Department of Surgery, Division of Public Health Sciences, Washington University in St. Louis School of Medicine, 660 S. Euclid Avenue, Campus Box 8100, St. Louis, MO 63110, USA,
Breast Cancer Res Treat. 2012 Sep;135(2):367-80. doi: 10.1007/s10549-012-2152-z. Epub 2012 Jul 20.
Studies show a protective relationship between physical activity and breast cancer risk across the life course from menarche to postmenopausal years. Mammographic breast density is a known and strong breast cancer risk factor. Whether the association of physical activity with breast cancer risk is mediated through mammographic breast density is poorly understood. This systematic review summarizes published studies that investigated the association between physical activity and mammographic breast density and discusses the methodological issues that need to be addressed. We included in this review studies that were published before October 31, 2011 that were accessible in full-text format and were published in English. We identified 20 studies through the PubMed Central, BioMed Central, Embase, and Scopus and using the search terms "physical activity and breast density" and "exercise and breast density" as well as through manual searches of the bibliographies of the articles identified in electronic searches. We found no evidence of association between physical activity and breast density across the studies by grouping them first by the timing of physical activity assessment (in adolescence, current/recent, past, and lifetime) and then by women's menopausal status (premenopausal and postmenopausal). Given the strength of the relationship between physical activity and breast cancer and the null findings of this review, it is unlikely that the effect of physical activity is mediated through an effect on breast density.
研究表明，从青春期到绝经后，体力活动与乳腺癌风险之间存在着贯穿整个生命过程的保护关系。乳腺 X 线照相密度是已知的强烈乳腺癌危险因素。体力活动与乳腺癌风险之间的关联是否通过乳腺 X 线照相密度来介导，这一点知之甚少。本系统综述总结了已发表的研究，这些研究调查了体力活动与乳腺 X 线照相密度之间的关系，并讨论了需要解决的方法学问题。我们纳入了这项综述的研究，这些研究发表于 2011 年 10 月 31 日之前，可全文获取，并以英文发表。我们通过 PubMed Central、BioMed Central、Embase 和 Scopus 以及使用搜索词“体力活动与乳腺密度”和“运动与乳腺密度”，并通过对电子搜索中确定的文章的参考文献进行手动搜索，确定了 20 项研究。我们发现，通过将体力活动评估的时间（青春期、当前/近期、过去和终身）首先分组，然后根据女性的绝经状态（绝经前和绝经后）分组，将这些研究分组后，体力活动与乳腺密度之间没有关联的证据。鉴于体力活动与乳腺癌之间的关系很强，而本综述的结果为阴性，因此体力活动的效果不太可能通过对乳腺密度的影响来介导。
