New Study Reveals 3 Surprising Health Effects Of Light Exposure During Sleep

For this study, researchers wanted to find out how exposure to light during sleep would affect participants. They had 20 young adults take part in the study that lasted for two nights.

One group of 10 participants slept in a room with dim light on the first night, then with overhead lighting on the second night. The other half of the participants had two nights of dim light while they slept.

Compared to the participants who slept in dim lighting, those who slept with overhead lighting spent more time in stage two sleep and less in REM and slow-wave sleep—which is essential for rest and recovery. The group with light disrupting their sleep also experienced higher insulin levels in their blood and less insulin sensitivity in the morning.

Additionally, compared to the dim lighting group, those who slept with overhead lighting experienced a higher heart rate and lower heart rate variability, which the study authors believe is related to the nervous system. As study co-author Daniela Grimaldi, Ph.D., explains in a news release, "We showed your heart rate increases when you sleep in a moderately lit room. Even though you are asleep, your autonomic nervous system is activated." She notes that typically, heart rate is meant to be lower at night and higher during the day.

And as senior study author Phyllis Zee, Ph.D., adds, "It's important for people to avoid or minimize the amount of light exposure during sleep. These findings are important, particularly for those living in modern societies where exposure to indoor and outdoor nighttime light is increasingly widespread."