A cohort study follows 500 smokers and 500 non-smokers for 10 years. During follow-up, 50 smokers and 10 non-smokers develop COPD. What is the Relative Risk (RR) of COPD in smokers compared to non-smokers?
- A 2.5
- B 5.0 ✓
- C 10.0
- D 4.0
Correct answer: B. 5.0
Explanation
Risk in smokers = 50/500 = 0.10; Risk in non-smokers = 10/500 = 0.02. RR = 0.10 / 0.02 = 5.0. This means smokers have 5 times the risk of developing COPD compared to non-smokers. Relative Risk is calculated in cohort studies where incidence in exposed and unexposed can be directly measured. Odds Ratio (used in case-control studies) would approximate RR for rare diseases.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.