Sleep at night with artificial light associated with weight gain in women

Press release

Monday, June 10, 2019

The elimination of light during sleep could reduce obesity.

According to scientists at the National Institutes of Health, sleeping with a TV or a lit light in the room can be a risk factor for weight gain or obesity. The research, published online in JAMA Internal Medicine on June 10, is the first to establish an association between all nighttime artificial light exposure during sleep and weight gain in women. The results suggest that cutting off lights at bedtime could reduce women's chances of becoming obese.

The research team used data from a questionnaire of 43,722 women in Sister Study, a cohort study focusing on risk factors for breast cancer and other diseases. Participants, aged 35 to 74, had no history of cancer or cardiovascular disease and were not shiftworkers, daytime sleepers, or pregnant women at the start of the study. The study questionnaire asked if women slept without light, with a small night light, an outside light, or a light or television in the room.

Scientists used basic measurements of weight, height, height and hips, as well as body mass indexes, as well as self-reported information on weight at baseline and follow-up five years later. Using this information, scientists were able to study obesity and weight gain in women exposed to artificial light at night, as well as in women who reported sleeping in dark rooms.

The results varied with the artificial light level during a nocturnal exposure. For example, the use of a small night light was not associated with weight gain, while women who slept with a light or on television were 17% more likely to have taken 5 kilograms, about 11 pounds or more during the follow-up period. The association of light coming from outside the room was more modest.

In addition, scientists wondered whether to take enough rest time in the results.

"Although lack of sleep is associated with obesity and weight gain, it does not explain the links between exposure to artificial light during sleep and weight," he said. said corresponding author Dale Sandler, Ph.D., head of the Epidemiology Division of the National Institute of Environmental Health Sciences (NIEHS), belonging to the NIH.

Co-author Chandra Jackson, Ph.D., leader of the NIEHS group on the social and environmental determinants of health equity, looks at racial disparities in sleep health. She notes that for many of those living in urban areas, night light is more common and should be taken into account. Streetlamps, neon signs in stores, and other light sources can suppress melatonin, a sleep hormone, and the natural day-night cycle of circadian rhythms that lasts 24 hours.

"Humans are genetically adapted to a natural environment including sunlight during the day and darkness at night," Jackson said. "Nighttime exposure to artificial light can alter hormones and other biological processes, increasing the risk of diseases such as obesity.

The authors recognize that other confounding factors may explain associations between artificial night light and weight gain. However, their results did not change when the analyzes controlled the characteristics that may be associated with light exposure at night. These factors included age, having an older spouse or children at home, race, socio-economic status, calories consumed, and physical activity. In addition, the study did not include men.

Lead author Yong-Moon (Mark) Park, M.D., Ph.D., is a postdoctoral fellow of the Sandler Group. He said the research suggests a viable public health strategy to reduce the incidence of obesity in women.

"An unhealthy low calorie diet and sedentary behaviors have been the most commonly cited factors to explain the ongoing increase in obesity," said Dr. Park. "This study highlights the importance of artificial light at night and gives women who sleep with light or on television a way to improve their health."

This press release describes basic research. Basic research increases our understanding of human behavior and biology, which is fundamental to advancing new and improved methods of disease prevention, diagnosis and treatment. Science is an unpredictable and progressive process – every breakthrough in research builds on past discoveries, often unexpectedly. Most clinical progress would not be possible without the knowledge of basic fundamental research.

Grant number: Z01ES440055

About the National Institute of Environmental Health Sciences (NIEHS): NIEHS supports research to understand the effects of the environment on human health and is part of the National Institutes of Health. For more information on NIEHS or on topics related to environmental health, visit www.niehs.nih.gov or subscribe to a list of news.

About the National Institutes of Health (NIH):
The NIH, the country's medical research agency, has 27 institutes and centers and is part of the US Department of Health and Human Services. NIH is the lead federal agency that leads and supports basic, clinical and translational medical research. She studies causes, treatments and cures for common and rare diseases. For more information on NIH and its programs, visit www.nih.gov.

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