研究：夜间室外光照易提高患乳腺癌的风险

Women who live in areas with higher levels of outdoor light at night may be at higher risk for breast cancer, according to a study from Harvard T.H. Chan School of Public Health. The link was stronger among women who worked night shifts.

哈佛大学陈曾熙公共卫生学院的一项研究表示，那些在夜晚户外光线较强地区生活的女性更容易患上乳腺癌。对于那些上夜班的女性来说，这之间有着更紧密的联系。

Previous studies have suggested that exposure to light at night may lead to decreased levels of the hormone melatonin , which can disrupt circadian rhythms—our internal “clocks” that govern sleepiness and alertness—and, in turn, lead to increased breast cancer risk.

先前的研究指出，晚上暴露于光线中可能会降低褪黑激素的含量，扰乱生理节奏，也就是我们身体内部控制睡意和敏捷性的“生物钟”，继而增加罹患乳腺癌的风险。

The new study, the most comprehensive to date to examine possible links between outdoor light at night and breast cancer, looked at data from nearly 110,000 women enrolled in the Nurses’ Health study II from 1989-2013. The researchers linked data from satellite images of Earth taken at nighttime to residential addresses for each study participant, and also considered the influence of night shift work. The study also factored in detailed information on a variety of health and socioeconomic factors among participants.

迄今为止最全面的一项新研究针对1989年至2013年在护士健康研究II中登记的近110,000位女性的数据，调查了夜晚户外灯光与乳腺癌之间可能存在的联系。研究人员把地球夜间的卫星图像数据与每位研究参与者的住址联系在一起，并考虑了夜班工作的影响。该研究还把参与者的健康以及社会经济等多种因素的详细信息考虑在内。

Women exposed to the highest levels of outdoor light at night—those in the top fifth—had an estimated 14% increased risk of breast cancer during the study period, as compared with women in the bottom fifth of exposure, the researchers found. As levels of outdoor light at night increased, so did breast cancer rates.

研究人员发现，在这期间，那些在夜晚暴露于高强度光照下的女性（光照强度排在前五位）比那些在低光照环境下生活的女性（光照强度排在后五位）患上乳腺癌的风险预估增加了14%。随着夜晚户外光照强度的增加，罹患乳腺癌的几率也相应上涨。

However, the association between outdoor light at night and breast cancer was found only among women who were premenopausal and those who were current or past smokers. In addition, the link was stronger among women who worked night shifts, suggesting that exposure to light at night and night shift work contribute jointly to breast cancer risk.

不过，夜晚户外光照与乳腺癌之间的关联只发现于那些绝经前期的女性以及那些当前或过去抽烟的女性。此外，对于那些上夜班的女性，这种联系要更紧密一些，这表示，夜晚暴露于光照下与夜班工作可能会共同增加罹患乳腺癌的风险。