Davis S, Mirick D K, Stevens R G
Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA.
J Natl Cancer Inst. 2001 Oct 17;93(20):1557-62. doi: 10.1093/jnci/93.20.1557.
Exposure to light at night may increase the risk of breast cancer by suppressing the normal nocturnal production of melatonin by the pineal gland, which, in turn, could increase the release of estrogen by the ovaries. This study investigated whether such exposure is associated with an increased risk of breast cancer in women.
Case patients (n = 813), aged 20-74 years, were diagnosed from November 1992 through March 1995; control subjects (n = 793) were identified by random-digit dialing and were frequency matched according to 5-year age groups. An in-person interview was used to gather information on sleep habits and bedroom lighting environment in the 10 years before diagnosis and lifetime occupational history. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by use of conditional logistic regression, with adjustment for other potential risk factors.
Breast cancer risk was increased among subjects who frequently did not sleep during the period of the night when melatonin levels are typically at their highest (OR = 1.14 for each night per week; 95% CI = 1.01 to 1.28). Risk did not increase with interrupted sleep accompanied by turning on a light. There was an indication of increased risk among subjects with the brightest bedrooms. Graveyard shiftwork was associated with increased breast cancer risk (OR = 1.6; 95% CI = 1.0 to 2.5), with a trend of increased risk with increasing years and with more hours per week of graveyard shiftwork (P =.02, Wald chi-squared test).
The results of this study provide evidence that indicators of exposure to light at night may be associated with the risk of developing breast cancer.
夜间暴露于光线下可能会通过抑制松果体正常的夜间褪黑素分泌而增加患乳腺癌的风险，而这反过来又可能增加卵巢雌激素的释放。本研究调查了这种暴露是否与女性患乳腺癌风险增加有关。
1992年11月至1995年3月期间诊断出813例年龄在20 - 74岁之间的病例患者；通过随机数字拨号确定793名对照对象，并按5岁年龄组进行频率匹配。通过面对面访谈收集诊断前10年的睡眠习惯和卧室照明环境信息以及终生职业史。使用条件逻辑回归估计比值比（OR）和95%置信区间（CI），并对其他潜在风险因素进行调整。
在褪黑素水平通常最高的夜间时段经常不睡觉的受试者中，患乳腺癌的风险增加（每周每夜OR = 1.14；95%CI = 1.01至1.28）。睡眠中断并开灯的情况下风险并未增加。卧室最亮的受试者有风险增加的迹象。从事夜班工作与患乳腺癌风险增加有关（OR = 1.6；95%CI = 1.0至2.5），且随着从事夜班工作的年限增加和每周工作小时数增多，风险有增加趋势（P =.02，Wald卡方检验）。
本研究结果提供了证据，表明夜间暴露于光线下的指标可能与患乳腺癌的风险有关。
