Attributable risk and population attributable risk

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2. RISK FACTOR
An attribute or exposure that is significantly
associated with the development of a disease
Epidemiological methods (case control ,cohort
study) gives clue to identify risk factors and to
estimate degree of risk

3. Estimation of risk
Relative risk = Ie / Ine
Ie –incidence of disease among exposed
Ine –incidence of disease among nonexposed

4. Attributable risk
It indicates to what extent the disease under study can be
attributed to the exposure
attributable risk=Risk difference

5. Difference in incidence rates of disease (death) between an
exposed group and nonexposed group
Often expressed as percentage
ATTRIBUTABLE RISK = incidence of disease rate among
exposed-incidence of disease rate among non
exposed/incidence rate among exposd x 100

6. Incidence rate yes =10 per 1000
no =1 per 1000
relative risk = 10/1 = 10
Attributable risk = 10-1/10 x 100 = 90%
drunken Developed
accident
Did not develop
accident
Total
Yes 70 6930 7000
no 3 2997 3000

7. Incidence rate yes = 8 per 1000
no = 2 per 1000
relative risk = 8/2 = 4
Attributable risk = 8-2/8 x 100 = 75%
Over speed
( > 75km\hr)
Developed accidentDid not develop
accident
Total
Yes 80 9920 10000
no 10 4990 5000

8. POPULATION ATTRIBUTABLE RISK
•Reduction in incidence that would be observed if the
population were entirely unexposed compared with the
current exposure pattern
•It is the incidence of the disease /death n the total population
minus the incidence of disease / death among those who were
not exposed to the suspected causal factor

9. Relative risk vs Attributable risk
Drunken
relative risk = 10/1 = 10
Attributable risk = 10-1/10 x 100 = 90%
Overspeed
relative risk = 8/2 = 4
Attributable risk = 8-2/8 x 100 = 75%

10. It gives a better idea on the impact of successful preventive /
public health programme might have in reducing the problem

Guide policy makers in planning public health interventions