Why You Should Sleep with the Lights Off

By Christine Macahilig
February 25, 2023

Reviewed by Susan Ko, Ph.D.

Creating the optimal bedtime routine is important for getting a good night’s sleep. Eliminating distractions or queuing up your playlist are all ways to gently send you off to dreamland. But there’s another thing you should make a part of your regular nightly ritual: turning out the lights. Being exposed to light, whether from lightbulbs or the television, while sleeping may impair heart health and increase insulin resistance, suggests one study.

In the study, conducted by researchers at Northwestern University Feinberg School of Medicine, 20 young adults were split into two groups. Half slept with dim lighting one night and overhead lighting the second night; the other half slept in dim lighting for consecutive nights. The results showed that participants who were exposed to light while sleeping experienced an increase in heart rate and higher blood sugar levels than those who only slept in dim lighting.