The risks of shift and extended work hours

Laurence Hartley

Murdoch University

This talk

• First half presents the hazards of shiftwork

• Second half presents the hazards of extended work hours

What is shift work?

• Shift work: the alternation of teams of workers, usually performing the same tasks, so work can continue for longer than one work period

• Some or all, work will occur outside of daytime hours

• Work hours can be fixed or rotate (change) and rotation can be fast or slow

What’s the problem for shiftworkers? The rhythms of alertness & sleepiness

The daily circadian rhythms• Rhythms driven by clock in brain• Alertness is max during the day• Sleepiness increases during the night• Maximum sleepiness in pre-dawn• Clock is mainly set by day light• So clock time cannot be easily changed• So workers do not adapt much to

shiftwork

The 4 Hazards of Shiftwork 1. Increased risk of errors & accidents

when working or driving at night 2 Insufficient daytime sleep leads to increased fatigue & sleepiness

3. Increase in health problems

4. Increase in social and domestic problems

1. Daytime sleep is insufficient for night

shiftworkers

alertness &daytime sleep

• Circadian rhythms (daily rhythms) in body clock keeps body awake and alert during the day; daytime not suitable for sleep!

• Circadian rhythm of alertness means night workers are most sleepy at work and driving home

shiftwork sleep problems

• Other ‘disturbances’ during the day eg. noise, light, heat

• Body rhythms and external disturbances combine so that day sleep is shorter (1-2hrs) and of poorer quality than night sleep

• Early shift start times cut down night sleep

sleep loss & shiftwork• Insufficient sleep (<7-8hrs) or poor quality sleep

leads to sleepiness & fatigue, and decreased alertness & performance

• A “sleep debt” of ~ 2 h per night shift accumulates; 3 night shifts = 1 lost sleep.

• 2-3 nights needed to recover from debt.

• Workers may not realise how sleepy they are at work (masking) till driving home

Sleep loss leads to microsleeps

• Insufficient sleep increases the likelihood of “microsleeps” and ‘nodding off’ occurring

• People are unaware of microsleeps

• Loss of awareness and control of surroundings ……. an accident can happen!

2. More errors and accidents at night

Folkard (2003) Mean relative risk across 3 shifts

SHIFT

Night (22-06)Afternoon (14-22)Morning (06-14)

Me

an

RR

1.4

1.3

1.2

1.1

1.0

.9

Folkard (2003) Mean relative risk over 4 successive night shifts

Successive Night Shifts

4321

Me

an

RR

1.5

1.4

1.3

1.2

1.1

1.0

.9

Folkard (2003) Relative risk of different blocks of successive night shifts

No of Successive Nights

7654321

Me

an

RR

1.5

1.4

1.3

1.2

1.1

1.0

.9

driving• Three times risk of a crash with less 6 h sleep

• Night workers are more likely to fall asleep at the wheel, and to have a crash or near-miss than day workers

• Night workers are at 6 times the risk of a car crash than day workers, especially at dawn

• Fatigue and shift work is a major workplace road safety issue

staying awake and BAC• Long hours awake without sleep can

impair performance to a similar/greater level than acceptable BAC for driving

17hrs awake leads to performance similar to BAC 0.05%

20-25hrs awake leads to performance similar to BAC 0.1%

3. More health problems on the night shift

adverse health concerns• Gastrointestinal complaints

- 20-75% night shift workers - 10-20% day & evening workers

• Cardiovascular Disease - a 40% increased risk for developing

cardiovascular disease for shift workers

4. Social and Domestic Problems for the night

shift

family and friends

• Shift workers can have less ‘suitable’ time off and less ‘quality’ time off

• Shift workers often curtail their sleep time to be with family and friends; this means they can be awake for a long period of time, and they do not get enough sleep

Risks of extended hours of work

Folkard (2003) Relative risk over hours on duty

Hours on Shift

121110987654321

Me

an

RR

2.5

2.0

1.5

1.0

.5

0.0

Folkard (2003) Estimated relative risk on different lengths of shift

Length of Shift (hours)

121110987654321

Me

an

RR

1.3

1.2

1.1

1.0

.9

.8

.7

.6

.5

.4

Folkard (2003) Estimated relative risk on different spans of 8, 12 h

No of Successive Nights

7654321

Me

an

RR

1.8

1.6

1.4

1.2

1.0

.8

8-hour

12-hour

Hours of work-relative transport crash risk. Folkard, (1997)

Hours of work -U.S. F.M.C.S.A.

Shift work hazard control strategies

Three Essential Shift Work Hazard Control Measures

1. Adequate, good quality sleep

2. Suitable shift work schedules

3. Appropriate work conditions

1. Adequate, good quality sleep

sleep hygiene rules

• Maintain pre-sleep routines similar to night sleep

• Bedroom dark and quiet

• Avoid caffeine for 5 hrs before sleep

• Avoid alcohol before sleep

• Avoid exercise before sleep

napping• Naps can help maintain alertness,

performance, and safety

• Naps can supplement insufficient sleep,

but …

• BEST if taken after 7-8hrs main sleep and before feeling fatigued:Nap at home before night shift Nap early in the night shift Nap before driving home after night shift

2. Suitable shift work schedules

shift work schedules• No “one best” shift work system

• Employers should consider their worker population and work tasks, and decide, in collaboration with workers, on the most suitable schedule for their work place

• Then evaluate the schedule

Recommendations• Rapid rotations are preferred to slow rotations

• No more than 2 consecutive night shifts

• Forward (clockwise) rotation of shifts

• 8hr shift length; 12hrs maximum

• 5-7 consecutive work days maximum Fewer if shifts >8hrs or night shifts

recommendations

• 2 days off minimum after a block of shifts More if shifts >8hrs or night shifts

• 11hrs off minimum between

consecutive shifts

• Keep schedules regular and predictable, but allow flexibility

3. Appropriate work conditions

rest breaks

• Regular rest breaks reduce accidents

• Incorporate movement, stretching or light exercise, social interaction

• A proper meal break away from work duties

work schedule

• Employers should tailor work tasks according to shift time; some tasks are not suitable for night shift

• Work tasks should vary during the shift

• Schedule tasks so monotonous, boring, dangerous, and safety critical tasks are done early in the night shift

work environment

• Bright lighting, comfortable temperature, and good ventilation

• Background music may help temporarily

• Appropriate facilities for healthy eating

• Napping facilities

Summary

• Shift work is an OH&S hazard – employers and employees have a duty of care to control or minimise the hazards

• Mutual responsibility is essential

• Employers – duty of care to provide an appropriate work schedule and work environment, and continuing education and training for workers about coping strategies

• Employees – duty of care to follow the recommended strategies to manage their sleep, health, and family life