A cohort study follows 2,000 smokers and 2,000 non-smokers for 10 years. At the end, 80 smokers and 20 non-smokers develop lung cancer. The Attributable Risk Percent (ARP) in smokers is:
- A 60%
- B 75% ✓
- C 80%
- D 85%
Correct answer: B. 75%
Explanation
Incidence in smokers = 80/2000 = 0.04; incidence in non-smokers = 20/2000 = 0.01. Attributable Risk (AR) = 0.04 - 0.01 = 0.03. ARP = (AR / Incidence in exposed) × 100 = (0.03/0.04) × 100 = 75%. ARP indicates what proportion of the disease burden in exposed individuals is due to the exposure and would be eliminated by removing it.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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