Exposure to artificial light at night while sleeping may be a risk factor for weight gain and development of obesity in women, according to results published in JAMA Internal Medicine.

The study included 43,722 women age 35 to 74 years enrolled in the Sister Study in all United States states and Puerto Rico from July 2003 through March 2009. Participants were followed until August 14, 2015. Participants had no history of cancer or cardiovascular disease and were not shift workers, daytime sleepers, or pregnant at baseline.

Upon enrollment, participants reported their exposure to artificial light at night while sleeping, categorized as no light, small nightlight in the room, light outside the room, and light or television in the room.


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The researchers measured general obesity (body mass index [BMI] ≥30.0) and central obesity (waist circumference ≥88 cm, waist-to-hip ratio ≥0.85, or waist-to-height ratio ≥0.5). They compared self-reported BMI at enrollment with self-reported BMI at follow-up to evaluate incident overweight and obesity.

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After adjusting for confounding factors, the results indicated that any exposure to artificial light at night while sleeping was positively associated with a higher prevalence of obesity at baseline, as measured by BMI (prevalence ratio [PR], 1.03; 95% CI, 1.02-1.03), waist circumference (PR, 1.12; 95% CI, 1.09-1.16), waist-to-hip ratio (PR, 1.04; 95% CI, 1.00-1.08), and waist-to-height ratio (PR, 1.07; 95% CI, 1.04-1.09) (P <.001 for all). Any artificial light exposure while sleeping was also associated with incident obesity (risk ratio [RR], 1.19; 95% CI, 1.06-1.34).

Sleeping with a television or light on in the room was associated with gaining 5 kg or more (RR, 1.17; 95% CI, 1.08-1.27; P <.001 for trend), a BMI increase of 10% or more (RR, 1.13; 95% CI, 1.02-1.26; P =.04 for trend), incident overweight (RR, 1.22; 95% CI, 1.06-1.40; P =.03 for trend), and incident obesity (RR, 1.33; 95% CI, 1.13-1.57; P <.001 for trend) compared with no artificial light at night.

“Our findings provide evidence that exposure to [artificial light at night] while sleeping may be a risk factor for weight gain, overweight, and obesity and suggest that lowering exposure to [artificial light at night] while sleeping might be a useful intervention for obesity prevention,” the researchers wrote.

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Reference

Park YM, White AJ, Jackson CL, Weinberg CR, Sandler DP. Association of exposure to artificial light at night while sleeping with risk of obesity in women [published online June 10, 2019]. JAMA Intern Med. doi:10.1001/jamainternmed.2019.0571