Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA.
Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO, USA.
Cancer Causes Control. 2022 Nov;33(11):1343-1353. doi: 10.1007/s10552-022-01617-3. Epub 2022 Aug 20.
A longer menarche-to-first pregnancy window of susceptibility (WOS) is associated with increased breast cancer risk. Whether physical activity, an established preventive risk factor, during the menarche-to-first pregnancy WOS offsets breast cancer risk overall or for specific molecular subtypes is unclear.
We examined the prospective association between physical activity during the menarche-to-first pregnancy WOS and breast cancer risk in the California Teachers Study (N = 78,940). Recreational physical activity at multiple timepoints were recalled at cohort entry, and converted to metabolic equivalent of task hours per week (MET-hrs/wk). We used multivariable Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).
We observed 5,157 invasive breast cancer cases over 21.6 years of follow-up. Longer menarche-to-first pregnancy WOS (≥ 20 vs. < 15 years) was associated with higher breast cancer risk (HR = 1.23, 95% CI = 1.13-1.34). Women with higher physical activity level during menarche-to-first pregnancy had lower risk of invasive breast cancer (≥ 40 vs. < 9 MET-hrs/wk: HR = 0.89, 95% CI = 0.83-0.97) and triple-negative subtype (≥ 40 vs. < 9 MET-hrs/wk: HR = 0.53, 95% CI = 0.32-0.87). No association was observed for luminal A-like and luminal B-like subtypes. Higher physical activity level was associated with lower breast cancer risk among women with moderate (15-19 years) menarche-to-first pregnancy intervals (≥ 40 vs. < 9 MET-hrs/wk: HR = 0.80, 95% CI = 0.69-0.92), but not with short (< 15 years) or long (≥ 20 years) intervals.
Physical activity during a WOS was associated with lower breast cancer risk in our cohort. Understanding timing of physical activity throughout the life course in relationship with breast cancer risk maybe important for cancer prevention strategies.
更长的月经初潮至首次妊娠窗口期（WOS）与乳腺癌风险增加相关。在月经初潮至首次妊娠 WOS 期间进行身体活动（已确定的预防风险因素）是否会整体或针对特定分子亚型抵消乳腺癌风险尚不清楚。
我们在加利福尼亚教师研究（N=78940）中研究了月经初潮至首次妊娠 WOS 期间身体活动与乳腺癌风险的前瞻性关联。在队列入组时回忆了多个时间点的休闲身体活动，并转换为每周代谢当量任务小时数（MET-hrs/wk）。我们使用多变量 Cox 比例风险模型来估计风险比（HR）和 95%置信区间（CI）。
我们在 21.6 年的随访中观察到 5157 例浸润性乳腺癌病例。较长的月经初潮至首次妊娠 WOS（≥20 年与<15 年）与更高的乳腺癌风险相关（HR=1.23，95%CI=1.13-1.34）。在月经初潮至首次妊娠期间身体活动水平较高的女性患浸润性乳腺癌的风险较低（≥40 年与<9 MET-hrs/wk：HR=0.89，95%CI=0.83-0.97）和三阴性亚型（≥40 年与<9 MET-hrs/wk：HR=0.53，95%CI=0.32-0.87）。在 luminal A 样和 luminal B 样亚型中未观察到关联。在中等（15-19 年）月经初潮至首次妊娠间隔的女性中，较高的身体活动水平与较低的乳腺癌风险相关（≥40 年与<9 MET-hrs/wk：HR=0.80，95%CI=0.69-0.92），但与较短（<15 年）或较长（≥20 年）间隔无关。
在我们的队列中，月经初潮至首次妊娠 WOS 期间的身体活动与乳腺癌风险降低相关。了解整个生命过程中身体活动与乳腺癌风险的时间关系可能对癌症预防策略很重要。
