Dataset Information

Outdoor Light at Night and Breast Cancer Incidence in the Nurses' Health Study II.

ABSTRACT:

Background

Animal and epidemiologic studies suggest that exposure to light at night (LAN) may disrupt circadian patterns and decrease nocturnal secretion of melatonin, which may disturb estrogen regulation, leading to increased breast cancer risk.

Objectives

We examined the association between residential outdoor LAN and breast cancer incidence using data from the nationwide U.S.-based Nurses' Health Study II cohort.

Methods

We followed 109,672 women from 1989 through 2013. Cumulative LAN exposure was estimated using time-varying satellite data for a composite of persistent nighttime illumination at ?1?km² scale for each residence during follow-up. Incident invasive breast cancer cases were confirmed by medical record review. We used Cox proportional hazard models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for anthropometric, reproductive, lifestyle, and socioeconomic risk factors.

Results

Over 2,187,425 person-years, we identified 3,549 incident breast cancer cases. Based on a fully adjusted model, the estimated HR for incident breast cancer with an interquartile range (IQR) (31.6?nW/cm²/sr) increase in cumulative average outdoor LAN was 1.05 (95% CI: 1.00, 1.11). An association between LAN and breast cancer appeared to be limited to women who were premenopausal at the time of a case [HR=1.07 (95% CI: 1.01, 1.14) based on 1,973 cases vs. HR=1.00 (95% CI: 0.91, 1.09) based on 1,172 cases in postmenopausal women; p-interaction=0.08]. The LAN-breast cancer association was observed only in past and current smokers at the end of follow-up [HR=1.00 (95% CI: 0.94, 1.07) based on 2,215 cases in never smokers; HR=1.10 (95% CI: 1.01, 1.19) based on 1,034 cases in past smokers vs. HR=1.21 (95% CI: 1.07, 1.37) for 300 cases in current smokers; p-interaction=0.08].

Conclusions

Although further work is required to confirm our results and to clarify potential mechanisms, our findings suggest that exposure to residential outdoor light at night may contribute to invasive breast cancer risk. https://doi.org/10.1289/EHP935.

SUBMITTER: James P

PROVIDER: S-EPMC5783660 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Publications

Outdoor Light at Night and Breast Cancer Incidence in the Nurses' Health Study II.

James Peter P Bertrand Kimberly A KA Hart Jaime E JE Schernhammer Eva S ES Tamimi Rulla M RM Laden Francine F

Environmental health perspectives 20170817 8

<h4>Background</h4>Animal and epidemiologic studies suggest that exposure to light at night (LAN) may disrupt circadian patterns and decrease nocturnal secretion of melatonin, which may disturb estrogen regulation, leading to increased breast cancer risk.<h4>Objectives</h4>We examined the association between residential outdoor LAN and breast cancer incidence using data from the nationwide U.S.-based Nurses' Health Study II cohort.<h4>Methods</h4>We followed 109,672 women from 1989 through 2013. ...[more]

PMID: 28886600

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Dataset Information

Outdoor Light at Night and Breast Cancer Incidence in the Nurses' Health Study II.

Background

Objectives

Methods

Results

Conclusions

Publications

Outdoor Light at Night and Breast Cancer Incidence in the Nurses' Health Study II.

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