Occupational_Epidemiology NIOSH for OH Doctors

Occupational Health

1. OCCUPATIONAL EPIDEMIOLOGY
Workshop on Introductory to Occupational
Health
Copyright@NIOSHEdition 20161

2. Contents
❖Definition
❖Application of epidemiology in occupational
health
❖Data from occupational settings
❖Exposure assessment
❖Outcome measures
❖Use of rates as epidemiological measurements
❖Roles of accident and incident statistics
❖Linking disease with exposure
❖Association and causation
❖Limitations in epidemiology
❖Conclusion
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3. Definitions
EPI+ DEMOS + LOGOS
(among) (the people) (the study)
❖The study of distribution & determinants of
disease in populations
❖how & why disease distributed in group of
people
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4. Application of Epidemiology in
Occupational Health
❖Connection between occupation & disease
–Scrotal cancer among chimney sweeps (Sir Percival Pott 1775)
❖For risk assessment
–Follow-up on survivors of Hiroshima & Nagasaki bombings –risk of
cancer, childhood leukemia
❖Evaluation of substance harmful to human
❖Setting standard of exposure
–e.g. TLV for vinyl chloride was bring down from 500 ppm to 5 ppm due
to increased cases of hepatic angiosarcoma due to vinyl chloride
exposure
❖Health monitoring
–what test; frequency of medical examinations
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5. Application of Epidemiology in
Occupational Health….. cont’d
Concept of work-related disease and injury
❖work is the necessary cause
❖work is a contributory cause
❖work is aggravating an established condition
❖work is offering accessibility to potentially
dangerous substances
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6. Type of Data From
Occupational Settings
1. Data collected for other purposes
(e.g. vital registration data, official employment records etc.)
2. Data collected specifically for the
evaluation of health outcomes of certain
exposures (e.g. accident rate, mesothelioma cases)
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7. Type of Occupational
Measurements
Two most important group of measurements
1.Exposure assessment
2.Outcome measures
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8. Exposure
Measurement
❖Biological measurement
❖Environmental measurement
❖Proxies for exposure data
-work area, type of work, occupational title
-duration of employment
-ever employed
-job exposure matrices
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9. Outcome Measurement
❖Discrete events
1. Medical / health (5D) -death, disease, discomfort,
disability, dissatisfaction
2. Industry –loss workday cases
❖Rate
1. sickness absence rate / accident rate
2. loss time injury rate
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10. What is rates?
❖A measure of frequency of the occurrence of a
phenomenon.
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11. Use of Rates as Epidemiological
Measurement
❖Count of events (accidents or
disease)
e.g. They were 60 road traffic accident among bus
drivers in a town, and 30 road traffic accidents
among taxi drivers in a town last year
What is your conclusion ?
How you get meaningful comparison ?
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12. The Use of Rates As
Epidemiological Measurement
Type of Rate
Rate ( a / b )
❖Numerator ( a ) –total number of events measured
❖Denominator ( b ) –population at risk (all those in
whom the event can happen)
❖Advantage –the event / diseases occurrence in two or
more groups can be compared
❖Two types
1. Prevalence rate
2. Incidence rate
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13. The Use of Rates As Epidemiological
Measurement
Prevalence Versus Incidence
Incidence Prevalence
Numerator New cases All cases (old + new)
Denominator All persons exposed to
risk
All persons at risk
Time Duration of period Single point
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14. The Use of Rates As Epidemiological
Measurement
Comparison
❖Comparison become meaningful when the
denominators are include –duration of exposure /
the working time
❖Accident rate / sickness absence rates are
commonly used to assess hazards, behavioral
characteristics, and the effect of working conditions
(e.g. shift work)
❖Comparison
1. Frequency rate
2. Severity rate
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15. The Use of Rates As Epidemiological
Measurement
Accident Rate
❖The accident frequency rate
Total no. of accidentx 1,000,000
Total no. of man-hours worked
❖Accident severity rate
Total no. of days lostx 1,000,000
Total no. of man-hours worked
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16. NATIONAL OCCUPATIONAL
INCIDENT & FATALITY RATE
Year 2013 2014
Incident (per 1,000
workers)
3.28 3.10
Fatality (per 100,000
workers) 4.62 4.21
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17. Roles of Accident & Incident
Statistics
❖Identification of areas or process for further
investigation
❖Helps to justify expenditure
❖Assists in the setting of future targets
❖Helps to meet statutory reporting requirements of
accidents, occupational diseases and dangerous
occurrences
❖Provides a performance indicators
❖Is useful for educational purposes
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18. Linking disease with
Exposure… cont’d
Calculating measures of effect
Simple risk
Death rate from lung cancer in asbestos worker 0.96/1000/year
Death rate from lung cancer in non asbestos worker0.07/1000/year
Compared risk
Relative risk = 0.96/1000/year 0.07/1000/year = 13.7
Attributable risk= 0.96/1000/year -0.07/1000/year = 0.89/1000/year
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19. Linking Disease With Exposure
❖Measure of effect is RISK
1. Relative risk (RR)
`the ratio of the chance of a disease developing among members of a
population exposed to a factor compared with a similar population not
exposed to the factor.’
2. Attributable risk (AR)
` the amount or proportion of incidence of disease or death (or risk of
disease or death) in individuals exposed to a specific risk factor that
can be attributed to exposure to that factor’
–it measures the rate of disease that can be attributed to the exposure
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20. Criteria for Causation
❖Strength of association
❖Reversibility
❖Consistency
(reproducibility)
❖Specificity
❖Exposure-response
❖Temporality
❖Biological gradient
❖Plausibility
❖Coherence
❖Experiment
❖Analogy
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21. Limitations in epidemiology
1. Poor response rate
2. High turnover of the study population
3. Healthy worker effect
4. Poor quality of exposure measurement data
5. The problems of multiple exposures
6. Poor quality of outcome (health) data
7. Having a study period shorter than the latency
period of the health effect
8. Problems associated with the study of small
populations
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22. Conclusion
❖Occupational Epidemiology is useful to determine
patterns of disease among workers
❖Understanding relevant epidemiologic tools is
important in order to link exposure factors to
occupational diseases
❖Criteria for causation and epidemic limitations must
be considered when determining the cause of
diseases in occupational health settings
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23. Questions
Q1: What is the definition of epidemiology?
Q2: List the parameters of exposure assessment in
occupational epidemiology
Q3: List the parameters of outcome assessment in
occupational epidemiology
Q4 : Explain how epidemiology concept can be applied in a
workplace?
Q5 : Explain how data in accident rate / absent rate can
help you in the workplace?
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