A case-referent study: light at night and breast cancer risk in Georgia

Abstract

BackgroundLiterature has identified detrimental health effects from the indiscriminate use of artificial nighttime light. We examined the co-distribution of light at night (LAN) and breast cancer (BC) incidence in Georgia, with the goal to contribute to the accumulating evidence that exposure to LAN increases risk of BC.MethodsUsing Georgia Comprehensive Cancer Registry data (2000–2007), we conducted a case-referent study among 34,053 BC cases and 14,458 lung cancer referents. Individuals with lung cancer were used as referents to control for other cancer risk factors that may be associated with elevated LAN, such as air pollution, and since this cancer type was not previously associated with LAN or circadian rhythm disruption. DMSP-OLS Nighttime Light Time Series satellite images (1992–2007) were used to estimate LAN levels; low (0–20 watts per sterradian cm2), medium (21–41 watts per sterradian cm2), high (>41 watts per sterradian cm2). LAN levels were extracted for each year of exposure prior to case/referent diagnosis in ArcGIS.ResultsOdds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models controlling for individual-level year of diagnosis, race, age at diagnosis, tumor grade, stage; and population-level determinants including metropolitan statistical area (MSA) status, births per 1,000 women aged 15–50, percentage of female smokers, MSA population mobility, and percentage of population over 16 in the labor force. We found that overall BC incidence was associated with high LAN exposure (OR = 1.12, 95% CI [1.04, 1.20]). When stratified by race, LAN exposure was associated with increased BC risk among whites (OR = 1.13, 95% CI [1.05, 1.22]), but not among blacks (OR = 1.02, 95% CI [0.82, 1.28]).ConclusionsOur results suggest positive associations between LAN and BC incidence, especially among whites. The consistency of our findings with previous studies suggests that there could be fundamental biological links between exposure to artificial LAN and increased BC incidence, although additional research using exposure metrics at the individual level is required to confirm or refute these findings.

Artificial light at night: melatonin as a mediator between the environment and epigenome

“…In the past decade, several epidemiological studies have investigated the co-distribution between breast cancer incidence and light pollution [19][20][21][22]. These studies and others find compelling evidence supporting a potential role of electric light at night on breast cancer risk.…”

Benefits and costs of artificial nighttime lighting of the environment

“…The effects were not linked to a particular lighting technology but due directly or indirectly to artificial nighttime light itself. Studies have variously documented geographic and chronological covariance between patterns of nighttime lighting and the incidence of breast cancer and obesity (Kloog et al 2010;Wyse et al 2011;Bauer et al 2013). In the case of obesity, researchers concluded that chronic circadian desynchrony, defined as small daily changes in the 24 h light:dark cycle as induced by electric lighting, are associated with increasing weight gain and metabolic disorders such as diabetes in both experimental animals and in shift workers (Wyse et al 2011).…”

Spatiotemporal patterns of outdoor artificial nighttime lights exposure in the Republic of Korea between 1995 and 2010

“…The National Geophysical Data Center (NGDC) of the US National Oceanic and Atmospheric Administration (NOAA) provides time-series DMSP OLS images (Elvidge et al 2007). DMSP OLS imagery has been used in a wide variety of study areas such as urbanization (Lo 2002), population and socioeconomic estimation (Welch 1980;Sutton et al 2001;Doll, Muller, and Morley 2006;Gallaway, Olsen, and Mitchell 2010), and human health (Kloog et al 2008(Kloog et al , 2010Bauer et al 2013).…”