The presence of artificial light while sleeping may be a risk factor for overweight or obesity in women, according to study results published in JAMA Internal Medicine.
“There has been little investigation of the association between [artificial light at night] and obesity in humans,” Yong-Moon Mark Park, MD, PhD, of the epidemiology branch of the National Institute of Environmental Health Sciences in the NIH, and colleagues wrote. “Evidence has been mostly limited to studies of shift workers, for whom occupational light exposures are much higher than those experienced by the general population.”
To determine effect of artificial light at night (ALAN) on women in the general population, researchers collected data from the Sister Study, a national prospective cohort study that investigated environmental and genetic risk factors for breast cancer. The study enrolled 50,884 participants from the U.S. and Puerto Rico who were aged 35 to 75 years old, did not have breast cancer and had at least one sister who was diagnosed with breast cancer. Women responded to questionnaires every 2 to 3 years to provide information on changes in health status and risk factors.
In the questionnaires, women were asked about the types of ALAN they were typically exposed to while sleeping. During a baseline home visit, study personnel measured height, weight, and hip and waist circumference, and BMIs were calculated to determine the prevalence of obesity. Changes in BMI and waist circumference were recorded and evaluated to determine relation to ALAN.
The study included 43,722 women with a mean age of 55.4 years and mean 5.7 years of follow-up data. Those with more ALAN exposure had higher mean 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, 1-1.08), and waist-to-height ratio (PR = 1.07; 95% CI, 1.04-1.09) and were more likely to be Hispanic or black. Women who were exposed to ALAN were more likely to have less sleep, take a longer amount of time to fall asleep, wake up at night and take naps. Those exposed to ALAN were less likely to have consistent waking and bedtime sleeping patterns.
Researchers found that any ALAN exposure was associated with obesity (RR = 1.19; 95% CI, 1.06-1.34). Those who slept with a television or a light on in the room were more likely to gain 5 kg or more (RR = 1.17; 95% CI, 1.08-1.27), and more likely to experience a 10% or more increase in BMI (RR = 1.13; 95% CI, 1.02-1.26), incident overweight (RR = 1.22; 95% CI, 1.06-1.4) and incident obesity (RR = 1.33; 95% CI, 1.13-1.57) compared with those who were not exposed to ALAN.
Sensitivity analyses and multivariable analyses of factors such as sleep duration and quality, diet and physical activity supported the findings.
“Our findings provide evidence that exposure to ALAN while sleeping may be a risk factor for weight gain, overweight and obesity and suggest that lowering exposure to ALAN while sleeping might be a useful intervention for obesity prevention,” Park and colleagues wrote. – by Erin Michael
Disclosures: The authors report no relevant financial disclosures.