Study: Closing the Blinds During Sleep Protects Health

A new Northwestern Medicine study found that exposure to the slightest ambient lighting during nighttime sleep harms cardiovascular function during sleep and increases insulin resistance the following morning compared to sleeping in a dimly lit room.

“The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome,” said senior study author Phyllis Zee, MD, PhD, chief of sleep medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician, in a press release. “It’s important for people to avoid or minimize the amount of light exposure during sleep.”

Zee added that the results indicate that a similar effect is also present when exposure to light occurs during nighttime sleep.

“We showed your heart rate increases when you sleep in a moderately lit room,” said co-first author Daniela Grimaldi, MD, research assistant professor of neurology at Northwestern, in a press release. “Even though you are asleep, your autonomic nervous system is activated. That’s bad. Usually, your heart rate together with other cardiovascular parameters are lower at night and higher during the day.”

The study authors found that insulin resistance occurred the morning after people slept in a light room, which means that the cells in the muscles, fat, and liver do not respond well to insulin and cannot use glucose from blood for energy.

“Now we are showing a mechanism that might be fundamental to explain why this happens. We show it’s affecting your ability to regulate glucose,” Zee said in a press release.

Artificial light exposure at night during sleep is very common, either from indoor light emitting devices or from sources outside the home, specifically in large urban areas. Additionally, a significant proportion of individuals sleep with a bedside lamp on, with a light on in the bedroom, and/or the television on.

“In addition to sleep, nutrition and exercise, light exposure during the daytime is an important factor for health, but during the night we show that even modest intensity of light can impair measures of heart and endocrine health,” said co-first author Ivy Mason, MD, who at the time of the study was post-doctoral fellow at Northwestern and now is a research fellow at Harvard Medical School, in a press release.

REFERENCE

Close the blinds during sleep to protect your health. Northwestern Now. March 14, 2022. Accessed April 18, 2022. https://news.northwestern.edu/stories/2022/03/close-the-blinds-during-sleep-to-protect-your-health/#:~:text=Exposure%20to%20even%20moderate%20ambient,a%20new%20Northwestern%20Medicine%20study