JUN 11, 2019 11:15 AM PDT

Do you sleep with a light or TV on? It may be causing weight gain.

WRITTEN BY: Tiffany Dazet

Are you exposed to any artificial light while sleeping? Exposure to artificial light at night could be a risk factor for obesity and weight gain, according to a study from scientists at the National Institute of Health. 

Because previous studies linked poor sleep to obesity and weight gain, the team was interested in researching the role that exposure to artificial light played in this association. In a press release regarding the study, co-author and chief of the Epidemiology Branch at the National Institute of Environmental Health Sciences (NIEHS) Dr. Dale Sandler stated that “although poor sleep by itself was associated with obesity and weight gain, it did not explain the associations between exposure to artificial light while sleeping and weight.”

This study, published online this week in JAMA Internal Medicine, was the first to discover an association between exposure to artificial light at night while sleeping and weight gain in women. Data from 43,722 women aged 35 to 74 from all U.S. States and Puerto Rico were used for this study. The participants had no history of cancer or cardiovascular disease; also, they were not night-shift workers, daytime sleepers, or pregnant. Participants were asked if they were exposed to artificial light at night classified as no light, a small nightlight, light outside their room, or light or television inside their bedroom. Baseline measurements of weight, height, waist and hip circumference, and body mass index were compared to measurements taken five years later.

The results showed that the use of a small nightlight was not associated with weight gain, and light outside the room was associated with a modest weight gain. However, women who slept with a light or television on in their bedroom were 17% more likely to have gained 5 kilograms (11 lb.) or more. Furthermore, there was a 22% chance of becoming overweight and a 33% percent chance of becoming obese.

Dr. Chandra Jackson, co-author and head of the NIEHS Social and Environmental Determinants of Health Equity Group, notes that exposure to light at night is more common in urban areas which may lead to racial or socioeconomic discrepancies in sleep health. Jackson states that because “humans are genetically adapted to a natural environment consisting of sunlight during the day and darkness at night, 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 authors note that there are other leading causes of obesity—such as unhealthy high-calorie diets or lack of exercise—but this may be one way that women can improve their health. Dr. Sandler stated that the United States is undergoing an obesity epidemic, and “it’s a very easy public health message to turn off the lights when you’re sleeping.”

Sources: CNN, NIEHS, JAMA
 

About the Author
  • Tiffany grew up in Southern California, where she attended San Diego State University. She graduated with a degree in Biology with a marine emphasis, thanks to her love of the ocean and wildlife. With 13 years of science writing under her belt, she now works as a freelance writer in the Pacific Northwest.
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