Do blue light glasses help you sleep? 31 trials read

The short answer

Probably not, if you already sleep reasonably well. Possibly, if you have a sleep problem.

That is not a dodge. It is the pattern running through nearly every trial, and it is why one reader swears by their glasses while another has them in a drawer.

There is something more important. The two claims these glasses are most often sold on, more melatonin and a protected retina, were never measured in the randomised evidence Cochrane collected. Not refuted: never measured.

What does the research say?

That last point is worth pausing on. Glasses sold on the argument that they protect your melatonin and spare your retina have been tested for neither in the best available randomised evidence.

Nor is that gap new. Six years earlier a separate systematic review reached exactly the same observation: it found no studies investigating effects on macular structure or function ^[2].

When should you wear blue light glasses?

If you take one thing from this article, take this.

Two things about that last number, because it is easily misread, including by us in an earlier version of this article.

Shorter sleep is not worse sleep. Total sleep time says nothing about depth, about REM, or about how you feel the next morning. Someone who falls asleep faster and wakes less often may need less time in bed for the same rest. The difference was not significant either. It is not evidence of harm and we should not have written it up as though it were.

And it was a wrist monitor. Actigraphy infers sleep from movement. It cannot see which stage you are in, so on REM and deep sleep, precisely what quality is about, this study simply has no data.

What it does show: the things participants noticed improved significantly, and the one device watching could not measure that improvement and found nothing else either.

What was never measured?

If you want to know whether glasses improve your sleep quality, somebody has to measure your sleep stages. That means electrodes, not a wristband.

Across the whole PubMed index, searching for these glasses together with polysomnography or sleep architecture returns three hits. One is about sleep paralysis and mentions the glasses only in passing, one is a case report of a single patient. That leaves one real trial.

That is one trial, in boys, with a screen as the light source. You cannot build a general conclusion on it, and that is precisely the point: after twenty years of selling, this is all there is on sleep quality in the sense most people mean the word.

Who do blue light glasses actually help?

The picture turns as soon as there is a problem to solve.

A systematic review of evening wear reached the same division: there was substantial evidence that time to fall asleep shortened, but in patients with sleep disorders, jet lag or variable shift work schedules ^[3]. For healthy sleepers that review had nothing comparable to report.

In recreational athletes the effect was there but small, and only on the subjective measures ^[12]. In pregnant women without sleep complaints there was no significant difference at all ^[6].

Do blue light glasses help mood disorders?

Blue blocking glasses are also studied as a treatment for mood disorders, and those trials are instructive because they are strictly designed.

In major depressive disorder with sleep onset insomnia there was no significant change in depressive symptoms, in either group ^[7].

In bipolar disorder the rhythm did move: the circadian rhythm advanced in the glasses group while it delayed in the placebo group, and that difference was significant. But the measured sleep parameters and the mood symptoms did not differ between the groups ^[8].

What did the newest trial in children find?

All three of those sit in the full text. None of them reaches a product page.

Six minutes may be real. But six minutes at p = 0.040, out of a run of comparisons with no correction, in research paid for by a party that sells glasses, is exactly the kind of result we know often vanishes on repetition. And the mechanism the whole sale rests on, melatonin, did nothing here.

What we think

If you sleep well, the odds that glasses add anything measurable are low. You will probably feel better about your sleep, which is not nothing, but it is not what the glasses are sold for.

If you struggle to fall asleep, work shifts or fly across time zones, the case is different. There the evidence points more consistently one way, and the glasses are cheap, reversible and low risk. That is a reasonable bet.

And do not let the glasses stand in for the light switch. This is the mistake most people make. Of the light that gets between you and sleep in the evening, most of it is not your screen but the ordinary lighting in the room. Leave that on until you lie down and you will fall asleep more slowly than if you had turned it off, glasses or no glasses. Dim first, filter second. The glasses are what is left to do when the screen has to stay on, not what you do instead.

What you should not believe: that it is settled that they protect your retina or preserve your melatonin. On the macula there is literally nothing, across two systematic reviews six years apart. On melatonin there are two trials with opposite results. That is not a refutation, but it is not a foundation either, and it is sold as though it were one.

And watch the harms. For a quarter of wearers the glasses simply do not sit comfortably, and in the Cochrane figures one in six reported increased depressive symptoms. If you try them, pay attention to how you feel and not only to how you sleep.

What we are doing next

Three things this article does not answer.

First, and it is why most people buy these glasses in the first place: do they help with tired eyes? That is a different question from sleep, with its own literature and its own answer. We have written a separate article on the glasses and tired eyes.

Then one thing that still has to wait.

Do these glasses block what they promise? Sellers usually do publish a figure, but a percentage is not a spectrum, and it rarely says at which wavelengths it holds. We are going to measure transmission per wavelength ourselves, for yellow, orange and red lenses, and publish those measurements.

And one we have since written up: what blue light actually does to your rhythm, separate from the glasses. The mechanism is real and well studied, which is precisely why it is so striking that it does not show up in the measurements when a lens is involved.