Your bedroom is probably not dark enough

In 2022, researchers at Northwestern put healthy young adults to sleep in two conditions: a dim room at 3 lux, and a moderately lit room at 100 lux. Roughly the difference between a properly dark bedroom and one with a hallway light on.

One night in the lit room was enough. Heart rate went up. The sympathetic nervous system — the one that is supposed to stand down at night — stayed switched on. The next morning, those participants showed measurably higher insulin resistance.

One night.

The test the lead researcher gives is simple: if you can see things in your room really well, it is too light.

Among the fixes the team recommends: blackout blinds, moving the bed away from the window, and an eye mask.