In a prospective cohort study on alcohol and oesophageal cancer, 1200 exposed (heavy drinkers) and 3600 unexposed individuals are followed for 10 years. 48 exposed and 36 unexposed develop oesophageal cancer. The attributable risk percent (AR%) in the exposed is closest to:
- A 25%
- B 75% ✓
- C 50%
- D 67%
Correct answer: B. 75%
Explanation
Incidence in exposed = 48/1200 = 0.04; incidence in unexposed = 36/3600 = 0.01. Attributable risk = 0.04 − 0.01 = 0.03. AR% = (0.03/0.04) × 100 = 75%. This means 75% of oesophageal cancer cases among heavy drinkers are attributable to alcohol. Options A, B and C reflect incorrect computation of the ratio.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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