A pharmaceutical company conducts a cohort study to evaluate the effect of a new antiplatelet drug (Drug X) on the risk of ischemic stroke. In the overall study population, Drug X reduces the risk of stroke compared with placebo (relative risk [RR] = 0.70). The investigators then stratify the results by sex and obtain the following RRs:
• Men: RR = 0.40 (95% CI: 0.25–0.64) • Women: RR = 0.88 (95% CI: 0.60–1.30)
Which of the following best describes the role of sex in this study?
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