A cohort study of factory workers reveals 50 new cases of occupational lung disease over 5 years of follow-up among 1000 person-years of observation. The incidence rate is:

• A 5 per 100 person-years
• B 50 per 1000 person-years ✓
• C 10 per 100 person-years
• D 25 per 1000 person-years

Explanation

Incidence rate = (Number of new cases / Total person-years of observation) = 50/1000 = 0.05 = 50 per 1000 person-years. Person-time denominators account for variable follow-up durations, making the incidence rate more precise than cumulative incidence when follow-up time differs across individuals.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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