Association between outdoor light at night, sleep duration, and sleep quality in the US based-Health Professionals Follow-Up Study

Abstract

Background and aim Artificial illumination on the Earth’s surface has increased over time. Light plays a central role in regulating circadian rhythm, the body’s internal clock, mainly by inhibiting the production of the sleep promoting hormone melatonin. The increase in artificial light at night (LAN) has negative consequences for human health, as circadian disruption is a risk factor for weight gain, cardiovascular disease, and cancer. We evaluated whether exposure to outdoor LAN is associated with sleep duration and sleep quality in the US based-Health Professionals Follow-up Study (HPFS). Methods HPFS consists of 51,529 men enrolled in 1986 aged 40-75, our study is limited to men who reported a home address at baseline. We estimated participants’ LAN with 1 km2 resolution using data from the US Defense Meteorological Satellite Program’s Operational Linescan System to geocoded address histories. Participants self-reported their sleep duration in 1987, 2000, and 2008 and answered 5 questions regarding their sleep quality in 2004. We used multinomial logistic regression to estimate odds ratios and 95% confidence intervals adjusting for participants’ age, population density, and neighborhood SES (nSES). Results The mean level of LAN at baseline was 30.8 nW/cm2/sr. The distribution of age was similar, but population density and nSES differed across levels of LAN. An interquartile increase in LAN was associated with increased odds of sleeping ≤6 hours compared to 7-8 hours (OR: 1.20, 95%CI: 1.12,1.29), never feeling rested compared to most of the time (OR: 1.18, 95%CI: 1.05,1.34), and difficulty falling asleep (OR: 1.18, 95%CI: 1.02,1.36). Conclusion We found positive associations between LAN and measures of sleep duration and sleep quality in a large cohort of older adult men. This aligns with findings from other studies that living in areas of greater LAN has a negative impact on sleep health.