BMJ 统计问题（8）：关于疾病的“风险”，你会选择吗?研究人员决定检验以下假设：使用绝经后激素会增加患乳腺癌的风险。他们挑出500名新诊断为乳腺癌的女性，然年从同一个社区挑选出500名相同年龄的未患乳腺癌的女性。接着，他们向所有妇女询问过绝经后激素的使用情况。在患有乳腺癌的女性中，有250名报告使用了绝经后激素替代疗法；在没有乳腺癌的患者中，有175名报告使用了这种激素疗法。 现在本问题主要探讨乳腺癌的患病的一些概念，额外风险(excess),风险（risk）,相对危险度（relative risk，RR），优势比（Odds Ratio，0R）。有关这几个概念，请做出选择。QuestionA group of investigators decided to test the hypothesis that use of postmenopausal hormone replacement therapy increases the risk of breast cancer. They identified 500 women with newly diagnosed breast cancer, and 500 women of the same age, from the same neighbourhoods as the first group of women, who did not have breast cancer. Among the women with breast cancer, 250 reported having used postmenopausal hormones. Among those without breast cancer, 175 reported use of such hormones.Which of the following statements is or are true?a) The excess risk of breast cancer in women taking HRT is 15%—that is, (250-175)/500b) The risk of breast cancer in this group of women was 50%—that is, 500/(500+500)c) The relative risk of breast cancer in women taking HRT was 1.43—that is (250/500)/(175/500)d) The odds ratio for breast cancer in women taking HRT was 1.86—that is(250/250)/(175/325) AnswerIn a case control study incidence and absolute risks, including differences in absolute risk, cannot be calculated because cases and controls are selected by the researcher. Odds and odds ratios are used to express associations in case control studies. In carefully designed case control studies the odds ratio is the most accurate estimate of relative risk. For this to apply requires eitherr are outcomes or incidence based recruitment of cases and controls. 中文解释： 在病例对照研究中，由于研究人员选择了病例组和对照组，因此无法计算发生率和绝对风险、绝对风险差异、相对危险度指标（这些指标只有队列研究才能计算）。在病例对照研究中，比值和优势比用于表达关联性。在精心设计的病例对照研究中，优势比是相对危险度的最准确估算。 所以答案是选择 D 本号致力于医学科研方法分享，欢迎点击学习！
