囧研究：夜間室外光照易提高患乳腺癌的風險

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.

哈佛大學陳曾熙公共衛生學院的一項研究表示，那些在夜晚戶外光線較強地區生活的女性更容易患上乳腺癌。對於那些上夜班的女性來說，這之間有著更緊密的聯繫。

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，晚上暴露於光線中可能會降低褪黑激素的含量，擾亂生理節奏，也就是我們身體內部控制睡意和敏捷性的「生物鐘」，繼而增加罹患乳腺癌的風險。

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.

迄今為止最全面的一項新研究針對1989年至2013年在護士健康研究II中登記的近110,000位女性的數據，調查了夜晚戶外燈光與乳腺癌之間可能存在的聯繫。研究人員把地球夜間的衛星圖像數據與每位研究參與者的住址聯繫在一起，並考慮了夜班工作的影響。該研究還把參與者的健康以及社會經濟等多種因素的詳細信息考慮在內。

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.

研究人員發現，在這期間，那些在夜晚暴露於高強度光照下的女性（光照強度排在前五位）比那些在低光照環境下生活的女性（光照強度排在後五位）患上乳腺癌的風險預估增加了14%。隨著夜晚戶外光照強度的增加，罹患乳腺癌的幾率也相應上漲。

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.

不過，夜晚戶外光照與乳腺癌之間的關聯只發現於那些絕經前期的女性以及那些當前或過去抽煙的女性。此外，對於那些上夜班的女性，這種聯繫要更緊密一些，這表示，夜晚暴露於光照下與夜班工作可能會共同增加罹患乳腺癌的風險。