Sleeping with your lights and your television on has been linked with an increased risk of weight gain. It has been positively associated with gaining at least 5 kilograms, or 11 pounds, over a five-year period among women in a new study that was published in the medical journal JAMA Internal Medicine.
"There was a 17% chance of gaining the five kilograms -- after we adjusted for confounding factors," said Dale Sandler, a senior investigator at the National Institute of Environmental Health Sciences in North Carolina and senior author of the study.
She then said that there was a 22% chance of becoming overweight and a 33% chance of becoming obese.
"We are in the middle of an obesity epidemic in the United States and the things that we usually think about for obesity prevention are hard for people to do -- eat a better diet, get more exercise -- and we don't seem to be making a dent," Sandler said. "If these study findings are true and if they can be replicated then it's a very easy public health message to turn off the lights when you're sleeping."
The study involved analyzing data on 43,722 women, aged 35 to 74, in the United States. The data came from a nationwide cohort study called the Sister Study that enrolled women between 2003 and 2009. The data included information on each woman's sleeping habits, such as if she slept with a small nightlight or television on, and her body mass index.
BMI or body mass index is a calculation derived from a person' weight and height. The women's sleeping habits were placed into four different categories: no light, small nightlight in the room, the light outside of the room and with the light or television in the room. Women who reported more than one type of artificial light were categorized at the highest level of exposure. Women who slept with a mask on or with no light while sleeping were classified as experiencing no artificial light exposure.
The researchers took a close look at each of their sleeping habits and their weight and obesity risk over a five-year period. Among the women, the researchers found that sleeping with a television or light on in the room was associated with gaining at least 5 kilograms or more, a BMI increase of at least 10% and a higher risk of being overweight or obese, compared with being exposed to no artificial light during sleep.
"There was a dose response, in that the lighter in the room the stronger the association," Sandler said.
The new study also highlights that "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.
"As the authors mention, you can't point directly to causality between bedroom light exposure at night for a sleeping individual and weight gain, but I think this is definitely a step in that direction," he said. "It indicates that we need to respect our sleep and respecting our sleep means making a sleep environment devoid of any type of light ideally."
