Light at Night and Breast Cancer Risk in California Teachers
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: While it has long been noted that women living in industrialized areas are more likely to get breast cancer than their rural-dwelling counterparts, reasons for the urban excess of breast cancer remain enigmatic. One provocative hypothesis that has emerged is that increased exposure to night time lighting associated with industrialization results in circadian disruption that through a variety of potential mechanisms could increase the risk of breast cancer. While there is convincing laboratory evidence that circadian disruption mediated by light-at-night exposures promotes mammary carcinogenesis in rodents, the degree to which light-at-night plays a role in the development of breast cancer in humans is not known. 
 
 
 
 
 
 
 
 Direct assessment of light-at-night exposures and breast cancer risk among human populations has been hampered by limitations in ways to assess exposure. This proposal capitalizes on newly-available satellite data on night-time illumination, on a well-developed urinary biomarker of melatonin (the primary hormonal modulator of circadian rhythms in mammals), and on existing survey data on indoor indicators of light-at-night exposures, to evaluate and develop methods to explore the relationship between these exposures and breast cancer risk among members of the California Teachers Study (CTS), a large, geographically diverse cohort of women for whom extensive information on known breast cancer risk factors is available.
 
 
 
 
 
 
 
 This project will analyze approximately 125,000 CTS cohort members who live in California. Ambient light-at-night values will be based on satellite imagery data obtained from the U.S. Defense Meteorological Satellite Program’s Operational Linescan System and assigned to CTS participants based on where they live. Through extensive exploratory data analyses we will identify the best strategy for using the satellite data to assign a value of night-time luminance to each individual in the cohort for the period of the study. Indicators of indoor light-at-night will be derived from prior CTS survey questions on sleep habits and use of night-time lighting in the home. Next, statistical models will be used to estimate the risk of breast cancer, taking into account other known breast cancer risk factors. These analyses will be based on the 4,800 cases of invasive breast cancer we anticipate will be diagnosed among CTS participants from 1995 - 2008. Finally, laboratory assays for urinary concentrations of 6- suflatoxymelatonin, the primary metabolite of melatonin, will be conducted on approximately 300 stored CTS urine specimens and multivariable statistical models will be used to identify important predictors of those levels in participating women.
 
 
 
 
 
 
 
 This study would provide critical preliminary information regarding the role of night time lighting in the etiology of breast cancer. Given that light-at-night exposures are prevalent and potentially modifiable through relatively simple policy and behavioral interventions, it offers tremendous potential to identify new avenues for breast cancer prevention.