Bernstein L, Ross R K, Lobo R A, Hanisch R, Krailo M D, Henderson B E
Br J Cancer. 1987 Jun;55(6):681-5. doi: 10.1038/bjc.1987.139.
Girls who engage in strenuous physical activity are often amenorrheic and have recently been reported to be at a reduced risk of breast cancer. To determine whether moderate amounts of exercise affect menstrual cycle patterns and ovulatory frequency in young postmenarcheal girls, the menstrual cycles and physical activity patterns of 168 high school girls were monitored for a 6 month period. Anovulatory cycles were associated with later age at menarche, fewer elapsed years since menarche and greater levels of energy expended per week in physical activity. After adjusting for age at menarche and years since menarche, there was a significant dose-related trend in the risk of anovular menstrual cycles associated with increasing levels of physical activity (1-sided P = 0.03). Major determinants of average cycle length were weekly average energy expenditure (less than or equal to 750 kcal wk-1 associated with cycles that were on average 2.4 days longer), age at menarche (an increase of 0.7 days per year of age) and race (Asians having cycles about 1.9 days longer than Caucasians). Because a major determinant of breast cancer risk may be the cumulative number of ovulatory cycles, these data suggest that regular participation in moderate physical activity, by reducing the frequency of ovulatory cycles in adolescence, may provide an opportunity for the primary prevention of breast cancer.
从事剧烈体育活动的女孩常常闭经，最近有报道称她们患乳腺癌的风险降低。为了确定适量运动是否会影响初潮后年轻女孩的月经周期模式和排卵频率，对168名高中女生的月经周期和体育活动模式进行了为期6个月的监测。无排卵周期与初潮年龄较大、初潮后经过的年数较少以及每周体育活动消耗的能量水平较高有关。在对初潮年龄和初潮后年数进行调整后，与体育活动水平增加相关的无排卵月经周期风险存在显著的剂量相关趋势（单侧P = 0.03）。平均周期长度的主要决定因素是每周平均能量消耗（每周小于或等于750千卡与平均长2.4天的周期相关）、初潮年龄（每年增加0.7天）和种族（亚洲人的周期比白种人长约1.9天）。由于乳腺癌风险的一个主要决定因素可能是排卵周期的累积数量，这些数据表明，通过减少青春期的排卵周期频率，定期参与适量体育活动可能为乳腺癌的一级预防提供机会。
