BACKGROUND Previous studies suggest a protective role of physical activity in breast cancer risk, largely based on self-reported activity. We aimed to clarify this association by examining breast cancer risk in relation to self-reported physical activity, informed by accelerometer-based measures in a large subset of participants. METHODS We analysed data from 47,456 premenopausal and 126,704 postmenopausal women in UK Biobank followed from 2006 to 2014. Physical activity was self-reported at baseline, and at resurvey in a subsample of 6443 participants. Accelerometer data, measured from 2013 to 2015, were available in 20,785 women. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated by using multivariable-adjusted Cox regression. RESULTS A total of 3189 cases were diagnosed during follow-up (mean = 5.7 years). Women in the top compared with the bottom quartile of self-reported physical activity had a reduced risk of both premenopausal (RR 0.75; 95% CI 0.60-0.93) and postmenopausal breast cancer (RR 0.87; 95% CI 0.78-0.98), after adjusting for adiposity. In analyses utilising physical activity values assigned from accelerometer measurements, an increase of 5 milli-gravity was associated with a 21% (RR 0.79; 95% CI 0.66-0.95) reduction in premenopausal and a 16% (RR 0.84; 95% CI 0.73-0.96) reduction in postmenopausal breast cancer risk. CONCLUSIONS Greater physical activity is associated with a reduction in breast cancer risk, which appears to be independent of any association it may have on risk through its effects on adiposity.

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身体活动和乳腺癌风险：来自英国生物银行前瞻性队列的结果。

背景 先前的研究表明，身体活动在乳腺癌风险中的保护作用，主要是基于自我报告的活动。我们旨在通过检查与自我报告的体力活动相关的乳腺癌风险来阐明这种关联，这些活动是通过基于加速度计的大量参与者的测量得出的。方法 我们分析了 2006 年至 2014 年英国生物银行中 47,456 名绝经前妇女和 126,704 名绝经后妇女的数据。在基线时自我报告了身体活动，并在 6443 名参与者的子样本中进行了再调查。从 2013 年到 2015 年测量的加速度计数据可用于 20,785 名女性。使用多变量调整的 Cox 回归计算相对风险 (RR) 和 95% 置信区间 (CI)。结果 随访期间共诊断出 3189 例病例（平均 5.7 年）。与自我报告的体力活动最低四分位数相比，排在前四位的女性患绝经前 (RR 0.75；95% CI 0.60-0.93) 和绝经后乳腺癌 (RR 0.87；95% CI 0.78-0.98) 的风险均降低。调整肥胖。在利用加速度计测量值分配的身体活动值的分析中，5 毫重力的增加与 21% (RR 0.79; 95% CI 0.66-0.95) 的绝经前减少和 16% (RR 0.84; 95% CI 0.73) 相关-0.96) 绝经后乳腺癌风险降低。结论 更大的体力活动与乳腺癌风险的降低有关，这似乎与它通过对肥胖的影响可能与风险的任何关联无关。95% CI 0.60-0.93）和绝经后乳腺癌（RR 0.87；95% CI 0.78-0.98），在调整肥胖后。在利用加速度计测量值分配的身体活动值的分析中，5 毫重力的增加与 21% (RR 0.79; 95% CI 0.66-0.95) 的绝经前减少和 16% (RR 0.84; 95% CI 0.73) 相关-0.96) 绝经后乳腺癌风险降低。结论 更大的体力活动与乳腺癌风险的降低有关，这似乎与它通过对肥胖的影响可能与风险的任何关联无关。95% CI 0.60-0.93）和绝经后乳腺癌（RR 0.87；95% CI 0.78-0.98），在调整肥胖后。在利用加速度计测量值分配的身体活动值的分析中，5 毫重力的增加与 21% (RR 0.79; 95% CI 0.66-0.95) 的绝经前减少和 16% (RR 0.84; 95% CI 0.73) 相关-0.96) 绝经后乳腺癌风险降低。结论 更大的体力活动与乳腺癌风险的降低有关，这似乎与它通过对肥胖的影响可能与风险的任何关联无关。95% CI 0.66-0.95) 的绝经前乳腺癌风险降低和 16% (RR 0.84; 95% CI 0.73-0.96) 的绝经后乳腺癌风险。结论 更大的体力活动与乳腺癌风险的降低有关，这似乎与它通过对肥胖的影响可能与风险的任何关联无关。95% CI 0.66-0.95) 的绝经前乳腺癌风险降低和 16% (RR 0.84; 95% CI 0.73-0.96) 的绝经后乳腺癌风险。结论 更大的体力活动与乳腺癌风险的降低有关，这似乎与它通过对肥胖的影响可能与风险的任何关联无关。