WEST COLUMBIA, S.C. — How many times have you fallen asleep with the lights or television on or even stayed up late to use your computer right before going to bed? 

According to a  2014 national consumer study, watching TV before bed is a common nightly ritual but recent research lead by National Institutes of Health  suggests that could put you at risk for obesity.

The Centers for Disease Control reports that obesity is common and serious. It affects about 93.3 million of US adults and increases risks of preventable, premature death caused by  heart disease, stroke, Type 2 diabetes and certain types of cancer.

The National Institutes of Health (NIH) study authors note that obesity prevention including  eating a better diet and  getting more exercise can be difficult for people. This study could send public health message to turn off the lights when you’re sleeping.

It has been proven that adults need on average seven hours of quality sleep for our brain and body to restore itself and to function optimally. But to date the association between exposure to artificial light at night (ALAN) while sleeping and obesity had been unclear.

The scientists did not focus on how artificial light is contributing to the findings  but it does shows evidence suggesting that that light may disrupt sleep enough to change levels of appetite-regulating hormones or cause daytime sleepiness that reduces physical activity  could lead to health risks.

"Humans are genetically adapted to a natural environment consisting of sunlight during the day and darkness at night," said study Co-author Chandra Jackson, Ph.D., head of the NIEHS Social and Environmental Determinants of Health Equity Group. "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 research team used questionnaire data from over 40,0000 women enrolled in an ongoing study seeking clues to causes of breast cancer. The analysis focused on data on sleep, light exposure and weight gain during the study, but not on breast cancer. Results were published in JAMA Internal Medicine.  https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/2735446 

The participants, aged 35-74 years ( average age of 55 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.

Corresponding author Dale Sandler, Ph.D., chief of the Epidemiology Branch at the National Institute of Environmental Health Sciences (NIEHS), part of NIH aid it's likely similar results would be found in men.

The study authors also noted that the added weight wasn't from things like snacking at night, because the analysis accounted for other variables that could have led to weight gain such as diet, physical activity and sleep duration.  

60% of Americans watch TV right before falling asleep.

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

"Unhealthy high-calorie diet and sedentary behaviors have been the most commonly cited factors to explain the continuing rise in obesity," Park said. "This study highlights the importance of artificial light at night and gives women who sleep with lights or the television on a way to improve their health."