Do You Sleep With the Lights On?

Science Fields

A recent study from Northwestern University suggests that light exposure during sleep increases the risk for cardiometabolic disease. 

For this study, a total of 20 participants were randomly assigned to either one of two conditions: In one condition, the participants slept in a dimly lit (< 3 lx) room followed by one night of sleep with overhead room lighting (100 lx); in the other condition, half of the participants slept in a dimly lit room for two consecutive nights. 

The study results showed that participants who slept with the overhead light spent less time in slow wave and rapid eye movement (REM) sleep compared to those who slept in a dimly lit room. 

The researchers report that one night of moderate (100 lx) light exposure during sleep increases heart rate and decreases heart rate variability at night. The study also suggests that there is an association between night-time light exposure and insulin resistance the next morning. Insulin resistance occurs when cells do not respond to insulin like they should. When the body fails to properly use glucose for energy, the pancreas produces more insulin which then further exacerbates the problem. 

According to Dr. Phyllis Zee, chief of sleep medicine at Northwestern University Feinberg School of Medicine, “The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome.”

To make sure your room is dark enough, Dr. Zee recommends black out shades or eye masks to avoid exposure to outdoor lighting. If you need to have a light on, make sure that it is dimly lit and try to avoid white/blue light and use amber, red/orange light on your screen instead.



  • 1. Mason, I. C.,Grimaldi, D., Reid, K. J., Warlick, C. D., Malkani, R. G., Abbott, S. M., & Zee, P. C. (2022). Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences,119 (12) DOI: 10.1073/pnas.2113290119
  • 2. https://www.sciencedaily.com/releases/2022/03/220314154355.htm