Relative and Atribute Risk
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This document discusses different risk measures used in epidemiology, including relative risk, odds ratio, and attributable risk. Relative risk measures the strength of association between an exposure and disease based on prospective studies. Odds ratio is used similarly in case-control studies when relative risk cannot be directly calculated. Attributable risk determines how much disease can be attributed to a specific exposure by comparing disease rates in exposed and unexposed groups. These measures provide important information for evaluating disease causation and determining potential disease prevention through reducing exposures.
Relative and Atribute Risk
- 1. Relative and Attributable Risks BY DR MUHAMMAD TAUSEEF JAVED CONSULTANT MINISTRY OF HEALTH MAKKAH KSA & IPH LAHORE
- 2. Absolute Risk • Involves people who contract disease due to an exposure • Doesn’t consider those who are sick but haven’t been exposed
- 4. Relative Risk Definition: A measure of the strength of association based on prospective studies (cohort studies).
- 8. Relative Risk Calculations (cont.)
- 9. Relative Risk in Case-Control Studies • Can’t derive incidence from case- control studies Begin with diseased people (cases) and non-diseased people (controls) • Therefore, can’t calculate relative risk directly • But, we can use another method called an odds ratio
- 10. Odds Ratio in Prospective (Cohort) Studies
- 11. Odds Ratio in Case-Control Studies
- 12. Odds Ratio in Case-Control Studies (cont.)
- 13. When is the Odds Ratio a Good Estimate of Relative Risk? • When cases are representative of diseased population • When controls are representative of population without disease • When the disease being studied occurs at low frequency
- 14. REMEMBER !!! • An odds ratio is a useful measure of association • In a cohort study, the relative risk can be calculated directly • In a case-control study the relative risk cannot be calculated directly, so an odds ratio is used instead
- 15. Attributable Risk Definition: The amount of disease that can be attributed to a certain exposure.
- 16. Concept of Attributable Risk
- 17. Attributable Risk for an Exposed Group
- 18. OR, expressed as a proportion: Attributable Risk for an Exposed Group (cont.) From previous relative risk example:
- 19. Calculation for Proportional Incidence in Total Population First calculate A-R for group from Formulas 11.1 & 11.2 (previous slide), then use Formula 11.3 For proportion of the incidence in the total population, use Formula 11.4
- 20. Calculations for Attributable Risks (cont.)
- 21. Summary • Relative risk and odds ratio are important as measures of the strength of association Important for deriving causal inference • Attributable risk is a measure of how much disease risk is attributed to a certain exposure Useful in determining how much disease can be prevented • Therefore: Relative risk is valuable in etiologic studies of disease Attributable risk is useful for Public Health guidelines and planning