Light in Your Bedroom Is No Good for Your Health

WEDNESDAY, June 22, 2022 (HealthDay News) — Keeping your bedroom dark not only helps you get a good night’s sleep, but may significantly lower your odds of developing three major health problems, a new study suggests.

Older men and women who used night lights, or left their TV, smartphone or tablet on in the room were more likely to be obese, and have high blood pressure and diabetes, compared with adults who were not exposed to any light during the night.

“Maybe even a small amount of light at night is not so benign, it can be harmful,” said lead author Dr. Minjee Kim, an assistant professor of neurology at Northwestern University Feinberg School of Medicine’s Center for Circadian and Sleep Medicine in Chicago.

She cautioned, however, that the new study doesn’t prove that exposure to light during sleep causes any of these health conditions, only that there may be a link.

And, Kim said, there may be a biological explanation beyond disrupted sleep that ties light to an increased risk for obesity, diabetes and high blood pressure.

“It’s not natural to see those lights at night,” Kim said. “Light actually turns off some of the parts in the brain that tell our body it’s the daytime versus nighttime. So those signals are messed up in a way, because the circadian signal is weakened, and over time, that has implications for our health.”

So, she said, over time light may cause metabolic and heart diseases.

Kim and her colleagues looked at more than 550 participants in the Chicago Healthy Aging Study. The 63- to 84-year-olds wore devices that measured the amount of light in their bedrooms over a week.

Fewer than half had five hours in complete darkness as they slept, the study found. The others were exposed to some light even during the darkest five hours of the day — usually in the middle of their sleep at night.

The researchers said they didn’t know if obesity, diabetes and high blood pressure prompt people to sleep with a light on or if the light led to development of the conditions. But, they added, some people with foot numbness due to diabetes may want to use a night light to help prevent falls when they have to use the bathroom at night.