For women, artificial light at night may lead to packed-on pounds

Bethesda, MD — Turning off the lights and TV at bedtime may reduce a woman’s risk of gaining weight, according to the results of a recent study from the National Institutes of Health.

To come to this conclusion, researchers examined data from nearly 44,000 women who participated in The Sister Study. Participants, who ranged in age from 35 to 74, were asked about whether they slept at night with no light, a small nightlight, light outside the room, or a light or TV on in the room. They had no history of cancer or cardiovascular disease; and were not shift workers, daytime sleepers or pregnant when the study began.

The researchers took weight, height, waist and hip circumference, body mass index, and other measurements at baseline, then again during a five-year follow-up. They determined that women who slept with a light (not including small nightlights) or TV on were 17% more likely to have gained about 11 pounds or more during the follow-up.

The researchers recommend limiting or eliminating artificial light while sleeping to help prevent obesity and increase sleep duration.

“Unhealthy high-calorie diet and sedentary behaviors have been the most commonly cited factors to explain the continuing rise in obesity,” Yong-Moon Park, lead study author and a postdoctoral fellow at the National Institute of Environmental Health Sciences, said in a June 10 press release. “This study highlights the importance of artificial light at night and gives women who sleep with lights on or the television on a way to improve their health.”

The study was published online June 10 in the journal JAMA Internal Medicine.