Light at night and the risk of breast cancer: Findings from the Sister study

Marina R. Sweeney; Hazel B. Nichols; Rena R. Jones; Andrew F. Olshan; Alexander P. Keil; Lawrence S. Engel; Peter James; Chandra L. Jackson; Dale P. Sandler; Alexandra J. White

Environment International (Nov 2022)

Light at night and the risk of breast cancer: Findings from the Sister study

Marina R. Sweeney,
Hazel B. Nichols,
Rena R. Jones,
Andrew F. Olshan,
Alexander P. Keil,
Lawrence S. Engel,
Peter James,
Chandra L. Jackson,
Dale P. Sandler,
Alexandra J. White

Affiliations

Marina R. Sweeney: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA; Epidemiology Branch, National Institute of Environmental Health Sciences, Durham, NC, USA
Hazel B. Nichols: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA
Rena R. Jones: Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA
Andrew F. Olshan: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA
Alexander P. Keil: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA
Lawrence S. Engel: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA
Peter James: Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA; Department of Environmental Health, Harvard TH Chan School of Public Health, Boston, MA, USA
Chandra L. Jackson: Epidemiology Branch, National Institute of Environmental Health Sciences, Durham, NC, USA; Division of Intramural Research, National Institute on Minority Health and Health Disparities, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA
Dale P. Sandler: Epidemiology Branch, National Institute of Environmental Health Sciences, Durham, NC, USA
Alexandra J. White: Epidemiology Branch, National Institute of Environmental Health Sciences, Durham, NC, USA; Corresponding author.

Journal volume & issue: Vol. 169
p. 107495

Abstract

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Background: Light at night (LAN) may alter estrogen regulation through circadian disruption. High levels of outdoor LAN may increase breast cancer risk, but studies have largely not considered possible residual confounding from correlated environmental exposures. We evaluated the association between indoor and outdoor LAN and incident breast cancer. Methods: In 47,145 participants in the prospective Sister Study cohort living in the contiguous U.S., exposure to outdoor LAN was determined using satellite-measured residential data and indoor LAN was self-reported (light/TV on, light from outside the room, nightlight, no light). We used Cox proportional hazards models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations between outdoor and indoor LAN and breast cancer risk. Models were adjusted for age, race/ethnicity, educational attainment, annual household income, neighborhood disadvantage, latitude, and population density as a proxy for urbanicity. To evaluate the potential for residual confounding of the outdoor LAN and breast cancer relationship by factors associated with urbanicity, we considered further adjustment for exposures correlated with outdoor LAN including NO2 [Spearman correlation coefficient, rho (ρ) = 0.78], PM2.5 (ρ = 0.36), green space (ρ = − 0.41), and noise (ρ = 0.81). Results: During 11 years of follow-up, 3,734 breast cancer cases were identified. Outdoor LAN was modestly, but non-monotonically, associated with a higher risk of breast cancer (Quintile 4 vs 1: HR = 1.10, 95% CI: 0.99–1.22; Quintile 5 vs 1: HR = 1.04, 95% CI: 0.93–1.16); however, no association was evident after adjustment for correlated ambient exposures (Quintile 4 vs 1: HR = 0.99, 95% CI: 0.86–1.14; Quintile 5 vs 1: HR = 0.89, 95% CI: 0.74–1.06). Compared to those with no indoor LAN exposure, sleeping with a light or TV on was associated with a HR = 1.09 (95% CI: 0.97–1.23) in the adjusted model. Conclusions: Outdoor LAN does not appear to increase the risk of breast cancer after adjustment for correlated environmental exposures.

Published in Environment International

ISSN: 0160-4120 (Print)
Publisher: Elsevier
Country of publisher: United Kingdom
LCC subjects: Geography. Anthropology. Recreation: Environmental sciences
Website: https://www.journals.elsevier.com/environment-international

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