A researcher conducts a prospective cohort study and finds Relative Risk (RR) = 0.6 with 95% CI (0.4–0.9) for a dietary intervention on cardiovascular disease. Which statement best interprets this finding?
- A The intervention increases CVD risk by 40%
- B The intervention reduces CVD risk by 40% and the result is statistically significant ✓
- C The result is not statistically significant because the CI includes values below 1
- D The Attributable Risk cannot be calculated from this data
Correct answer: B. The intervention reduces CVD risk by 40% and the result is statistically significant
Explanation
RR = 0.6 means the exposed group has 60% the risk of unexposed, i.e. a 40% reduction in risk. Statistical significance is determined by whether the CI crosses 1.0; here the CI (0.4–0.9) does not include 1.0, so the result IS statistically significant. Option C is incorrect because values below 1 indicate protective effect, not insignificance — significance requires the CI not to span 1.0.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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