Friedenreich C M, Rohan T E
Division of Epidemiology, Prevention and Screening, Alberta Cancer Board, Calgary, Canada.
Epidemiology. 1995 May;6(3):311-7. doi: 10.1097/00001648-199505000-00021.
Breast cancer risk is influenced by endogenous hormones. Physical activity may offer one means for the primary prevention of breast cancer through its influence on ovarian hormones. This influence is manifested by changes in age at menarche and the number and nature of ovulatory menstrual cycles, factors that themselves are related to breast cancer risk. Animal experimental studies show that breast cancer risk is decreased by exercise at the time of tumor initiation but not necessarily by exercise during tumor promotion. Epidemiologic studies indicate, overall, a decreased risk of breast cancer among those women who are more physically active, whereas experimental studies of the effects of exercise in women have shown that exercise can influence characteristics of the menstrual cycle. Nevertheless, the experimental studies in women and epidemiologic studies of physical activity and breast cancer risk have been hampered by a number of methodologic limitations. The major problems in the epidemiologic studies include crude and incomplete measurements of physical activity over a woman's lifetime and inadequate control for potential confounding factors. Experimental studies of the effects of physical activity on menstrual activity in women have not adequately quantified the intensity of activity and the resultant effects on menstrual cycle changes.
乳腺癌风险受内源性激素影响。身体活动可能通过对卵巢激素的影响为乳腺癌的一级预防提供一种手段。这种影响表现为初潮年龄的变化以及排卵性月经周期的数量和性质的改变，而这些因素本身与乳腺癌风险相关。动物实验研究表明，在肿瘤起始阶段进行运动可降低乳腺癌风险，但在肿瘤促进阶段运动不一定能降低风险。总体而言，流行病学研究表明，身体活动较多的女性患乳腺癌的风险降低，而对女性运动效果的实验研究表明，运动可影响月经周期特征。然而，女性的实验研究以及身体活动与乳腺癌风险的流行病学研究受到了一些方法学限制的阻碍。流行病学研究中的主要问题包括对女性一生身体活动的粗略和不完整测量以及对潜在混杂因素的控制不足。关于身体活动对女性月经活动影响的实验研究尚未充分量化活动强度及其对月经周期变化的最终影响。
