How dim should your lights be before bed?

On Huberman Lab (October 2021), Samer Hattar, who leads the section on light and circadian rhythms at the US National Institute of Mental Health, told host Andrew Huberman how he lights his own home at night. Friends who study light had teased him that they could break a leg in his house. In that conversation, he offered everyone else a gentler version, and he said you have to measure it for yourself.

I call it the minimum amount of light you require to see comfortably.

Samer Hattar, Huberman Lab, 2021

As little light as you need, not darkness

Hattar studies how light reaching the eye tells the body clock what time it is. Light in the morning helps set your clock. Bright light in the evening tells it the day is still going, which nudges your sleepiness later. So his experiment is simple: in the evening, dim the lights as far as you can while still seeing comfortably, and stop there. He admits his own home is an extreme case, and that he and his wife both happen to see well in dim light.

He was just as clear about the other end. He doesn't aim for a pitch-black house in the evening, and he dislikes complete darkness. For a light you keep on at night, he suggests something very dim and reddish, which he says has very little effect on the clock. The target is the edge where you can still see comfortably, not the point where you're feeling for the furniture.

What the research says

A 2022 consensus of light researchers put numbers on the same idea. For healthy adults, it recommends that evening light at the eye stay at or below about 10 lux of a measure called melanopic EDI, starting at least three hours before bedtime, and that the bedroom be as dark as possible while you sleep. Few people own a light meter, and these are directions from lab studies rather than exact targets for your living room. Hattar's comfort test turns them into something you can feel.

One caution matters more than any number: keep enough light to move around safely, especially on stairs and on the way to the bathroom at night. A fall costs far more than a little extra light.

How this fits the Better Sleep program

In the 1h Protocol for Better Sleep, the chapter "Tonight, hour by hour" sets a dim-down time counted back from your own lights-out, alongside your caffeine cut-off, runway and morning light. You then choose a cue that does the remembering for you, such as the ceiling light going off or something you already do, like clearing up after dinner; a version of Hattar's lamp test appears on that screen. If your answers point to the Mistimed pattern, a body clock running late, light and timing are where you start. The first chapter is free: find your sleep pattern.

Source: Huberman Lab, Dr. Samer Hattar: Timing Light, Food, & Exercise for Better Sleep, Energy & Mood, 25 Oct 2021 Research: Brown et al., indoor light exposure recommendations for healthy adults (2022)