Racial/ethnic and sex differences in the association between light at night and actigraphy-measured sleep duration in adults: NHANES 2011-2014.

Objective: Historically minoritized individuals experience greater exposure to light at night, yet it is unclear whether the association between light at night and sleep duration vary by race/ethnicity or sex. We examined the association between light at night and sleep duration by race/ethnicity and sex.

Methods: Participants (N = 6089, mean age=49.5, 52% women, 13% Asian, 27% Black, 14% Mexican, 46% White) in the 2011-2014 National Health and Nutrition Examination Survey underwent 9-day of actigraphy. Light at night was defined as light exposure within the 5-hour activity nadir (L5). Sleep duration within a 24-hour period was analyzed as short (<7 hours) or long (>9 hours) compared to recommended (≥7 and <9 hours). Poisson models were fit to estimate the association between light at night and sleep duration after adjustment for covariates.

Results: Light at night was most common among Black participants, who also had the shortest sleep duration. Overall, light at night was associated with 80% higher prevalence of short sleep duration [1.80 (1.49, 2.18)]. Compared to no-light at night, low and high light at night were associated with higher prevalence of short sleep duration, [1.61 (1.31, 1.98) and 2.01 (1.66, 2.44), respectively]. Associations varied by race/ethnicity and sex. Light at night was associated with shorter sleep duration in Black, Mexican and White females and Mexican and White males only. Black males exposed to light at night vs. no-light at night had lower prevalence of long sleep duration. There were no associations between light at night and sleep duration among Asian participants.

Conclusion: Light at night was associated with shorter sleep duration, particularly among females. Targeting light exposure may help to improve sleep duration.