Light in Bedroom Linked to Hypertension, Diabetes
By Chauncey Crandall, M.D.
Keeping your bedroom dark may significantly lower your odds of developing major health problems.
In a recent study, 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 to adults who were not exposed to any light during the night.
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"Maybe even a small amount of light at night can be harmful," said lead author Minjee Kim, M.D., assistant professor of neurology at Northwestern University Feinberg School of Medicine's Center for Circadian and Sleep Medicine in Chicago.
"Light actually turns off some of the parts in the brain that tell our body it's the daytime versus nighttime. The circadian signal is weakened, and over time, that has implications for our health."
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.