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Sleeping with lights on linked to weight gain in women

Cover Media logo Cover Media 6 days ago
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Sleeping with a television or light on in a bedroom may be a risk factor for gaining weight or developing obesity, researchers report.

Scientists at the U.S. National Institutes of Health have analysed data from over 43,500 women in the Sister Study, which examines risk factors for breast cancer and other diseases, with the participants aged between 35-74 years.

The study questionnaire asked whether the women slept with no light, a small nightlight, light outside of the room, or a light or television on in the room, and accordingly, they found an association between any exposure to artificial light at night while sleeping and weight gain in women.

Co-author Dr. Chandra Jackson, head of the NIEHS Social and Environmental Determinants of Health Equity Group, noted that people who live in urban environments may also be affected, as street lights, neon signs and other light sources can suppress the sleep hormone melatonin and the natural 24-hour light-dark cycle of circadian rhythms.

"Humans are genetically adapted to a natural environment consisting of sunlight during the day and darkness at night," she said. "Exposure to artificial light at night may alter hormones and other biological processes in ways that raise the risk of health conditions like obesity."

The results varied with the level of artificial light at night exposure, as using a small nightlight was not linked to weight gain, while women who slept with a light or television on were 17 per cent more likely to have gained five kilograms, approximately 11 pounds, or more, over the follow-up period. Yet, the association with having light coming from outside the room was more modest.

The study authors acknowledge that other factors could explain the connections between artificial light at night and weight gain. However, their findings did not change when analyses controlled for characteristics that may be associated with exposure to light at night.

"Unhealthy high-calorie diet and sedentary behaviours have been the most commonly cited factors to explain the continuing rise in obesity," Dr. Yong-Moon Park added. "This study highlights the importance of artificial light at night and gives women who sleep with lights or the television on a way to improve their health."

Full study results have been published in JAMA Internal Medicine.

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