Best Sleep Mask? Why I'd Make Your Bedroom Dark Instead

You woke up at 6:40 already tired. You slept. Technically. Your phone says seven and a half hours, and the ring on your finger agrees. So why does it feel like you spent the night half listening for something? Like your body never quite got the message that it was allowed to switch off?

The best sleep mask, in my view, is the one you don't need: a bedroom that is fully dark, cool and free of unnecessary electronics. Sleep masks do cut the light reaching your eyes, and one study found they improved next-day memory and alertness, but most are made from synthetic foam and polyester that sit warm against your skin all night, and Bluetooth models put a radio transmitter against your head for eight hours. Research shows that even 1 to 10 lux of light during sleep can fragment sleep, so the goal is to remove light from the room, not just from your eyes.

Think about two kinds of mornings. In one, you wake a few minutes before the alarm, your head is clear and your body feels like it has actually been somewhere restful. In the other, you've been horizontal for eight hours and feel like you rested for three. Ask yourself now: which of those two is you, most weeks?

The sleep mask study everyone quotes

If you already sleep in a mask, I want to say something before I go any further. First of, I think it is great that you took steps to improve your sleep! You bought it because your room isn't dark enough, and that is exactly the right instinct. Most people never even notice the light. You did.

The mask does something, no doubt, I have one for long flights. A 2022 study from Cardiff University, published in the journal Sleep, had 94 young adults sleep one week with an eye mask and one week without. With the mask, they encoded new memories better and had faster reaction times the next day, and a second experiment linked the memory benefit to more time in slow-wave sleep. You can read the full paper here: Greco et al., Sleep 2022.

Mask sellers love this study. I love it too, but for a different reason. Look at what it actually proves: ordinary bedroom light, the kind those students were sleeping in every night, was costing them measurable brain performance. I will say that again, they made a change by covering their eyes, their sleep improved, this shows something was wrong in the environment - it was too light! Blocking some of it helped. That's not an argument for masks. It's an argument for darkness, and a mask is the smallest, leakiest, least complete version of darkness you can buy. Once again, we did what humans do, we provided a solution for the symptom, but didn't correct the underlying problem

Because here's what a mask does over a real night. It slides (how many times have you found it up on your forehead at 4am?). It presses on your eyes and traps heat against your face. And it leaves every other light in the room exactly where it was, falling on the rest of you.

How little light it takes to disturb your sleep

You've probably noticed that you sleep differently at the hytte. Deeper, somehow. People put it down to the mountain air or the quiet, and those help. But often it's the only place you sleep where it gets properly, completely dark, the only light is the moonlight?

The reason is a small group of cells in your retina that most people have never heard of. Alongside the rods and cones you see with, you have intrinsically photosensitive retinal ganglion cells, which contain a pigment called melanopsin. They don't build images. Their job is to tell your brain's master clock whether it's day or night, and they report straight to the system that controls melatonin. They are far more sensitive than you'd expect.

A 2019 study in PNAS from Monash University tested 55 young adults under evening light from 10 to 2,000 lux. On average, melatonin was cut by half at under 30 lux, which is dimmer than a typical living room at night. The part that stopped me was the range between people: the most sensitive person hit that halfway point at around 6 lux, the least sensitive at 350. That's more than a fifty-fold difference in how the same room affects two different bodies (Phillips et al., PNAS 2019). You might be the 350 lux person. You might be the 6 lux person. Nobody has told you which.

That was evening light, while awake. What about light while you're actually asleep, eyes closed? A Korean sleep lab study put healthy adults to bed one night in darkness and the next night under just 5 or 10 lux. With the light on, they spent more time awake after falling asleep, more time in the shallowest stage of sleep and less in stable stage 2 sleep (Cho et al., Chronobiology International 2016). A Slovak study went lower still, testing people in their own homes. At 1 lux all night, melatonin held up but sleep got more fragmented. At 5 lux, melatonin dropped too, and that was from a dim, warm-looking LED, the kind of light most people would assume is harmless ((Stebelova et al., 2020).

And it isn't only about sleep. A 2022 study published in PNAS found that healthy adults who slept a single night under 100 lux overhead light had a higher heart rate through the night, lower heart rate variability and increased insulin resistance the next morning, compared with a night under 3 lux (Mason et al., PNAS 2022). One night. Your body keeps running its night shift of metabolism and repair whether the lights are on or not. It just does a worse job of it.

Now walk through your own bedroom in your head. The router in the hallway throwing a green glow under the door. The clock with numbers. The smoke alarm blinking every minute. The street lamp outside that, in January, bounces off fresh snow and turns the whole window pale orange. And the spotlights in the ceiling, the ones every new and modernised Norwegian apartment seems to have now (perhaps you're lying under some right now). Bright, clean, modern. It looks great. Wonderful, but it isn't wonderful for your body when the dimmer sits on "nearly off" while you drift to sleep.

Why your eyelids aren't the whole story

I want to separate what we know from what we're still finding out here, because I think that matters in this field more than most.

What we know: your eyes are the main route by which light reaches the circadian clock, and closed eyelids don't block it completely. Eyelids let a small fraction of light through.

What we're still finding out: whether the rest of your body registers light at night in ways that matter. Researchers have found light-sensitive opsin proteins in human skin and other tissues, and Dr. Jack Kruse and others argue that the body reads its light environment through far more than the eyes. The human evidence here is early. I wrote more about this in Your Skin Is Watching, and in a more practical way in my post on whether red light works through the eyes or the skin.

There's also a deeper reason I care about darkness, and it goes beyond feeling sleepy. Dr. Russel Reiter has spent decades showing that melatonin isn't only a sleep signal. It works as an antioxidant targeted at your mitochondria, the part of each cell that makes energy and produces most of its free radicals (Reiter et al., 2017). So when a few lux of "warm white" light quietly lowers your night-time melatonin, it isn't just a sleep problem. It's your cellular repair crew turning up to work with half the tools. Given that, I'd rather make the whole room dark than bet on my eyelids and a strip of foam being the only things that count.

What most sleep masks are actually made of

Next time you take your mask off in the morning, notice the skin underneath. Warm. Often slightly damp. Then turn the mask over and read the care label (yes, I've done this in shops). Most of the masks topping the "best sleep mask" lists are polyester, memory foam, which is polyurethane foam, or "silky" satin, which is almost always polyester too. The contoured 3D ones are usually moulded foam from edge to edge.

I haven't found anyone who has measured what a sleep mask off-gasses. So we have to borrow from neighbouring research, and I'll be clear that it is borrowing. A 2014 study in Environmental Science and Technology measured volatile organic compounds (VOCs) coming off the foam in 20 crib mattresses. At body temperature the foam released about two and a half times more VOCs than at room temperature, polyurethane released a wider range of compounds than polyester, and the air where the baby breathed carried more than the rest of the room (Boor et al., 2014). A mask is not a mattress, and the amounts will be far smaller. But it is warm synthetic foam a few centimetres from your nose for a third of your life. I don't see what you gain.

Then there's heat. Your body has to drop its core temperature to fall into deep sleep, and it dumps a lot of that heat through the skin, including the face. A review of the research on sleep and temperature found that when people sleep with normal bedding, heat exposure increases time awake and reduces both slow-wave and REM sleep (Okamoto-Mizuno and Mizuno, 2012). A mask alone won't overheat you. But it's one more small piece of insulation in the wrong place, and small things add up at 3am.

Bluetooth sleep masks and the EMF question

A growing number of sleep masks have headphones built in. White noise, a podcast, a guided wind-down, straight into your ears. I understand the appeal, especially if you share a bed with a snorer. But think about what's physically happening. You're strapping a Bluetooth radio a few centimetres from your brain and leaving it on for the eight hours your body is meant to spend repairing itself.

Dr. Jack Kruse has argued for years that night is when your biology most needs a break from man-made electromagnetic fields (nnEMF), because that's when melatonin and your mitochondria do their repair work. That's his interpretation and quite frankly it is very compelling in my opinion. Others, who follow more centralised approach disagree. The research on radiofrequency fields and the brain is messy. A review by Heidi Danker-Hopfe's group in Berlin concluded that studies on waking brain activity are too inconsistent in their methods to allow firm conclusions (Danker-Hopfe et al., 2019). I am of the opinion, why risk it? The involvement of nnEMF on bioelectric beings (which you are) is very easily overlooked, but it shouldn't be.

Sleep studies keep turning up the same signal. In a double-blind, randomised crossover study at the University of Zürich, 25 young men were exposed for 30 minutes before bed to pulse-modulated radiofrequency fields, a pulsed magnetic field, or a sham. The radiofrequency exposure increased brain activity in the sleep spindle frequency range during the night that followed. Sleep stages didn't change and there was no clear effect on thinking the next day (Schmid et al., 2012). People will say Bluetooth transmits at much lower power than a phone held to your ear, but I say again, why risk it?

So I'm not going to tell you a Bluetooth mask is damaging you. I don't know that, and nobody else does either, I have my opinion and I think it is clear. What I can tell you is that the brain responds to these signals during sleep in controlled studies, and I can't think of a single benefit that justifies strapping a transmitter to my head every night when a dark, quiet room does the job without one. If you need sound, a small speaker across the room on a cable does the same thing.

While you're at it, give the whole bedroom a night off. Phone on flight mode or, better, in another room. A timer on the Wi-Fi router. And if you want to go a step further, this is where a grounding sheet comes in. The research on grounding (jording) is still small. The best-known study was a 2004 pilot where 12 people slept on a grounded mattress pad for eight weeks, and their night-time cortisol came down and their sleep improved, but there was no control group (Ghaly and Teplitz, 2004). I've written about grounding sheets and blue light blockers for the Norwegian autumn if you want the longer version, and you'll find the sheets in the grounding and PEMF collection.

The five-minute bedroom audit

Here's the test I give everyone who asks. Turn every light off, get into bed, wait a couple of minutes for your eyes to adjust, and hold your hand in front of your face. If you can see it, the room isn't dark enough.

I did this in my own bedroom a couple of years ago, fairly smug about it. I sell circadian lighting. Surely my room would pass. It didn't. The gap under my door let a strip of street light in my bedroom. One strip was enough to light up the bedroom quite considerable. I also noticed a small strip along one curtain edge. 2 light sources in the bedroom of a man who talks about light for a living. That evening was spent with tape and a small slice of humble pie. It might not the best, but it does the trick.

After that, it's mostly practical. Blackout curtains that reach right to the edges, with a pelmet or rail at the top so light can't spill over. Tape over the small LEDs you can't remove. Chargers, clocks and TVs out of the room altogether. In summer, especially the further north you are, the light nights make blackout blinds close to essential, and this is the one situation where I'd accept a mask as a stopgap, provided it's untreated silk or cotton with no foam.

Then turn the heat down. So many Norwegian bedrooms sit at 21 or 22 degrees all winter because the panel heater is on the same setting as the living room. For most people, somewhere between 16 and 19 degrees with a heavy dyne works far better, with the window open a crack if you can. Cool room, warm bed. Not cold, though: the same temperature review found that real cold changes heart activity during sleep even when sleep stages hold up, so this isn't a challenge to see how low you can go.

Good sleep starts at sunrise

Everything above is about the night. But bad sleep usually starts about twelve hours before you go to bed.

I go out on my terrace every morning, whatever the weather, including those November mornings when the rain is coming in sideways and it's barely light at eight. That's not toughness (well, a bit). The mornings I skip the terrace tend to be followed by those nights. Daylight through your eyes in the morning is what tells your clock when the day started, and therefore when the night should.

You might have noticed you get sleepy earlier after a few days på høstferie telt tur eller "sydentur". That's not your imagination. When researchers at the University of Colorado took people camping for a week with only natural light, their internal clocks shifted so that biological night began around sunset (Wright et al., Current Biology 2013). A follow-up found that even a single weekend of camping moved the evening melatonin rise almost an hour and a half earlier (Stothard et al., Current Biology 2017). Your clock isn't broken. It's just getting the wrong signals and something as simple as a weekend away in the mountains can help reset it.

In the evening, simply reverse it. When the sun goes down, the light in your home should get warmer and dimmer. I've written a guide to what bulbs to buy for healthy evening lighting, and you'll find the lamps in the circadian lighting collection. Screens are the other big one, and a pair of blue light blocking glasses for the last two or three hours before bed does a lot of the heavy lifting. (I caught myself on my phone at 11pm last Tuesday without my glasses on. Literally sell the things. Still get pulled in.) If you want to go further with all of this, start with how to reset your circadian rhythm.

So no, I don't sell sleep masks, and I'm not planning to start. If you'd like help working out where the light is getting into your bedroom, or what fits your evening routine, message me. That's what I'm here for.

This article is general information and isn't a substitute for medical advice. If you have long-term sleep problems, loud snoring or pauses in breathing at night, please talk to your doctor.

Frequently asked questions about sleep masks and dark bedrooms

Is it bad to sleep with a sleep mask every night?

For most people a sleep mask isn't dangerous, and in a bright room it's better than nothing. The problem is that most masks are made from synthetic foam and polyester that sit warm against the thin skin around your eyes for eight hours. A mask also does nothing about the light falling on the rest of your body or the rest of the room. A properly dark bedroom is a better and more lasting fix.

How dark does my bedroom need to be for good sleep?

Dark enough that you can't see your hand in front of your face once your eyes have adjusted. Sleep lab studies have found that 5 to 10 lux during sleep increased time awake and shallow sleep, and a 2020 study found that even 1 lux all night made sleep more fragmented. Blackout curtains, tape over small LEDs and moving electronics out of the room gets most people there.

Are Bluetooth sleep headphones safe to wear all night?

They transmit at much lower power than a mobile phone, but they put a radio transmitter against your head for the whole night. Controlled studies have shown that pulsed radiofrequency exposure before sleep can change brain activity during the night that follows, even though sleep stages didn't change. Nobody knows for sure what that means over years. I'd keep the bedroom as free of wireless signals as you can and use a wired speaker across the room if you need sound.

What should I do if I can't get my bedroom fully dark in summer?

Start with blackout curtains or blinds that cover right to the edges, with a rail or pelmet at the top so light can't leak over. In northern Norway in June you may not be able to shut the light out completely. In that case a mask made of untreated silk or cotton, with no foam, fragrance or electronics, is a reasonable temporary compromise. Treat it as a plaster rather than the solution.

Er det bedre å sove med søvnmaske enn å gjøre soverommet mørkt?

Nei, et mørkt soverom er bedre. En søvnmaske dekker bare øynene, mens et mørkt rom fjerner lyset helt, uten syntetisk skum mot huden. Studier viser at så lite som 1 lux hele natten kan gi mer oppstykket søvn. Blendingsgardiner, teip over små LED-lamper og elektronikk ut av rommet gir deg mer enn noen maske.

References

Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proc Natl Acad Sci USA. 2022;119(12):e2113290119. PubMed

Phillips AJK, Vidafar P, Burns AC, et al. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proc Natl Acad Sci USA. 2019;116(24):12019-12024. PMC

Cho CH, Lee HJ, Yoon HK, et al. Exposure to dim artificial light at night increases REM sleep and awakenings in humans. Chronobiol Int. 2016;33(1):117-123. DOI

Stebelova K, Roska J, Zeman M. Impact of Dim Light at Night on Urinary 6-Sulphatoxymelatonin Concentrations and Sleep in Healthy Humans. Int J Mol Sci. 2020;21(20):7736. PubMed

Greco V, Bergamo D, Cuoccio P, et al. Wearing an eye mask during overnight sleep improves episodic learning and alertness. Sleep. 2023;46(3):zsac305. PMC

Reiter RJ, Rosales-Corral S, Tan DX, et al. Melatonin as a mitochondria-targeted antioxidant: one of evolution's best ideas. Cell Mol Life Sci. 2017;74(21):3863-3881. PMC

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Okamoto-Mizuno K, Mizuno K. Effects of thermal environment on sleep and circadian rhythm. J Physiol Anthropol. 2012;31(1):14. PMC

Danker-Hopfe H, Eggert T, Dorn H, Sauter C. Effects of RF-EMF on the Human Resting-State EEG: the Inconsistencies in the Consistency. Part 1. Bioelectromagnetics. 2019;40(5):291-318. PMC

Schmid MR, Murbach M, Lustenberger C, et al. Sleep EEG alterations: effects of pulsed magnetic fields versus pulse-modulated radio frequency electromagnetic fields. J Sleep Res. 2012;21(6):620-629. PubMed

Ghaly M, Teplitz D. The biologic effects of grounding the human body during sleep as measured by cortisol levels and subjective reporting of sleep, pain, and stress. J Altern Complement Med. 2004;10(5):767-776. PubMed

Wright KP Jr, McHill AW, Birks BR, et al. Entrainment of the human circadian clock to the natural light-dark cycle. Curr Biol. 2013;23(16):1554-1558. DOI

Stothard ER, McHill AW, Depner CM, et al. Circadian entrainment to the natural light-dark cycle across seasons and the weekend. Curr Biol. 2017;27(4):508-513. DOI

About the author: Dominic Lamb runs LightTherapy.no from Drammen, Norway's oldest independent red light therapy and home light therapy store, founded in 2018. He tests every device with a spectrometer before stocking it, and appeared on the Din Helse podcast in February 2025. Read more about Dominic and why the store exists.