WASHINGTON (Dispatches) -- Sleeping with a television or light on in the room may be a risk factor for gaining weight or developing obesity, according to scientists.
The research team at the National Institutes of Health, Maryland used questionnaire data from 43,722 women in the Sister Study, a cohort study that examines risk factors for breast cancer and other diseases. The participants, aged 35-74 years, had no history of cancer or cardiovascular disease and were not shift workers, daytime sleepers, or pregnant when the study began. 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.
The scientists used weight, height, waist and hip circumference, and body mass index measurements taken at baseline, as well as self-reported information on weight at baseline and follow-up five years later. Using this information, the scientists were able to study obesity and weight gain in women exposed to artificial light at night with women who reported sleeping in dark rooms.
The results varied with the level of artificial light at night exposure. For example, using a small nightlight was not associated with weight gain, whereas women who slept with a light or television on were 17% more likely to have gained 5 kilograms, approximately 11 pounds, or more over the follow-up period. The association with having light coming from outside the room was more modest.