Exposure to artificial light at night (ALAN) while sleeping may increase risk for weight gain and development of obesity in women, according to research results published in JAMA Internal Medicine.

Investigators conducted a baseline and prospective analysis to assess whether exposure to ALAN while sleeping is associated with the prevalence and risk for obesity. Women between ages 35 and 74 years with no history of cancer or cardiovascular disease who were not shift workers, daytime sleepers, or pregnant at baseline were eligible to participate in the investigation. Exposures to light included no light, small nightlight in the room, light outside the room, and light or television in the room.

Investigators found that of 43,722 women (mean age, 55.4 years) included in the study, those with greater exposure to ALAN had a higher average body mass index, waist circumference, waist-to-hip ratio, weight-to-height ratio, and were more likely to be non-Hispanic black.

In addition, these women were less likely to have regulated waking and bedtime patterns and were more likely to have less sleep, wake up at night, take naps, and take longer to fall asleep.

Compared with no light exposure, sleeping with a television or light on in the room was linked to a weight gain of ≥5 kg (relative risk [RR], 1.17), a body mass index increase of ≥10% (RR, 1.13), incident overweight (RR, 1.22), and incident obesity (RR, 1.33).

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“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,” the authors concluded. “However, ALAN exposure while sleeping represents a constellation of socioeconomic disadvantage measures and unhealthy lifestyle behaviors, all of which could contribute to weight gain and obesity.”


Park, Y-MM, 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