Bernstein L, Henderson B E, Hanisch R, Sullivan-Halley J, Ross R K
Department of Preventive Medicine, University of Southern California School of Medicine, Los Angeles 90033.
J Natl Cancer Inst. 1994 Sep 21;86(18):1403-8. doi: 10.1093/jnci/86.18.1403.
Epidemiologic evidence strongly suggests that cumulative exposure to ovarian hormones is a determinant of breast cancer risk. Because physical activity can modify menstrual cycle patterns and alter the production of ovarian hormones, it may reduce breast cancer risk; yet few epidemiologic studies have assessed this relationship.
The major objective of this study was to determine whether young women (aged 40 and younger) who regularly participated in physical exercise activities during their reproductive years had a reduced risk of breast cancer.
Using a case-control design, we conducted personal interviews of a total of 545 women (aged 40 and younger at diagnosis) who had been newly diagnosed with in situ or invasive breast cancer between July 1, 1983, and January 1, 1989, and a total of 545 control subjects. Case patients and control subjects were individually matched on date of birth (within 36 months), race (white), parity (nulliparous versus parous), and neighborhood of residence. Lifetime histories of participation in physical exercise activities on a regular basis were obtained during the personal interview.
After adjustment for potential confounding factors, we found that the average number of hours spent in physical exercise activities per week from menarche to 1 year prior to the case patient's diagnosis was a significant predictor of reduced breast cancer risk (two-sided P for trend < .0001). The odds ratio (OR) of breast cancer among women who, on average, spent 3.8 or more hours per week participating in physical exercise activities was 0.42 (95% confidence limits [CLs] = 0.27, 0.64) relative to inactive women. The effect was stronger among women who had had a full-term pregnancy. Comparing most active (> or = 3.8 hours/wk of exercise) women to inactive women, the ORs were 0.28 (95% CL = 0.16, 0.50) for parous and 0.73 (95% CL = 0.38, 1.41) for nulliparous women.
Most previously identified risk factors for breast cancer are reproductive and menstrual events that cannot be readily altered. The protective effect of exercise on breast cancer risk in the women whom we studied suggests that physical activity offers one modifiable lifestyle characteristic that may substantially reduce a woman's lifetime risk of breast cancer.
Whether the protective effects of exercise on breast cancer risk are due to alterations in ovarian function and whether they extend into women's menopausal years need to be established. Our results suggest that implementation of regular physical exercise programs as a critical component of a healthy lifestyle should be a high priority for adolescent and adult women.
流行病学证据有力地表明，卵巢激素的累积暴露是乳腺癌风险的一个决定因素。由于体育活动可改变月经周期模式并改变卵巢激素的分泌，故其可能降低乳腺癌风险；然而，很少有流行病学研究评估过这种关系。
本研究的主要目的是确定在生育期定期参加体育锻炼活动的年轻女性（40岁及以下）患乳腺癌的风险是否降低。
采用病例对照设计，我们对1983年7月1日至1989年1月1日期间新诊断为原位或浸润性乳腺癌的545名女性（诊断时年龄为40岁及以下）以及545名对照对象进行了个人访谈。病例患者和对照对象按出生日期（36个月内）、种族（白人）、生育情况（未生育与已生育）和居住社区进行个体匹配。在个人访谈中获取了定期参加体育锻炼活动的终生史。
在对潜在混杂因素进行调整后，我们发现从初潮到病例患者诊断前1年每周花费在体育锻炼活动上的平均小时数是乳腺癌风险降低的一个显著预测因素（趋势的双侧P<0.0001）。平均每周花费3.8小时或更多时间参加体育锻炼活动的女性患乳腺癌的优势比（OR）相对于不活动的女性为0.42（95%置信区间[CL]=0.27，0.64）。在足月妊娠的女性中这种效应更强。将最活跃（锻炼≥3.8小时/周）的女性与不活动的女性进行比较，已生育女性的OR为0.28（95%CL=0.16，0.50），未生育女性的OR为0.73（95%CL=0.38，1.41）。
大多数先前确定的乳腺癌风险因素是无法轻易改变的生殖和月经事件。我们研究的女性中体育锻炼对乳腺癌风险的保护作用表明，体育活动提供了一种可改变的生活方式特征，可能会大幅降低女性一生患乳腺癌的风险。
体育锻炼对乳腺癌风险的保护作用是否归因于卵巢功能的改变以及这种作用是否延伸至女性绝经后仍有待确定。我们的结果表明，实施定期体育锻炼计划作为健康生活方式的关键组成部分应是青少年和成年女性的高度优先事项。
