In a cohort study, the Relative Risk (RR) of lung cancer in smokers versus non-smokers is 15. If the prevalence of smoking in the population is 30%, the Population Attributable Risk Percent (PAR%) is:
- A 82% ✓
- B 14%
- C 55%
- D 93%
Correct answer: A. 82%
Explanation
PAR% = [Pe(RR-1)] / [1 + Pe(RR-1)] × 100, where Pe = prevalence of exposure = 0.30, RR = 15. Numerator: 0.30 × (15-1) = 0.30 × 14 = 4.2. Denominator: 1 + 4.2 = 5.2. PAR% = 4.2/5.2 × 100 = 80.8% ≈ 81–82%. This means approximately 82% of lung cancer in the total population is attributable to smoking and could theoretically be prevented if smoking were eliminated.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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