7.7 20-24 30 7.9 25-29 21 5.6 > 30 12 3.2

45% of the drivers have been employed for 10-14 years as bus drivers.

4%

7%

19%

41%

24%

3%

2%

100-199 200-299

300-399 400-499

500-599 600-699

> 700

Figure 13. Long distance driving 42% of the drivers drive from 400-499 kilometers per day. Figure 14. Vibration Exposure 35%

Yes No

65% 65% of the drivers are exposed to vibration while driving.

39

Table 16. Long driving time Hours Frequency Percentage

< 8 15 4 9-10 28 7.4 11-12 124 32.6 13-14 84 22.2 15-16 61 16.1 17-18 39 10.3 ≥ 19 27 7.1

A little over 30% of the drivers drive from 11-12 hours per day while 56% drive at least 13 hours per day. Table 17. Frequency of low back pain in a day in hours

Hours Frequency Percentage < 0.5 126 33.3 0.5-5 195 51.6 6-10 26 6.9 > 10 31 8.2

A little over 50% of the drivers experience LBP from 30 minutes to 5 hours a day. Table 18. Frequency of LBP in a week Frequency of Low Back Pain

in days per week Number Percentage

1-2 249 65.9 3-4 54 14.3 5-7 75 19.8

About 65% of the drivers experience LBP once to twice a week.

33%9%

13%

13%

10% 6%

2%

9%

5%

0 > 0 - < 1

1-1.99 2-3.99

4-5.99 6-7.99

8-9.99 10-11.99

> 12

Figure 15. Duration of LBP experience in years

36% of the drivers have experienced LBP from one to less than six years. A little over 30% did not experience LBP at all. Table 19. LBP cases

Cases of LBP Number Percentage No 144 38.1 Yes 234 61.9

A little over 60% of drivers have LBP.

40

Figure 16. Rough roads experienced

27%34%

18% 9%12%

< 20 20-39

40-59 60-79

> 80

A little over 60% of the drivers experience less than or equal to 39% of rough

roads. Table 20. Weight

Kilograms Frequency Percentage 45-54 8 2.1 55-64 59 15.6 65-74 138 36.5 75-84 120 31.7 85-94 38 10.1 > 95 15 4

Almost 70% of the drivers weigh from 65-84 kilograms. Table 21. Height

Centimeters Frequency Percentage < 159 27 7.1

160-160.9 18 4.8 161-161.9 16 4.2 162-162.9 16 4.2 163-163.9 28 7.4 164-164.9 15 4 165-165.9 23 6.1 166-166.9 15 4 167-167.9 28 7.4 168-168.9 34 9 169-169.9 17 4.5 170-170.9 26 6.9 171-171.9 21 5.6 172-172.9 12 3.2 173-173.9 23 5.1 174-174.9 11 2.9

> 175 48 12.7 Almost 30% of the drivers have heights from 167 to less than 171 centimeters.

41

Figure 17. Seat reclining degree

3%

31%

31%

6% 16%

7%

6%

< 95 95-97

98-100 101-103

104-106 107-109

> 110

About 60% of the seats are reclined from 95 to 100 degrees. Table 22. Number of buses driven out of 10 buses with adjustable seats toward and away from the wheel

Number of buses Frequency Percentage 0-1 32 8.5 2-3 18 4.8 4-5 19 5 6-7 9 2.4 8-9 36 9.5 10 264 69.8

Almost 10% of the drivers have driven buses without adjustable seats. Table 23. Number of buses driven out of 10 buses with reclinable seats

Number of buses Frequency Percentage 0-1 126 33.3 2-3 17 4.5 4-5 20 5.9 6-7 10 2.6 8-9 31 8.2 10 174 46

A little over 33% of the drivers have driven buses without reclinable seats.

42

9.2 Bivariate Analysis

A. Results

Pearson chi square test was used to determine the association of risk factors

with low back pain. Significant associations were based on a 5% level. A p-value cut

off of ≤ 0.2 was used for all independent variables which will subsequently be

included in the multivariate analysis. A summary of the results of the Pearson chi

square test for association is shown below.

Table 24-A. Summary of Variables Cross-Tabulated with LBP Using Chi Square Test for Association with P value of ≤ 0.2

Association between

Independent variable Dependent Variable

Chi square

P value Remarks

1. Constrained posture LBP 24.89 0.000 Significant Association 2. Uncomfortable sitting posture LBP 11.05 0.001 Significant Association 3. Frequent movement of shoulders

LBP 8.08 0.004 Significant Association

4. Long distance driving LBP 16.59 0.011 Significant Association 5. Boredom LBP 6.04 0.014 Significant Association 6. Depression LBP 5.45 0.020 Significant Association 7. Insufficient work space LBP 5.18 0.023 Significant Association 8. Long driving time LBP 4.229 0.040 Significant association 9. Abnormal vibration LBP 4.08 0.043 Significant Association 10. Frequent movement of back

LBP 3.95 0.047 Significant Association

11. Employee satisfaction with management

LBP 6.02 0.110 No Significant Association

12. Height LBP 21.80 0.150 No Significant Association 13. Percent of rough roads LBP 6.67 0.154 No Significant Association 14. Vibration exposure LBP 1.91 0.167 No Significant Association 15. Rough roads LBP 1.86 0.173 No Significant Association

Table 24-B. Summary of Variables Cross-Tabulated with LBP Using Chi Square Test for Association with P value of > 0.2

Association between

Independent Variable Dependent Variable

Chi square

P value Remarks

1. Years of education LBP 0.93 0.335 No Significant Association 2. Consultation with doctor after injury

LBP 2.18 0.337 No Significant Association

43

3. Injury to right shoulder LBP 2.18 0.337 No Significant Association 4. Injury to both arms LBP 2.18 0.337 No Significant Association 5. Seat base length LBP 10.05 0.346 No Significant Association 6. Duration of employment LBP 6.44 0.375 No Significant Association 7. Injury to right foot LBP 1.88 0.391 No Significant Association 8. Accident experienced LBP 0.65 0.419 No Significant Association 9. Salary satisfaction LBP 2.67 0.445 No Significant Association 10. Accident injury LBP 1.47 0.479 No Significant Association 11. Frequent movement of arm LBP 0.42 0.519 No Significant Association 12. Injury to left leg LBP 1.24 0.537 No Significant Association 13. Sprain LBP 1.24 0.537 No Significant Association 14. Civil status LBP 2.06 0.559 No Significant Association 15. Seat adjustability towards and away from the steering wheel

LBP 0.34 0.559 No Significant Association

16. Job training LBP 0.32 0.570 No Significant Association 17. Length of training for current job

LBP 3.76 0.585 No Significant Association

18. Type of seat LBP 0.22 0.63 No Significant Association 19. Self training LBP 0.89 0.641 No Significant Association 20. Injury to chest LBP 0.68 0.712 No Significant Association 21. Injury to back LBP 0.68 0.712 No Significant Association 22. Injury to right thigh LBP 0.68 0.712 No Significant Association 23. Reclining degree of seat LBP 3.68 0.720 No Significant Association 24. Weight LBP 2.86 0.721 No Significant Association 25. Relationship with co- workers

LBP 1.3 0.729 No Significant Association

26. Training from current job LBP 0.6 0.742 No Significant Association 27. Body mass index LBP 1.08 0.783 No Significant Association 28. Frequent movement of feet LBP 0.07 0.790 No Significant Association 29. Work satisfaction LBP 0.06 0.800 No Significant Association 30. Inclination of seat LBP 0.06 0.804 No Significant Association 31. Training from previous job LBP 0.41 0.815 No Significant Association 32. Driving position LBP 0.37 0.830 No Significant Association 33. Injury to left arm LBP 0.33 0.847 No Significant Association 34. Injury to both shoulders LBP 0.03 0.859 No Significant Association 35. Injury to left thigh LBP 0.03 0.859 No Significant Association 36. Injury to both thighs LBP 0.33 0.859 No Significant Association 37. Injury to right knee LBP 0.03 0.859 No Significant Association 38. Injury to left knee LBP 0.03 0.859 No Significant Association 39. Injury to both knees LBP 0.33 0.859 No Significant Association 40. Injury to right leg LBP 0.03 0.859 No Significant Association 41. Injury to both legs LBP 0.03 0.859 No Significant Association 42. Injury to left foot LBP 0.33 0.859 No Significant Association 43. Injury to both feet LBP 0.03 0.859 No Significant Association 44. Dislocation LBP 0.03 0.859 No Significant Association 45. Muscle strain LBP 0.03 0.859 No Significant Association 46. Fracture LBP 0.29 0.864 No Significant Association 47. Injury to right arm LBP 0.18 0.913 No Significant Association 48. Age LBP 1.97 0.962 No Significant Association 49. Number of buses out of 10 buses with reclining seats

LBP 0.61 0.988 No Significant Association

44

Fifteen independent variables cross-tabulated with LBP were found to have a

p-value of ≤ 0.2 using Chi square test for association. These were, constrained

posture, abnormal vibration, vibration exposure, uncomfortable sitting posture,

boredom, depression, frequent movement of back, frequent movement of shoulders,

long distance driving, long driving time, insufficient workspace, employee satisfaction

with management, percent of rough roads, rough road experience and height.

Variables with a p-value of ≤ 0.2 were included for purposes of logistic regression

analysis. The following are the cross tabulations of the independent variables with

LBP.

Table 25. Relationship of Insufficient Work Space and LBP Insufficient Work Space Low Back Pain

No Yes Frequency Percentage Frequency Percentage

No 65 45.8 77 54.2 Yes 79 33.5 157 66.8

Chi square = 5.18 P value = 0.02287480 There is a significant relationship between insufficient room space and LBP. Table 26. Relationship of Abnormal Vibration and LBP

Abnormal Vibration Low Back Pain No Yes Frequency Percentage Frequency Percentage

No 35 49.3 36 50.7 Yes 109 35.5 198 64.5

Chi square = 4.08 P value = 0.04328993 There is a significant relationship between abnormal vibration and LBP. Table 27. Relationship of Uncomfortable Sitting Posture and LBP Uncomfortable Sitting Posture Low Back Pain

No Yes Frequency Percentage Frequency Percentage

No 71 49.0 74 51 Yes 73 31.3 160 68.7

Chi square = 11.05 P value = 0.00088653 There is a significant relationship between uncomfortable sitting posture and LBP.

45

Table 28. Relationship of Constrained Posture and LBP Constrained Posture Low Back Pain

No Yes Frequency Percentage Frequency Percentage

No 69 56.6.0 53 43.4 Yes 75 29.3 181 70.7

Chi square = 24.89 P value = 0.00000061 There is a significant relationship between constrained posture and LBP. Table 29. Relationship of Rough Roads and LBP

Rough Roads Low Back Pain No Yes Frequency Percentage Frequency Percentage

No 11 55.0 9 45 Yes 133 37.2 225 62.8

Chi square = 1.86 P value = 0.17285062 There is no significant relationship between rough roads and LBP. Table 30. Relationship of Percent of Rough Roads and LBP

Percent Low Back Pain No Yes Frequency Percentage Frequency Percentage

<20 45 43.7 58 56.3 20-39 45 35.2 83 64.8 40-59 24 35.8 43 64.2 60-79 17 51.5 16 48.5 ≥80 13 27.7 34 72.3 Chi square = 6.67 P value = 0.15420584 There is no significant relationship between percent of rough roads traveled and LBP. Table 31. Relationship of Boredom and LBP

Boredom Low Back Pain No Yes Frequency Percentage Frequency Percentage

No 48 49.0 50 51.0 Yes 96 34.3 184 65.7

Chi square = 6.04 P value = 0.01400367 There is a significant relationship between boredom and LBP.

46

Table 32. Relationship of Depression and LBP Depression Low Back Pain

No Yes Frequency Percentage Frequency Percentage

No 70 45.5 84 54.5 Yes 74 33.0 150 67.0

Chi square = 5.45 P value = 0.01953236 There is a significant relationship between depression and LBP. Table 33. Relationship of Frequent Movement of Back and LBP

Movement of Back Low Back Pain No Yes Frequency Percentage Frequency Percentage

No 17 56.7 13 43.3 Yes 127 36.5 221 63.5

Chi square = 3.95 P value = 0.04690682 There is a significant relationship between frequent movement of back and LBP. Table 34. Relationship of Frequent Movement of Shoulders and LBP

Movement of shoulders Low Back Pain No Yes Frequency Percentage Frequency Percentage

No 12 75.0 4 25.0 Yes 132 36.5 230 63.5

Chi square = 8.08 P value = 0.00446599 There is a significant relationship between frequent movement of shoulders and LBP. Table 35. Relationship of Long Driving Time and LBP

Number of hours driven Low Back Pain No Yes Frequency Percentage Frequency Percentage

< 8 9 64.3 5 35.7 > 8 135 37.1 229 62.9 Chi square = 4.229 P value = 0.040 There is a significant relationship between long driving time and LBP.

47

Table 36. Relationship of Long Distance Driving and LBP Distance (in kilometers) driven Low Back Pain

No Yes Frequency Percentage Frequency Percentage

100-199 9 64.3 5 35.7 200-299 15 53.6 13 46.4 300-399 25 35.7 45 64.3 400-499 52 33.1 105 66.9 500-599 40 44.9 49 55.1 600-699 3 27.3 8 72.7 ≥700 0 0 9 100 Chi square = 16.59 P value = 0.01093037 There is a significant relationship between long distance driving and LBP. Table 37. Relationship of Vibration Exposure and LBP

Vibration Exposure Low Back Pain No Yes Frequency Percentage Frequency Percentage

No 57 43.2 75 56.8 Yes 87 36.4 159 64.6 Chi square = 1.91 P value = 0.16738501 There is no significant relationship between vibration exposure and LBP. Table 38. Relationship of Employee Satisfaction with Management and LBP

Employee Satisfaction with Management

Low Back Pain

No Yes Frequency Percentage Frequency Percentage

I am happy 43 42.2 59 57.8 I am satisfied 76 40.9 110 59.1

I am not satisfied 16 31.4 35 68.6 I am not happy 9 23.1 30 12.8

Chi square = 6.02 P value = 0.11045317 There is no significant relationship between employee satisfaction with management and LBP. Table 39. Relationship of Height and LBP

Height Low Back Pain No Yes Frequency Percentage Frequency Percentage

< 159 7 25.9 20 74.1 160 6 33.3 12 66.7 161 8 50.0 8 50.0 162 7 43.8 9 56.3 163 9 32.1 19 67.9

48

164 3 20 12 80 165 7 30.4 16 69.6 166 7 46.7 8 53.3 167 13 46.4 15 53.6 168 8 23.5 26 76.5 169 5 29.4 12 70.6 170 14 53.8 12 46.2 171 11 52.4 10 47.6 172 5 41.7 7 58.3 173 10 43.5 13 56.5 174 1 9.1 10 90.9

> 175 23 47.9 25 52.1 Chi square = 21.80 P value = 0.14962400 There is no significant relationship between height and LBP. B. Discussion

Factors such as employee satisfaction with management, height, rough

roads, vibration exposure and rough road complaints were found not to be

significantly associated with LBP in the bivariate analysis. However, the p values of

these variables were within 0.06 – 0.20. Review of related literature showed strong

correlation of these variables with low back pain. Thus, they were included in the

multivariate analysis.

1. Insufficient Work Space

Results show that insufficient room space is associated with low back pain.

This is consistent with a study evaluating the seating of Qantas flight deck

crew which showed that postural discomfort due to insufficient room space and low

back pain during flying among middle- and long-distance Qantas pilots were

widespread (33).

An unsuitable workspace that prevents employees from sitting in a balanced

position can cause poor body position. The physical arrangement of workspace

elements such as work surfaces, tools and equipment may not correspond with the

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reaches and clearances of seated employees. The workstation may also be

unsuitable because the seats are too high or low for an employee's body size and

shape. These changes may ultimately lead to low back pain (34).

2. Abnormal Vibration (Whole Body Vibration)

A significant association was also observed between abnormal vibration and

low back pain.

Although reports of low back pain were found to be age-related, there was

evidence that low back pain occurs earlier than expected for workers exposed to

whole body vibration (WBV). WBV is also related to poor working posture,

prolonged sitting posture and inadequate working conditions and contribute to the

occurrence of low back pain (48).

In a related study, a significant relationship was also found between exposure

to hand-transmitted vibration and sensory symptoms. There was no marked excess

of low back pain complaints in workers exposed to WBV, with only moderate

excesses in men exposed above the British Standard and male riders of heavy

industrial vehicles (47).

3. Uncomfortable Sitting Posture

Uncomfortable sitting posture was also observed to be associated with low

back pain.

The type of sitting posture also plays a role in reducing excessive stresses on

the spine, which may lead to LBP (18). Sitting with the back slouched for as little as

20 minutes can result in increased laxity of the posterior spinal ligaments (22).

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4. Constrained Posture

Results show that there is a significant relationship between LBP and

constrained posture.

Posture is the relative arrangement of body parts for a specific activity (1).

Thus, it is important to know and maintain proper posture to avoid stresses which

may cause pain and discomfort. Poor working posture or constrained posture

requires muscles to work at a level near or at their maximum capacity (31). As a

result, there is de-conditioning of the muscles and the entire back becomes sore and

tired, causing low back pain (28).

5. Rough Roads

Rough roads, i.e. rough roads driven and rough road complaints, were found

to be not significantly associated with low back pain.

This is not consistent with the fact that rough roads may result in whole-body

vibration, which occurs while riding vehicles over rough terrain. A related study also

observed a strong correlation between whole body vibration and motor vehicle

driving (44). This may be due to the fact that the bus drivers gave only an estimate

of rough roads experienced while driving.

6. Boredom

Results show that a significant relationship exists between boredom and low

back pain.

Psychological factors are even more important in people with low back pain.

Dissatisfaction with a work situation, a supervisor, or a dead end job and boredom

contribute greatly to the onset and persistence of low back pain (56). Other factors

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which increase the risk of low back pain together with boredom include degree of

focus on the pain, beliefs about the meaning of the pain and a sense of poor control

over the pain (55). In this study, about 66% of the bus drivers who experience

boredom at work have low back pain.

7. Depression

There is a significant relationship between depression and low back pain.

Recent research indicates that in many people, preexisting depression and

the inability to cope may be more likely to predict the onset of pain than physical

abnormalities. People who are depressed are more likely to have vague physical

symptoms, including low back pain. Depression, low activity or high pain behavior,

negative beliefs or fear of pain are the three psychological-behavioral factors that

have continued to show consistent, empirically supported predictive capabilities.

However, it has not been determined which of these factors are greatly involved in

predicting disabling low back pain (53).

8. Frequent Movement of Back

A significant relationship was observed between frequent movement of back

and low back pain.

About 64% of the subjects with low back pain move their backs frequently.

The exact cause of low back pain may be hard to find. Pain can come from muscles,

ligaments, nerves, discs, or bones. People who are inactive are especially at risk of

LBP, are not conditioned, and prone to strains when they move their back frequently.

Repetitive motion injury (RMI), also known as repetitive stress injuries, is a type of

stress injury that results from repetitive motions such as frequent bending or

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sustained awkward positioning performed over extended periods of time without

allowing for sufficient rest (31).

9. Frequent Movement of Shoulders

Results show that frequent movement of shoulders is significantly associated

with low back pain.

Repetitive manipulation of body parts particularly the shoulders while driving

may result in injury or illness of its soft tissues, thus contributing to the development

of low back pain (31).

10. Long Driving Time

Results show that long driving time was significantly associated with low back

pain.

This finding is consistent with a study which showed that driving for eight

hours or more may not protect drivers from harmful vibration exposure leading to low

back pain (51). A related publication also showed that drivers have an elevated risk

for injury that can be attributed solely to their physical working conditions, particularly

the number of hours on the job (42).

11. Long Distance Driving

Results show that long distance driving is significantly associated with low

back pain.

A little over 40% of the subjects drove at a range of 400 to 499 km every day.

Findings from a related study showed that people who drove long distances were at

significantly increased risk of having neck and low back pain. A recent Swedish

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study found significantly increased risks of low back pain among those who drove

long distances and spent a long time each day in their car (41).

12. Vibration Exposure

No significant association was observed between vibration exposure and low

back pain.

Vibration exposure included whole-body vibration and at least 20% rough

roads experienced by the drivers while driving.

This finding is contrary to previous studies conducted on the subject matter

(48, 49, 50, 51). There was sufficient evidence that vibration exposure to drivers

could be a health hazard particularly with regard to back problems. The relatively

high vibration exposure levels combined with long exposure duration and prolonged

sitting are likely to contribute to low back pain. From a study on the association of

whole body vibration and low back pain, it was found that the average WBV level

experienced by drivers of heavy transport vehicles exceeded health, fatigue and

comfort limits of the Australian Standard and most exposures were within the

Caution zone for health according to the current International Standard on whole

body vibration (49). A possible explanation to the negative finding in our study is

that vibration was assessed qualitatively.

13. Employee Satisfaction with Management

Results show that employee satisfaction with the company management is

not significantly associated with low back pain.

This finding is contradictory to previous studies which state that employer

policies, attitudes, and actions determine the satisfaction level of employees, which

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in turn, affects health-related conditions. Social and psychological factors play a role

in how severely someone experiences pain and even vague symptoms. People who

are depressed are more likely to have vague physical symptoms, including low back

pain (53). A related article stated that after accounting for physical work load, a

stressful job with high physiological demands, low satisfaction, and low supervisor

support can cause spinal injury, particularly low back pain (42).

A possible explanation to the negative finding in our study is that information

bias may have occurred. Drivers may not have answered honestly for fear of

dismissal from the company despite assurances of confidentiality.

14. Height

No significant association exists between height and low back pain.

This finding is contrary to previous studies which showed that height is a risk

factor to low back pain. Tall people are at a higher risk of having low back pain than

short people (15). A possible explanation to this finding is that the average Filipino

male height is between 162 and 164 cm (16).

9.3 Multivariate Analysis

The Statistical Package for the Social Sciences (SPSS) version 10 was used

to perform logistic regression. The relationship of risk factors with low back pain was

determined while controlling for the effects of confounders and other independent

variables. The risk factors included age, rough roads experienced, percent of rough

roads, abnormal vibration, vibration exposure, uncomfortable sitting posture,

constrained posture, boredom, depression, frequent movement of back, frequent

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movement of shoulders, long distance driving, long driving time, height, employee

satisfaction with management and insufficient work space. The confidence level

used was 95% with an α equal to 0.05.

Using the backward Wald method, the independent variables were analyzed.

The study claims that the independent variables from the bivariate analysis would

increase the probability that a driver will develop low back pain. A step-by-step

elimination using the backward-Wald method is shown in Appendix A (Table 42-A

and 42-B).

A. Results

Results showed that three independent variables significantly contribute to

the probability of LBP occurrence among bus drivers. These are constrained

posture, employee satisfaction with management and long distance driving.

Table 40. Risk Factors to Low Back Pain

Variable Odds Ratio and Confidence Interval Constrained Posture 3.013 (1.961,4.880)

Long Distance Driving 2.185 (1.111, 4.299) Employee Satisfaction to Management 1.989 (1.153,3.429)

B. Discussion

1. Constrained Posture

Drivers who experience constrained posture while driving have 3 times

greater risk of having low back pain compared to those who do not.

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De-conditioning, which is the weakening of the muscles supporting the

spine and trunk, occurs due to poor working posture or constrained posture. The

former can cause the entire back to become sore and tired, leading to low back

pain.

2. Long Distance Driving

Drivers who drove for at least 300 km per day have 2.1 times higher risk of

developing low back pain than those who drive for less than 300 km in a day.

According to a study, increased risk of having neck and low back pain was

found among those who drive long distances.

3. Employee Satisfaction with Management

Drivers who experienced dissatisfaction with the management are 2.1

times more at risk of having low back pain than those who are satisfied.

Vague symptoms, including low back pain, are more likely to occur among

depressed individuals. A related article stated that after accounting for physical

workload, a stressful job with high physiological demands, low satisfaction, and

low supervisor support can cause spinal injury, which may lead to low back pain.

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10.0 Conclusion

1. Constrained posture is significantly associated with low back pain.

Drivers with constrained posture while driving have 3 times greater odds of

having low back pain.

This finding suggests that maintaining proper posture will reduce the risk of

low back pain.

2. Long distance driving is significantly associated with low back pain.

Drivers who drive for at least 300 km per day have 2.2 times higher risk of

developing low back pain.

This finding suggests that management should look into the possibility of

modifying work shifts of bus drivers based on a 300 km-maximum distance per

day. Hence, this should not generally affect income of drivers on one hand and

company productivity on the other hand.

3. Employee satisfaction with management is significantly associated with low

back pain.

Drivers who show dissatisfaction to management are 2.1 at risk of having low

back pain.

This finding emphasizes the importance of good management-worker

relationship in improving the drivers’ well being. Thus, better work performance,

less absenteeism and increased productivity will be achieved.

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11.0 Recommendations

1. Health education should be conducted in order to inform the drivers about the

effects of long driving time and low back pain.

The causes of low back pain will be discussed. Posters, fliers and multi-

media showing the latest concepts and preventive measures on low back pain

should be provided. Measures to alleviate and prevent LBP can then be made.

2. Regular medical check-ups should be provided by the company to identify and

address health problems of bus drivers, particularly low back pain.

Low back pain which lasts for less than 6 months is acute. However, it is

considered chronic if it occurs for more than 6 months. Early detection of low

back pain in its acute stage is crucial in the prevention of its progression to

chronicity. Therapy for identified low back pain cases is helpful in improving

worker performance.

At present, no health professionals in companies with 300 or more employees

were observed. As a possible solution, bus companies proximate to each other

may employ a part-time health professional which will provide service to the

cluster of bus companies.

3. The company should provide health fitness training for their employees.

Exercise is important in preventing repeat episodes of low back pain

and avoiding it in the first place. The bus company is recommended to have a

resident physical therapist when teaching its employees on how to exercise

safely. A complete exercise program should include aerobic activity as well as

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stretching and strength training. Aerobic exercise has been reported to improve

or prevent low back pain.

Exercises such as abdominal bracing, neutral spine and basic and

advanced curl ups, side bridge and bird dog exercise are recommended by Joy

M. Beatty, MSPT in order to prevent occurrence of low back pain. (See

Appendix B for detailed exercise descriptions.)

4. The companies should have regular maintenance of their buses.

Previous studies have found that bus engines and seats kept in good

condition reduce whole body vibration exposure due to rough roads and poorly

maintained engines. Also, adjustable seats should be maintained in order to

assure sufficient workspace and comfortable sitting posture of the bus driver.

5. Regular meetings should be conducted by the management in order to assess

the working condition of their employees and immediately address problems.

It has been proven that dissatisfaction with a work condition, a

supervisor and boredom can greatly contribute to the onset and persistence of

low back pain. It is therefore important to address these problems in order to

assure worker satisfaction to management.

6. Drivers with special needs, e.g. older employees, those with serious health

complaints and those recovering from an illness should be given some degree of

flexibility in their work schedule. However, individual adjustments in schedule

should not affect the performance of the whole workforce. Recent research

shows that in many people, pre-existing depression and inability to cope may be

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more likely to predict the onset of pain than physical abnormalities. As a result,

there is a significantly higher absentee rate in spite of less stress in their backs.

7. Bus companies should include health programs to be carried out by medical

professionals such as stress management, lecture/demonstration on proper

driving posture and stretching exercises.

8. Bus companies should consider developing a working schedule that would allow

driving shifts every 300 km. This would minimize the risk of having low back

pain. If driving is extended, drivers should be given enough rest periods of at

least 30 minutes.

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13.0 Acknowledgements We would like to express our deepest gratitude and appreciation to the following individuals without whose contribution we could not have completed this research: Dr. Benjamin C. Vitasa, our beloved adviser, for the “lessons learned” which have taught us to go deep into the heart of our research and for bringing out the best in each of us. Dr. Ethel M. Estanislao, our statistics adviser, whose knowledge has enlightened our path towards the fulfillment of our research. Prof. Jingky Lozano, for so graciously sharing her precious time and giving us advice when we needed it most. Prof. Rosebelle Azcuna, for lifting up our spirits with her insights during moments of confusion. Rowena Yra, Shelly La Rosa and Ricky Hipolito, the fun-loving and ever-dependable research assistants, who have supported us through thick and thin. The management of the bus companies for their cooperation in the conduct of our study: Mr. Jun Belen, station master, Tritran Bus Co. Mr. Ruben Locegro, dispatcher, BBL Trans System Mr. Armando Mendoza, station master, Victory Liner Mr. Ricardo Mercado, Jr., traffic operation staff, Grand Star Bus Co. Ms. Jennifer Bañaga, vice president, administration, Philtranco Ms. Pepita Iraya, inspector, JAC Liner, Inc. Ms. Lucita Limosnero, special trip coordinator, Green Star Bus Co. Ms. Josephine Solomon, head, personnel dept, Pangasinan Five Star The three hundred seventy eight bus drivers who participated in this study, for their time and cooperation. Classmates and friends, especially Emmanuel Paragas, Jr., Joseph Eufemio Martinez and Dennis Pascual for their help and encouragement which has taught us to move on. Mrs. Felicidad Serafico and Jollibee for providing food which gave strength to both our minds and bodies. The CPH guards for giving us help and protection whenever we need one. The song “Maybe” for serving as our inspiration and relaxation in the middle of difficulties. Our parents who has shown much love through their unfailing support and understanding: Mr. Teodoro P. Culla and Mrs. Lourdes M. Culla Mr. Edmar O. Martinez and Mrs. Maura S. Martinez Mr. Joselito S. Santiago and Mrs. Precy R. Santiago Mr. Leroy J. Tad-y and Mrs. Josie M. Tad-y And above all, God Almighty, our light and our protection amidst the challenges of life.

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