Screens at night and sleep: what the science says

You watch a series until midnight, then toss and turn in bed. Is the screen to blame? Partly — but not for the reason you think.

The mechanism: light sets the clock

In the retina, specialised cells measure the amount of ambient light and inform your internal clock. They're particularly sensitive to blue wavelengths. In the evening, as the light fades, the brain releases melatonin, the hormone that prepares you for sleep. Bright light after sunset delays that signal.

What matters most is the intensity and duration of the light you receive. A powerful white ceiling light in the living room has more effect than a phone at low brightness. So the screen isn't the only culprit — but it's often the last thing switched on, twenty centimetres from your eyes.

What the studies show

• Exposure to bright light in the evening delays melatonin and falling asleep: that's well established.
• The specific effect of a screen at normal brightness is real but modest — a delay of a few dozen minutes in the most cited studies, not hours.
• Amber-tinted lenses, which block a large share of blue, have been tested in several small studies: some report falling asleep faster and better perceived sleep, others find no difference. The evidence is encouraging but limited. We prefer to tell it like that.

A routine that works in real life

Throwing your phone away at 7 pm isn't an option for most of us. Here's what's realistic:

1. Dim the room an hour before bed. It's the most effective habit, and the most forgotten. A warm table lamp rather than the ceiling light.
2. Turn on night mode on your phone, tablet and computer, automatically at sunset.
3. Lower the screen brightness to the lowest comfortable level.
4. Wear tinted lenses if the screen stays on late. An amber or orange tint filters far more blue than night mode. That's the job of SAFRAN, BRAISE and DUNE — our “evening” models.
5. Keep a regular schedule. Your internal clock loves routine more than any accessory.

Night mode or tinted lenses: what really changes

Both “warm up” what you see, but not in the same place. Night mode only changes the screen: it shifts its colours towards orange and lowers its blue light a little, without touching the ceiling light, the bedside lamp or the TV next to it. A tinted lens acts on everything that enters the eye: the screen, the room, the hallway light. It's more complete, and it's also why you have to take it off to drive.

In practice: if you only look at a phone in an already dark bedroom, night mode does most of the job. If you work late under white light, or watch TV in a well-lit living room, a tinted lens brings something night mode can't.

Test it honestly: two weeks

You're the best judge — as long as you test properly.

1. One week without glasses, noting each morning when you went to bed and how long it felt to fall asleep.
2. One week with tinted lenses, worn from 8 or 9 pm, without changing anything else: same times, same coffee, same series.
3. Compare. If the difference isn't clear, light wasn't your main problem — and you have 30 days to send the pair back to us.

This protocol is anything but scientific, but it avoids the “I bought it, so it works” effect. Many factors weigh more heavily than light on sleep: when you had your last coffee, alcohol, late exercise, stress, the temperature of the bedroom. A pair of glasses cancels none of them.

Blue light glasses for sleep: how to use them

If you want to try glasses to sleep better, four pointers:

• Choose tinted lenses. Amber or orange: they're the ones that filter a large share of blue light. Clear lenses filter too little to affect sleep. At SAY: DUNE (round) and BRAISE (rectangular).
• Put them on early. In studies, amber lenses are often worn two to three hours before bedtime, not five minutes before lights out.
• Take them off to sleep. You don't sleep in them: in the dark, they do nothing. Wear them during your evening screen time, then put them on the bedside table.
• Keep the rest of the routine. Dim lighting, regular hours, no late coffee: the glasses add to these habits, they don't replace them.

Before you buy, also take two minutes to read the downsides of blue light glasses.

Two precautions

A tinted lens changes colours: don't use it to edit photos, and never to drive at night. And if your sleep problems persist, talk to a doctor: light is only one factor among others (stress, caffeine, schedules, sleep apnoea).

For daytime, stick with clear lenses: here's how to choose.

Read next: Kids and screens: do they need blue light glasses? · Series and streaming: watching without tiring your eyes