Enger S M, Ross R K, Paganini-Hill A, Bernstein L
Research and Evaluation Department, Kaiser Permanente Medical Care Program, Southern California, Pasadena 91188, USA.
Cancer Epidemiol Biomarkers Prev. 1998 May;7(5):365-9.
Results of studies of breastfeeding and postmenopausal breast cancer risk have been inconsistent, with many investigators concluding that breastfeeding does not influence risk. We examined whether breastfeeding reduces postmenopausal breast cancer risk as well as the details of this relationship, including possible modification in risk by the age that a woman first breastfed a child and the number of children she breastfed. This population-based case-control study compared 974 women who were residents of Los Angeles County and newly diagnosed with breast cancer to 973 women with no history of breast cancer who were matched to patients by age (within 3 years) and neighborhood of residence. Subjects were parous and postmenopausal. Breast cancer patients were ages 55-64 years at diagnosis. Women who breastfed at least 16 months experienced a reduced odds of breast cancer relative to women who never breastfed (odds ratio, 0.73; 95% confidence interval, 0.52-1.01). Risk decreased as the number of children breastfed increased, but the association was attenuated after accounting for lifetime duration of breastfeeding. Breast cancer risk was 30% lower among women ages 20-24 years at first breastfeeding than women who had never breastfed (odds ratio, 0.69; 95% confidence interval, 0.54-0.88), independent of the effect of age at first birth. This study provides some evidence that the protective effect of breastfeeding persists into the postmenopausal years. The potential for nondifferential error in recall of breastfeeding habits among postmenopausal patients and controls may explain the inconsistent results observed across studies and underscores the need for careful assessment of this relationship.
关于母乳喂养与绝经后乳腺癌风险的研究结果并不一致，许多研究人员得出结论认为母乳喂养不会影响风险。我们研究了母乳喂养是否会降低绝经后乳腺癌风险以及这种关系的细节，包括女性首次母乳喂养孩子的年龄和母乳喂养孩子的数量对风险的可能影响。这项基于人群的病例对照研究将974名洛杉矶县居民且新诊断为乳腺癌的女性与973名无乳腺癌病史的女性进行了比较，后者按年龄（相差3岁以内）和居住社区与患者进行匹配。研究对象均为经产妇且已绝经。乳腺癌患者诊断时年龄在55 - 64岁之间。与从未母乳喂养的女性相比，母乳喂养至少16个月的女性患乳腺癌的几率降低（比值比为0.73；95%置信区间为0.52 - 1.01）。随着母乳喂养孩子数量的增加，风险降低，但在考虑母乳喂养的终生时长后，这种关联减弱。首次母乳喂养年龄在20 - 24岁的女性患乳腺癌的风险比从未母乳喂养的女性低30%（比值比为0.69；95%置信区间为0.54 - 0.88），这与首次生育年龄的影响无关。这项研究提供了一些证据表明母乳喂养的保护作用会持续到绝经后。绝经后患者和对照在回忆母乳喂养习惯时可能存在无差异误差，这或许可以解释不同研究中观察到的不一致结果，并强调了仔细评估这种关系的必要性。
