STUDY OBJECTIVES To investigate the association between sleep duration and breast cancer incidence, we examined the association in a large UK prospective study and conducted a meta-analysis of prospective studies. METHODS In the Million Women Study, usual sleep duration over a 24-hour period was collected in 2001 for 713,150 participants without prior cancer, heart problems, stroke or diabetes (mean age=60 years). Follow-up for breast cancer was by record linkage to national cancer registry data for 14.3 years on average from the 3-year resurvey. Cox regression models yielded multivariable-adjusted breast cancer relative risks (RR) and 95% confidence intervals (CIs) for sleep duration categories. Published prospective studies of sleep duration and breast cancer risk were included in a meta-analysis, which estimated the inverse-variance weighted average of study-specific log RRs for short and for long versus average duration sleep. RESULTS After excluding the first five years to minimise reverse causation bias in the Million Women Study, 24,476 women developed breast cancer. Compared with 7-8 hours of sleep, the RRs for <6, 6, 9, and >9 hours of sleep were 1.01 (95%CI, 0.95-1.07), 0.99 (0.96-1.03), 1.01 (0.96-1.06), and 1.03 (0.95-1.12), respectively. In a meta-analysis of 14 prospective studies plus the Million Women Study, including 65,410 breast cancer cases, neither short (RR<7 hours=0.99 [0.98-1.01]) nor long (RR>8 hours=1.01 [0.98-1.04]) versus average duration sleep was associated with breast cancer risk. CONCLUSIONS The totality of the prospective evidence does not support an association between sleep duration and breast cancer risk.

中文翻译：

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睡眠时间和乳腺癌发病率：百万女性研究的结果和已发表前瞻性研究的荟萃分析

研究目的 为了调查睡眠持续时间与乳腺癌发病率之间的关系，我们在英国的一项大型前瞻性研究中检查了这种关系，并对前瞻性研究进行了荟萃分析。方法 在百万女性研究中，2001 年收集了 713,150 名既往没有癌症、心脏病、中风或糖尿病（平均年龄 = 60 岁）的参与者 24 小时内的正常睡眠时间。乳腺癌的随访是通过与国家癌症登记数据的记录联系，从 3 年的重新调查中平均持续 14.3 年。Cox 回归模型产生了多变量调整后的乳腺癌相对风险 (RR) 和睡眠持续时间类别的 95% 置信区间 (CI)。已发表的关于睡眠持续时间和乳腺癌风险的前瞻性研究被纳入一项荟萃分析，它估计了短期和长期睡眠与平均持续时间睡眠的研究特定对数 RR 的逆方差加权平均值。结果 在排除前五年以尽量减少百万女性研究中的反向因果偏差后，24,476 名女性患上了乳腺癌。与7-8小时睡眠相比，<6、6、9、>9小时睡眠的RRs分别为1.01（95%CI，0.95-1.07）、0.99（0.96-1.03）、1.01（0.96-1.06） , 和 1.03 (0.95-1.12), 分别。在对 14 项前瞻性研究和百万女性研究的荟萃分析中，包括 65,410 例乳腺癌病例，既不短（RR<7 小时=0.99 [0.98-1.01]）也不长（RR>8 小时=1.01 [0.98-1.04]） ) 与平均持续时间睡眠相比与乳腺癌风险相关。