The new study published in the journal Sleep, focused on seniors who "already are at higher risk for diabetes and cardiovascular disease," said coauthor Dr. Minjee Kim, an assistant professor of neurology at Northwestern University Feinberg School of Medicine, in a statement.
"We wanted to see if there was a difference in frequencies of these diseases related to light exposure at night," Kim said.
Instead of pulling people into a sleep lab, the new study used a real-world setting. Researchers gave 552 men and women between the ages of 63 and 84 an actigraph, a small device worn like a wristwatch that measures sleep cycles, average movement and light exposure.
"We're actually measuring the amount of light the person is exposed to with a sensor on their body and comparing that to their sleep and wake activity over a 24-hour period," Zee said. "What I think is different and notable in our study is that we have really objective data with this method."
Zee and her team said they were surprised to find that fewer than half of the men and women in the study consistently slept in darkness for at least five hours each day.
"More than 53% or so had some light during the night in the room," she said. "In a secondary analysis, we found those who had higher amounts of light at night were also the most likely to have diabetes, obesity or hypertension."
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