Light at Night and Postmenopausal Breast Cancer Risk
This analysis examined an estimation of outdoor light at night (LAN) exposure from satellite imagery in association with postmenopausal breast cancer, utilizing data from the NIH-AARP Diet and Health Study. LAN was estimated at baseline from 1996, in 186,981 postmenopausal women. Over a 16 year follow up period, 12,318 cases of breast cancer were detected.
Comparing women in the lowest to highest quintile of baseline LAN, there was a 10% increase in the risk of postmenopausal breast cancer among women in the highest quintile of exposure (HR 1.10, p-trend=0.002). This association was stronger for ER+ breast cancer compared to ER(-) breast cancer (HR 1.12, p-trend=0.007).
The authors also found that important lifestyle factors, such as BMI, physical activity habits, hormone replacement therapy, smoking status, and alcohol consumption, along with environmental and social factors such as poverty rate, may interact with LAN to affect risk. For example, there were somewhat stronger associations for women who were current smokers, and also stronger associations for women consuming ≥ 1 alcohol drink daily. LAN may influence postmenopausal breast cancer risk via synergistic interactions with these factors, potentially via alteration of melatonin or estrogen pathways.
Citation:
Xiao Q, James P, Breheny P, et al. Outdoor light at night and postmenopausal breast cancer risk in the NIH-AARP diet and health study. Int J Cancer. 2020; 147(9):2363-2372. doi:10.1002/ijc.33016
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