Outdoor light at night and postmenopausal breast cancer risk in the NIH-AARP diet and health study

Qian Xiao, Peter James, Patrick Breheny, Peng Jia, Yikyung Park, Dong Zhang, Jared A. Fisher, Mary H. Ward, Rena R. Jones

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Circadian disruption may play a role in breast carcinogenesis. Previous studies reported relationships between outdoor light at night (LAN) and the breast cancer risk, but their findings are mixed. There is also a need to examine LAN and breast cancer incidence according to different individual and environmental characteristics to identify subpopulations at greater risk associated with LAN exposure. We studied residential outdoor LAN estimated from satellite imagery at baseline (1996) in relation to postmenopausal breast cancer incidence over ~16 years of follow-up in 186 981 postmenopausal women including 12 318 incident postmenopausal breast cancer cases in the NIH-AARP Diet and Health Study. We used Cox proportional hazards models to estimate hazard ratios (HR) and two-sided 95% confidence intervals (CI) of the relationship between quintiles of LAN and postmenopausal breast cancer risk, overall and by hormone receptor status and cancer stage. We found that when compared to women in the lowest quintile of baseline LAN, those in the highest quintile had a 10% increase in postmenopausal breast cancer risk (HR (95% CI), 1.10 (1.02, 1.18), P-trend,.002). The association appeared to be stronger for estrogen receptor (ER) positive breast cancer (1.12 [1.02, 1.24],.007) than for ER-negative cancer (1.07 [0.85, 1.34],.66). Our findings also suggested that the relationship between LAN and breast cancer risk may differ by individual characteristics, such as smoking, alcohol drinking, sleep duration and BMI, and neighborhood environment. In conclusion, our study suggests that higher outdoor LAN exposure may be a risk factor for postmenopausal breast cancer.

Original languageEnglish
Pages (from-to)2363-2372
Number of pages10
JournalInternational Journal of Cancer
Issue number9
StatePublished - Nov 1 2020


  • circadian disruption
  • outdoor light at night
  • postmenopausal breast cancer
  • prospective cohort


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