Epidemiology NCD - Copy

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EPIDEMIOLOGY OF

NONCOMMUNICABLEDISEASES

PLMPLM ± ± FCM2FCM2



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LEARNING OBJECTIVES

1. Differentiate noncommunicable fromcommunicable diseases in terms of the ff:

1.1. Characteristics of the agent

1.2. Time frame between exposureand disease

1.3. Nature of the disease

1.4. Interaction of agents of disease



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2. Explain some important methodologicalissues

2.1. Natural history2.2. Case identification2.3. Measuring exposure2.4. Issues of conflicting findings2.5. Investigation of causal factors

3. Give examples of major categories of etiologic agents of non-communicablediseases

4. Explain the important considerations in theinvestigation of environmental andoccupational exposures



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EPIDEMIOLOGY OF NCD

I. Comparison of communicable and non-communicable diseases

II. Methodological issues in the study of non-communicable diseases

III. Major categories of etiologic agents

IV. Approaches to the control of non-communicable diseases



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Non-Communicable Diseases

Includes all ³traditionally´ defined NCDs

such as CVD, cancer, chronic respiratory

diseases, mental health as well as injuriesand violence

In all WHO regions (except sub-Saharan

Africa), NCDs today constitute the largest

contributor to burden



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Situationer: NCD

rising trends in non-communicable diseases as aresult of demographic and epidemiologicalchanges, as well as economic globalization

increase in life expectancy combined with changesin lifestyles are leading to epidemics of non-communicable diseases (NCD), mainlycardiovascular diseases, cancer and diabetes

In 1998, NCD accounts for 63% of global deaths

43% of all DALY globally were attributed to NCD



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Communicable diseases 17,380

Non-communicable diseases 33,484

Injuries 5,101

Cardiovascular diseases 16,970

Cancers 7,065

Respiratory diseases 3,575

Digestive diseases 2,409

Neuropsychiatric disorders 911Genitourinary diseases 900

Source: Adapted from The World Health Report 2000, WHO

Causes of Death Worldwide: estimates for 1999

(in thousands)



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Communicable diseases 615,105

Non-communicable diseases 621,742

Injuries 201,307Cardiovascular diseases 157,185

Neuropsychiatric disorders 158,721

Cancers 84,500

Respiratory diseases 70,017

Congenital abnormalities 36,557Source: Adapted from The World Hedalth Report

2000, WHO

Burden of Disease Worldwide: Estimates for 1999 (in thousands)

Disability-Adjusted Life Years



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Trend of Leading Causes of Mortality

, 1975 -1995

RANK 1975 1980 1985 1990 1995

1 Pneumonias Pneumonias Pneumonias Heart Diseases Heart Diseases

2 TB, all forms Heart Diseases Heart Diseases Pneumonias Diseases of the

Vascular system

3 Heart Diseases TB, all forms TB, all forms Diseases of the

Vascular System

Pneumonias

4 Diseases of the

Vascular System

Diseases of the

Vascular system

Diseases of the

Vascular System

TB, all forms Malignant

Neoplasm

5 Malignant

Neoplasm

Malignant Neoplasm Malignant

Neoplasm

Malignant

Neoplasm

TB, all forms

6 Gastroenteritis

and colitis

Diarrheas Diarrheas Diarrheas Accidents

7 Avitaminosis and

other nutritional

deficiencies

Accidents Accidents Septicemia Chronic

Obstructive

Pulmonary

Disease

8 Accidents Avitaminosis and

other nutritional

deficiencies

Measles Nephritis,

nephritic

syndrome and

nephrosis

Other diseases of

the respiratory

system

9 Bronchitis Measles Avitaminosis andother nutritional

deficiencies

Accidents Diabetesmellitus

10 Tetanus Nephritis, nephrotic

syndrome and

nephrosis

Nephritis,

nephrotic

syndrome, and

nephrosis

Measles Diarrheal

diseases

Source: Phil. Health Statistics



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MORTALITY

Ten Leading Causes of Mortality by SexNumber, Rate/100,000 Population & Percentage

, 2003

Cause Male FemaleBoth Sexes

Number Rate Percent*

1. Heart Diseases 38,677 29,019 67,696 83.5 17.1

2. Vascular System Diseases 29,054 22,814 51,868 64.0 13.1

3. Malignant Neoplasm 20,634 18,664 39,298 48.5 9.9

4. Accidents 27,720 6,246 33,966 41.9 8.6

5. Pneumonia 15,831 16,224 32,055 39.5 8.1

6. Tuberculosis, all forms 18,367 8,404 26,771 33.0 6.8

7. Symptoms, signs andabnormal clinical, laboratoryfindings, NEC 10,740 10,623 21,363 26.3 5.4

8. Chronic lower respiratorydiseases

12,998 5,907 18,905 23.3 4.8

9. Diabetes Mellitus 6,823 7,373 14,196 17.5 3.6

10. Certain conditionsoriginating in the perinatalperiod 8,397 5,725 14,122 17.4 3.6

Source: The 2003 Philippine Health Statistics

* percent share from total deaths, all causes,



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MORTALITY

Ten Leading Causes of Mortality by Sex

Number, Rate/100,000 Population & Percentage, 2002

Cause Male Female

Both Sexes

Number Rate Percent*

1. Heart Diseases 39,502 30,636 70,138 88.2 17.7

2. Vascular System Diseases 27,536 21,983 49,519 62.3 12.5


4. Pneumonia 16,729 17,489 34,218 43.0 8.6

5. Accidents 27,448 6,169 33,617 42.3 8.5

6. Tuberculosis, all forms 19,293 9,214 28,507 35.9 7.2

7. Chronic obstructive

pulmonary diseases andallied conditions

13,007 6,313 19,320 24.3 4.9

8. Certain conditions

originating in the perinatalperiod

8,520 5,689 14,209 17.9 3.6


10. Nephritis, nephriticsyndrome and nephrosis

5,358 3,834 9,192 11.6 2.3

Source: 2002 Philippine Health Statistics



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MORTALITY

Ten Leading Causes of Mortality by Sex Number, Rate/100,000 Population & Percentage , 2000

Cause Male Female TotalNumber

Rate % of TotalDeaths

1. Diseases of theheart

34,356 26,061 60,417 79.1 16.5

2. Diseases of thevascular system

27,197 21,074 48,271 63.2 13.2


4. Pneumonia 16,549 16,088 32,637 42.7 8.9

5. Accidents 26,009 6,346 32,355 42.4 8.86. Tuberculosis, allforms

18,590 8,967 27,557 36.1 7.5

7. Chronic obstructivepulmonary diseasesand allied conditions

10,770 5,134 15,904 20.8 4.3

8. Certain conditionsoriginating in theperinatal period

9,083 6,015 15,098 19.8 4.1


10. Nephritis, nephriticsyndrome andnephrosis

4,642 3,321 7,963 10.4 2.2



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³epidemiologic transition´

trend in many countries have been impacted

by a new epidemic disease ± HIV/AIDS

Ascendancy of noncommunicable

diseases



Ascendancy of noncommunicable diseases

this leaves many countries with a double

burden of health problems:

a new epidemic of infectious disease and

unresolved infectious conditions

a growing set of noncommunicable diseases.

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Ascendancy of noncommunicable diseases

Epidemiologic transition in the Philippines

Epidemiologic transition varies; reflecting the

social, cultural, economic, and health resource

factors

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NCDs accounted for 60% of all deaths in

1999 and 43% of all DALYs with injuries

adding 9% of all deaths and 14% of all

DALYs

By 2020, 10 out the top 15 causes of

DALYs lost will be attributable to NCDs,

mental health and injuries/violence



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The top five positions will be occupied by

Ischemic Heart Disease, depression, road

traffic injuries, cerebrovascular disease

and Chronic Obstructive Pulmonary

Disease (COPD)

15th place: trachea, bronchus and lung

cancers (better known as tobaccocancers)



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GROUP OF NCDs

Cancers Lifestyle-related (CVD, diabetes)

Injury (unintentional, intentional)

Genetic disorders Disabling disorders

Occupational disorders

Nutritional conditions

Endocrine disorders Substance abuse



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REASONS FOR THEPROMINENCE OF NCD

1. Aging of the population

2. Impact of automobiles

3. Lifestyle changes4. Tobacco addiction

-single largest cause of preventable morbidity

and mortality

5. Physical activity6. Social and behavioral factors



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A. CHARACTERISTICS OF THE AGENTe

± Absence of a single necessary agent

± most NCDs are classified on the basis of manifestations rather than on etiology (e.g.,CVD, renal disease, neoplasms)

± known ³causes´ are risk factors

e.g. obesity, elevated cholesterol levels,hypertension

I. NATURAL HISTORY



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B. TIME FRAME

- take years or decades before illness isapparent

- no multiplication of causative agent isinvolved

- multiple low-dose exposures (somechemicals)

- some conditions seem to evolve

subsequent to chronic conditions orhigh risk states such as obesity,smoking, diabetes and high bloodcholesterol



Disease Induction and Latency

Interval

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³Emperical induction time´ = time since first exposure

Exposure

First exposedCase or Death

Identified

T I M E

Disease induced

Induction Period Latency Period



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C. NATURE OF THE DISEASE

±chronic in nature

± ³chronic disease´

(1957 Commission on Chronic Disease)

»permanent

»leaves residual disability»caused by nonreversible pathological

alterations

»requires special training of the patient

for rehabilitation»requires long periods of supervision,

observation or care.



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±Chronicity

function of the long latency period

slow disease process p adaptiveresponses to stresses (may bedetrimental over the long term)

CD can be chronic (e.g. rheumaticheart disease)

NCD can be acute (e.g. chemicalpoisoning)



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D. Synergism in Disease Causation

> Asbestos and lung cancer (RR=8)

> Smoking + asbestos and lungcancer (RR=90)

- Presence of synergism p decreasedlatency (produce illness in the prime of life even with low level exposures)

- Role of initiators and promoters



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SUMMARY OF DIFFERENCES:

INFECTIOUS DISEASE NON-INFECTIOUS DISEASE

Single necessary agent No single necessary agent

Agent-disease specificity Seldom agent-disease specificity

Causes are known Causes are unknown

Intervention often based on risk

factors

Short incubation period Long latency period

Single exposure usually

sufficient

May require multiple exposure to

same or multiple agents

Usually produce acute disease Most often produce chronicdisease

Acquired immunity possible Acquired immunity unlikely

Diagnosis based on tests

specific to disease agent

Diagnosis often dependent on

non-specific symptoms or tests



Methodological Issues in the Study of NCD

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³Emperical induction time´ = time since first exposure

Exposure

First exposedCase or Death

Identified

T I M E

Disease induced

Induction Period Latency Period



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II. Methodological Issues in theStudy of NCD

A. Natural history

- lack of a single necessary agent causing thedisease makes it more difficult to isolate the effect

of any individual factor

- synergistic effects of other agents and effects of known causes must be controlled

- long latency period precall problems

- chronic nature and low frequency of occurrence pprevalent cases studied rather than incident casesp difficult interpretation of causality



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B. CASE IDENTIFICATION

- presence or absence of a cluster of

symptoms- criteria for diagnosis may vary byinstitution or by physician p researchusing medical records problematic

C. MEASURING EXPOSURE

- quantification is important butproblematic

- acuteness or chronicity/high dose orlow dose



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- Is dose a function of a metabolite, enzymaticalteration, level of the original agent?

- environmental levels or body levels?

- plasma levels, brain concentration, kidney, or someother organ tissue?

- Precise quantification identifies levels hazardous tohealth p important for planning control measures.

- Demonstration of dose effect helps establish causalrole for the agent

- Constancy or intermittence of the exposure

- relevant time or period of exposure



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D. CONFLICTING FINDINGS ANDCAUSALITY

- publication bias

- criteria for causality:

strength of association

temporal correctness

dose-effect relationship

biological plausibilityconsistency of findings

specificity of relationships



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Problems in investigating diseaseProblems in investigating disease

etiologyetiology

1. Absence of a known agent

± especially a problem for chronic diseases;

± makes diagnosis difficult;

± absence of good tests may make distinction

between diseased and non-diseased persons

very difficult;



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etiology (con¶t.)etiology (con¶t.)

2. Difficulty of measuring and characterizing

exposure

± Quite problematic in environmentalexposures;

± Technology to accurately detect/measure

exposures may not be available;



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3. Multi-factorial nature of etiology

± Relevant factors may be both environmental

and constitutional;

± Relevant factors may also interact with other

factors;



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4. Long latent period

± Presence of a long latent period during which

host and environmental factors interact beforethe disease becomes manifest;

± The long latent period makes it difficult to link

antecedent events with the outcomes;



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5. Indefinite onset

± Most chronic diseases, for example, are

characterized by indefinite onset;

± The problem of identifying the time of onset of

the disease makes collection of incidence

data difficult;



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6. Differential effect of factors on incidence and

course of disease

the nature of the exposure-diseaserelationship may be different during the initial

development of the disease and the later

course of the disease (i.e., factors may act

differently at various stages of the disease



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example ± cancer of the breast and SES

Incidence of breast cancer is generally higher

among women with high SES than women with low

SES;Studies from the California Tumor Registry have

shown that, within stage, survival of patients with

breast cancer was better for more advantaged

women (e.g., those treated in private rather thancountry hospitals). Lower incidence among low

SES but better prognosis among those with high

SES.



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Major Categories of

Etiological Agents

A. Occupational

B. General environmental

C. Lifestyle and Illness



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OCCUPATIONAL

- chemical- metals and naturally occurring minerals



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Investigating occupational exposures

agent factors to be considered

±size and shape of particles

±route of exposure

±free or compound form

±organic vs inorganic form

±liquid or vapor form



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environmental factors±conditions in the work environmental

that will influence the likelihood thatworkers will come in contact with anagent

±general cleanliness and ventilation

±lighting, temperature

Host factors±lifestyle behaviors that may increase

the risk of disease from occupationalexposure to an agent

±genetic constitution



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ENVIRONMENTAL

sources of exposure

±contamination of air, water and soil byindustrial activities or inadequate waste

disposal± lower dose of exposure than inoccupational environments

pesticides

housing materialsautomobile exhausts

radiation



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Investigating environmental exposures

±dose±data on levels of exposure

±mobility of subjects

±confounders

additional considerations

±wide range of ages

± length of exposure

±meterological conditions

±seasonal effects



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LIFESTYLE

- poverty, stress, exercise, drug and alcohol

use, nutrition



OUTCOME MEASURES: (HEALTH

STATUS)

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-MORTALITY RATE

-MORBIDITY RATE

-DALY



Disability Adjusted Life Year (DALY)

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Health gap measure that extends the concept

of potential years of life lost due to prematuredeath (PYLL) to include equivalent years of

³healthy´ life lost by virtue of being in states

of poor health or disability.



Disability Adjusted Life Year (DALY)

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Calculated as the sum of the years of life lost due topremature mortality (YLL) in the population and the

years lost due to disability (YLD)

DALY = YLL + YLD

YLL = N x L

WHERE: N ± number of deaths

L ± standard life expectancy at age of

death in yrs

Y L D = I x D W x LWhere: I ± number of incident cases

DW ± disability weight

L ± average duration of the case until remission or

Death (years)



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CONTROL OF NCD

A. PRIMARY PREVENTION

- removal of agent from environmental orminimizing the amount of agent present

- Protection of the susceptible host from

exposure

B. SECONDARY PREVENTION

- screening tests

C. TERTIARY PREVENTION

- lifestyle modification



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A small core of risk factors explains the increases inCVD, certain cancers and their closely linkedconditions of obesity, type II diabetes:

± tobacco, diet/nutrition, physical inactivity andalcohol

A substantial proportion of chronic respiratorydiseases and death are driven by tobacco use

Alcohol is obviously a major contributor to all causesof injuries and violence



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Tobacco trends are not hopefulTobacco trends are not hopeful

There are 1.2 billion smokers in the worldwith smoking rates in 13 to 15 year olds

being about 20% in diverse cities from

developed and developing countries Tobacco causes 4 million deaths per year,

a figure that will increase to 10 million per

year by the late 2020s The public health impact is widespread and

increasing fast in developing countries



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Trends in alcohol use:

± steady increases in many developing

countries with continued very high rates of

binge drinking in many east and centralEuropean countries.

Alcohol Use



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Obesity

has tripled in youth in several Chinese cities,and rapidly increased over the last 15 years inthe major cities of countries like Malaysia,Brazil, Indonesia and South Africa

But these have occurred as underweightpersists in the rural areas

Often underweight is common in the sameneighborhoods as obesity is increasing

Thus both being underweight and beingoverweight are associated with poverty



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Epidemics of obesity and type II diabeteshave been well documented in mostPacific Island States and are probablyfuelled by a combination of factors:

± increased imports of high fat foodsparticularly cheap off-cuts as well asincreased consumption of sodas in societieswhere physical activity levels haveplummeted.

Devastating economic impact of diabetes¶ complications are recentlybeing determined for several of these

countries

Obesity (con¶t)



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The problems of obesity and diabetes

are caused by many factors

Solutions similarly need to be

multidimensional and avoid focusing on

just one aspect or on behavior change

alone



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Mental health:

± 450 million people who suffer frommental or neurological disorders or

from psychosocial problems such as

those related to alcohol and drug abuse

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