In a case-control study, OR for smoking and lung cancer is 4; 30% of controls smoked. The Population Attributable Risk Percent (PAR%) using the Levin formula is approximately:

• A 30%
• B 53%
• C 75%
• D 47% ✓

Explanation

Levin's PAR% = [Pe(RR–1)] / [1 + Pe(RR–1)] × 100, where Pe = exposure prevalence in the population (~controls) = 0.30, RR ≈ OR = 4. PAR% = [0.30 × 3] / [1 + 0.90] × 100 = 0.90/1.90 × 100 ≈ 47%. PAR% estimates the proportion of lung cancer in the entire population attributable to smoking; eliminating smoking would theoretically reduce the population lung cancer incidence by ~47%. It integrates both effect size (OR) and exposure frequency.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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