Bedroom light at night might cause women weight gain

Grant Boone
June 13, 2019

The new study further highlights "the common recommendation that we make for people to remove TVs and other technology out of the bedroom environment to facilitate healthy sleep", said Dr. Nathaniel Watson, a professor of neurology and director of the Harborview Sleep Clinic at the University of Washington in Seattle, who was not involved in the study.

For the study, Park's team relied on self-reported data from almost 44,000 women, aged 35 to 74.

Bottom Line: Exposure to artificial light at night, especially sleeping with a light or television on in the room, was associated with increased risk of weight gain and overweight and obesity among a large group of women studied.

Eliminating lights and screens from bedrooms could be an important step in fighting the obesity crisis, the researchers believe.

Published Monday in JAMA Internal Medicine, the research by a team at the National Institutes of Health is the first to find an association between artificial light exposure and weight gain in women.

The researchers found that women who slept with a slept with a light or television on in the same room were 17% more likely to gain 5kg or more over the next five years.

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Exposure to blue light at night messes with your Circadian Rhythm aka your body clock. However, most of this research was conducted in night-shift workers who are exposed to high levels of light at night; these results may not apply to the general population.

"Public health strategies to decrease obesity might consider interventions aimed at reducing ALAN while sleeping", wrote Dale Sandler and Yong-Moon Mark Park of the National Institute of Environmental Health Sciences in North Carolina and coauthors.

Among women who weren't obese at the study's, those who reported exposure to any light at night were about 20% more likely to become obese during the study, compared with those who didn't report exposure to light at night.

"Humans are genetically adapted to a natural environment consisting of sunlight during the day and darkness at night", says co-author Chandra Jackson, Ph.D. "It seems reasonable to advise people not to sleep with lights on", Park and Sandler said.

"These results suggest that exposure to [artificial light at night] while sleeping may be a risk factor for weight gain and development of overweight or obesity", the researchers conclude. However, their findings did not change when analyses controlled for characteristics that may be associated with exposure to light at night. Most clinical advances would not be possible without the knowledge of fundamental basic research.

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