WEDNESDAY, June 22, 2022 (HealthDay News) — Keeping your bedroom dark not only helps you get a good night’s sleep, but can also significantly reduce your risk of developing three major health conditions, according to a new study.

Older men and women who used nightlights or left their TVs, smartphones or tablets on in the room were more likely to be obese and to have high blood pressure and diabetes, compared to adults who did not. were exposed to no light at night.

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

She cautioned, however, that the new study does not prove that exposure to light during sleep causes any of these health problems, only that there may be a link.

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

“It’s not natural to see these lights at night,” Kim said. “The light actually turns off some of the parts of the brain that tell our bodies whether it’s day or night. So those signals are disrupted in some way because the circadian signal is weakened and over time that has implications for our health.”

So, she said, over time, the light can cause metabolic and heart disease.

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 room for a week.

Less than half spent five hours in complete darkness while they slept, according to the study. The others were exposed to light even during the darkest five hours of the day – usually in the middle of their sleep at night.

The researchers said they don’t know if obesity, diabetes and high blood pressure cause people to sleep with a light on or if the light leads to the conditions developing. But, they added, some people with numbness in their feet due to diabetes may want to use a nightlight to help prevent falls when they have to use the bathroom at night.

Emerson Wickwire, professor and section chief of sleep medicine at the University of Maryland School of Medicine, was not part of the study, but reviewed the results. He said the findings add to a growing body of scientific evidence showing the importance of the body’s circadian clock and sleep for overall health, especially in older people.

“What these data show is that exposure to light at night increases the risks of two of the most common and costly chronic diseases in the United States and around the world – obesity and diabetes – as well as hypertension, a major cardiovascular risk factor,” Wickwire said. “While this study deserves careful follow-up in future studies, these are exciting results.”

Several factors may explain the worsening health effects of nighttime light exposure, Wickwire said.

“First, light at night could worsen health by deregulating the circadian clock,” he said. “In addition to sleep, circadian health is vital for disease prevention and optimal performance.”

Second, Wickwire noted that light is a powerful melatonin suppressor.

“Melatonin, also called the hormone of darkness, is associated with multiple health properties, including anti-inflammatory and antioxidant properties. Nighttime light reduces melatonin,” Wickwire said.

In addition to increasing physiological stress, he said, nighttime light can also be a marker of poor overall health, as people awake at night may engage in other risky behaviors.

To get the full benefits of sleep, Wickwire has this advice: “Create a sacred space for sleep,” he says. “Your bedroom environment should be cool, dark, calm and uncluttered.”

Kim’s team also has tips for keeping bedroom lighting to a minimum:

  • Don’t turn on the lights. If you need to have a light on for your safety, turn it on near the ground.
  • The color of the light is important. Amber or red/orange light is less stimulating for the brain. Do not use white or blue light and keep it away from the bed.
  • If you can’t control outside light, use blackout blinds or wear an eye mask.
  • Place your bed so that outside light does not shine on your face.

The results were published June 22 in the journal Sleep.

More information

For more on a good night’s sleep, check out the US National Institute on Aging.

SOURCES: Minjee Kim, MD, assistant professor, neurology, Center for Circadian and Sleep Medicine, Northwestern University Feinberg School of Medicine, Chicago; Emerson Wickwire, PhD, professor and section chief, sleep medicine, University of Maryland School of Medicine, Baltimore; SleepJune 22, 2022