Abstract
BackgroundThere is accumulating evidence that circadian disruption, mediated by alterations in melatonin levels, may play an etiologic role in a wide variety of diseases. The degree to which light-at-night (LAN) and other factors can alter melatonin levels is not well-documented. Our primary objective was to evaluate the degree to which estimates of outdoor environmental LAN predict 6-sulftoxymelatonin (aMT6s), the primary urinary metabolite of melatonin. We also evaluated other potential behavioral, sociodemographic, and anthropomorphic predictors of aMT6s.MethodsStudy participants consisted of 303 members of the California Teachers Study who provided a 24-hour urine specimen and completed a self-administered questionnaire in 2000. Urinary aMT6s was measured using the Bühlmann ELISA. Outdoor LAN levels were estimated from satellite imagery data obtained from the U.S. Defense Meteorological Satellite Program’s (DMSP) Operational Linescan System and assigned to study participants’ geocoded residential address. Information on other potential predictors of aMT6s was derived from self-administered surveys. Neighborhood socioeconomic status (SES) was based on U.S. Census block group data.ResultsLower aMT6s levels were significantly associated with older age, shorter nights, and residential locations in lower SES neighborhoods. Outdoor sources of LAN estimated using low-dynamic range DMSP data had insufficient variability across urban neighborhoods to evaluate. While high-dynamic range DMSP offered much better variability, it was not significantly associated with urinary aMT6s.ConclusionsFuture health studies should utilize the high-dynamic range DMSP data and should consider other potential sources of circadian disruption associated with living in lower SES neighborhoods.
Highlights
There is accumulating evidence that circadian disruption, mediated by alterations in melatonin levels, may play an etiologic role in a wide variety of diseases
LAN values were universally higher among women living in urban compared to rural neighborhoods, with no overlap in values across rural and urban neighborhoods
The outdoor LAN variable was not selected through our stepwise model building approach, because it was of primary interest to us, we evaluated it separately in age-adjusted regression models and found it to have a very small inverse association with aMT6s that was not significant in either the full study population (β = −0.0028, se = 0.008, p = 0.73) or among those over age 55 (β = −0.0062, se = 0.012, p = 0.62)
Summary
There is accumulating evidence that circadian disruption, mediated by alterations in melatonin levels, may play an etiologic role in a wide variety of diseases. There is growing evidence that environmental light pollution may play an etiologic role in a variety of diseases, including depression, cardiovascular disease, and cancer [1,2,3,4,5,6,7,8,9,10] Such health effects are largely thought to be mediated via circadian disruption driven by alterations in melatonin production and secretion [11,12]. An endogenous hormone produced by the pineal gland, The primary objective of the current analyses was to evaluate the degree to which estimates of outdoor environmental light-at-night (LAN) predict levels of 6-sulfatoxymelatonin (aMT6s), the primary urinary metabolite of melatonin, among 303 California women. We evaluated whether selected anthropomorphic characteristics and behavioral and sociodemographic factors predict urinary concentrations of aMT6s
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