Evening Light and Sleep: How Dim Should Your Evenings Be?

Evening light, including ordinary room light and screens, delays the body clock and suppresses melatonin, and in lab studies it can lengthen the time it takes to fall asleep. A 2022 expert consensus recommends keeping light at eye level to no more than 10 lux melanopic EDI from at least 3 hours before bedtime and no more than 1 lux in the bedroom. Total brightness matters most; color settings and blue-blocking glasses help less reliably.

This page summarizes research for general information. It is not medical advice. If you have persistent sleep problems, see a clinician rather than relying on light changes alone.

How evening light affects sleep

Light reaching melanopsin-containing cells in the retina signals the brain’s master clock. In the evening, that signal delays the clock and suppresses melatonin, the hormone that rises as night approaches. The light and circadian rhythm guide explains why timing decides the direction of the shift.

The key finding from lab studies is how little light it takes:

The 2019 study concluded that “the circadian system is highly sensitive to evening light at typical indoor levels.” It also found large differences between people: the light level that produced half the maximum response ranged from 6 lux in the most sensitive participant to 350 lux in the least.

Does it change sleep itself?

Melatonin is a marker, not sleep. The sleep effects are smaller and less consistent.

• Pooled lab studies: a 2022 meta-analysis of 12 sleep-lab studies (Cajochen et al.) found that evening light lengthened sleep onset and lowered sleep efficiency on average, but the confidence intervals crossed zero. The clearest dose-response appeared when light was expressed as melanopic EDI, in the range of 100–1,000 lux.
• E-readers: in a randomized crossover study (Chang et al., 2015), reading on a light-emitting e-reader for several hours before bed led to longer time to fall asleep, less melatonin, a later clock and lower alertness the next morning than reading a printed book.
• Screens with tuned light: a 2023 lab study of 72 healthy men (Schöllhorn et al.) kept screen brightness and color appearance the same but changed the melanopic content. Lower-melanopic light shortened the time to fall asleep and reduced melatonin suppression. The authors concluded: “We identify melanopic irradiance as an appropriate parameter to mitigate the unwanted effects of screen use at night.”

These were controlled lab studies, mostly in young adults, so they show the mechanism more clearly than they predict any one person’s sleep at home.

Expert targets for the evening

The 2022 consensus (Brown et al.) uses melanopic EDI, which measures how strongly light drives the clock’s light sensors:

Most people don’t own a melanopic light meter. A practical reading: a couple of low lamps rather than overhead lights, warm-colored bulbs, dimmed screens held further away, and a dark bedroom. Pair this with bright daytime light, as in the morning sunlight protocol, since bright days and dim evenings work together.

Lux on a meter is not melanopic lux

An ordinary lux meter measures how bright light looks to the eye’s cone cells. The consensus paper shows that common white sources all set to 300 lux can deliver very different melanopic EDI, because their spectra differ. It measures light at the eye, in the vertical plane at about 1.2 m height, roughly where a seated person’s eyes are. Two practical consequences:

• Warmer, lower-melanopic bulbs give less clock-driving light for the same visible brightness, which is why the authors suggest light sources with less short-wavelength content for evenings.
• Light that reaches your eyes counts, not light on the desk. A lamp beside you that lights the room indirectly matters less than a bright screen in front of your face.

Light while you sleep

The bedroom target of no more than 1 lux is the strictest of the three. In a 2022 lab study of 20 young adults (Mason et al.), one night of sleep under moderate room light of 100 lux raised night-time heart rate, lowered heart rate variability, and increased insulin resistance the next morning, compared with sleep in dim light below 3 lux. The room-light group also spent more time in lighter stage N2 sleep and less in slow-wave and REM sleep. This was one night in healthy volunteers, so it shows a short-term physiological effect rather than a long-term health outcome.

The consensus suggests blackout blinds and installing low orientation lighting where needed. If you need to see at night, it allows up to 10 lux melanopic EDI for the activity, which is still far below normal room light.

Comparing the common fixes

Blue-blocking glasses and night mode

• Amber or orange lenses: a 2020 meta-analysis of 12 studies (Shechter et al.) found the results inconsistent. The pooled effects on sleep efficiency and total sleep time were small to medium, and the benefits appeared mainly in people with insomnia, bipolar disorder, delayed sleep phase or ADHD.
• Blue-filtering lenses: a 2023 Cochrane review of 17 trials rated the evidence on sleep quality as very low certainty.
• Night mode: shifting the color lowers the melanopic content, which the 2023 screen study suggests matters. But a bright warm screen is still bright, so dimming and stopping earlier remain the bigger steps.

A simple evening routine

These steps follow from the studies above; none has been tested as a package.

• 3 hours before bed: switch from overhead lights to low lamps, in line with the expert targets.
• Screens: turn brightness down, use warm color settings, and put them away earlier when you can.
• Bathroom at night: use a dim night light rather than the main light.
• Bedroom: blackout curtains or an eye mask for the darkest sleep environment.

For the wider sleep picture, see the complete sleep guide.