Keeping a lot of light on while you snooze such as from a television or bright nightlight, has been linked with an increased risk of weight gain and obesity.
Specifically, sleeping with a television or light on in the room was positively associated with gaining 5kg, or 11 pounds, over a five-year period among women in a new study published recently.
“There was a 17% chance of gaining the 5kg 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.
In addition, there was a 22% chance of becoming overweight and a 33% chance of becoming obese, she added.
Obesity means having too much body fat and overweight means weighing too much. Both overweight and obesity are based on your body mass index but “obese” generally means having a much higher BMI.
“We are in the middle of an obesity epidemic and the things that we usually think about obesity prevention are hard for people to do. That is, to eat a better diet, get more exercise and we don’t see, 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 US.
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 and her body mass index.
Body mass index, a calculation derived from a person’s weight and height, can be used as a screening tool for body fatness and obesity risk. A normal or healthy BMI is typically considered between 18.5 and 24.9. A BMI of 30 and higher is considered to e obese.
The women’s self-reported sleeping habits were put into four categories: no light, small nightlight in the room, light outside of the room, and 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 reported no light while sleeping were classified as experiencing no artificial light exposure.
The researchers took a close look at each woman’s sleeping habits and her weight and obesity risk over a five-year period.
Among the women, the researchers found that sleeping with a light int eh room was associated with gaining 5kg 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.
Like every research, there were critics. “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.” Said Dr. Nathaniel Watson, a professor of neurology and director of the Harborview Sleep Clinic at the University of Washington in Seattle.
