New research suggests that one night of sleep with just a moderate amount of light may have adverse effects on cardiovascular and metabolic health.
“I was surprised that even this fairly, I would say, small amount of light just getting through the eyes to the brain still had such notable effect,” says Dr. Phyllis Zee, senior author of the new study and director of the Center for Circadian and Sleep Medicine at Northwestern University.
For the study, all the participants spent their first night sleeping in a mostly dark room. The next night, half of them slept in a more illuminated room (the light was placed overhead).
Meanwhile, the researchers ran tests on the sleepers: they recorded their brainwaves, measured their heart rates and drew their blood every few hours, among other things. In the morning, they’d give both groups a big dose of sugar to see how well their systems responded to the spike.
…
Unlike those who spent both nights in the dark, the group exposed to the light had elevated heart rates throughout the night. They also had increased insulin resistance in the morning, meaning they had more trouble getting their blood sugar into a normal range.
