Sleeping with a screen on can lead to female obesity

The researchers considered several other compounding factors, like sleep deprivation, which could have played a role in the association between artificial light exposure at night and weight gain.

The analysis, published Monday by the National Institute of Health, used questionnaire data from 43,722 women between the ages of 35 and 74.

The results suggest that cutting off lights at bedtime could reduce women's chances of becoming obese.

Ashton suggests that women create a prime sleeping environment for themselves by using tools like eye masks and blackout shades or drapes. "We know from experimental studies in people that light at night affects our metabolism in ways that are consistent with increased risk of metabolic syndrome", von Schantz said. "It is a medical necessity on par with our food and our fitness".

At their first check-in, the women were asked to report on their light exposure while they slept - whether they kept lights on in their rooms or in other rooms, whether light shone in through the windows, whether they slept with a TV on, and even from low-light sources such as clock radios.

The study researchers found that women who reported exposure to light at night while sleeping were more likely to gain weight and become obese over almost six years, compared with women who were not exposed to light at night.

"While sleeping with a small night light was not associated with putting on pounds, researchers found that women who slept with a room light or television on were 17 percent more likely to have gained approximately 11 pounds or more during the study's follow-up period".

"Our findings. suggest that lowering exposure to [artificial night at light] while sleeping may be a useful intervention for obesity prevention", researchers said.

Sandler said she is confident 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. Also, the study did not include men. He is a postdoctoral fellow at the US National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina.

Respondents reported exposure to artificial light at night (ALAN) from televisions, smart phones, computers, e-readers and tablets, which emit a short wavelength-enriched light or "blue light" that previous research has linked to melatonin suppression and circadian disruption.

Lead author of the study, Yong-Moon Park, Ph.D., said, "Unhealthy high-calorie diet and sedentary behaviors have been the most commonly cited factors to explain the continuing rise in obesity". NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases.