Cancer Research Center of Hawai'i, 1236 Lauhala Street, Suite 407, Honolulu, HI 96813, USA.
Am J Epidemiol. 2010 May 1;171(9):960-8. doi: 10.1093/aje/kwq025. Epub 2010 Mar 30.
One potential mechanism by which physical activity may protect against breast cancer is by decreasing mammographic density. Percent mammographic density, the proportion of dense breast tissue area to total breast area, declines with age and is a strong risk factor for breast cancer. The authors hypothesized that women who were more physically active would have a greater decline in percent mammographic density with age, compared with less physically active women. The authors tested this hypothesis using longitudinal data (1996-2004) from 722 participants in the Study of Women's Health Across the Nation (SWAN), a multiethnic cohort of women who were pre- and early perimenopausal at baseline, with multivariable, repeated-measures linear regression analyses. During an average of 5.6 years, the mean annual decline in percent mammographic density was 1.1% (standard deviation = 0.1). A 1-unit increase in total physical activity score was associated with a weaker annual decline in percent mammographic density by 0.09% (standard error = 0.03; P = 0.01). Physical activity was inversely associated with the change in nondense breast area (P < 0.01) and not associated with the change in dense breast area (P = 0.17). Study results do not support the hypothesis that physical activity reduces breast cancer through a mechanism that includes reduced mammographic density.
体育活动可能通过降低乳腺密度来预防乳腺癌，这是一个潜在的机制。乳腺密度百分比，即致密乳腺组织面积占总乳腺面积的比例，随年龄的增长而下降，是乳腺癌的一个强危险因素。作者假设，与体力活动较少的女性相比，体力活动较多的女性乳腺密度百分比随年龄的增长下降幅度更大。作者使用来自全国妇女健康研究（SWAN）的 722 名参与者的纵向数据（1996-2004 年）检验了这一假设，SWAN 是一个多民族队列，基线时处于绝经前期和早期绝经后，采用多变量重复测量线性回归分析。在平均 5.6 年的时间里，乳腺密度百分比的年平均下降率为 1.1%（标准差=0.1）。总体力活动评分增加 1 个单位，与乳腺密度百分比的年下降率降低 0.09%相关（标准误差=0.03；P=0.01）。体力活动与非致密乳腺面积的变化呈负相关（P<0.01），与致密乳腺面积的变化无关（P=0.17）。研究结果不支持体力活动通过降低乳腺密度来降低乳腺癌风险的假说。
