Sleep Lab · Eye & light · 5 min read
Does blue light before bed actually matter?
The honest answer is less dramatic than the one you have heard. The strongest thing we can point to is not the colour of the light at all — it is what the screen keeps you doing after you meant to stop.
What does the evidence actually show?
Users were much more likely to remain on Reddit one to three hours after their respective estimated average bedtimes.Sleep Medicine (journal) · Meyerson et al. · via Medical Xpress · 2023-05 · study authors · source
The largest behavioural study we can point to did not measure light colour at all. Researchers at Duke and Yale reconstructed the bedtimes of tens of thousands of Reddit users from the timestamps of their posts, then looked at what happened on nights when someone posted close to that bedtime. On those nights they were still on the site one to three hours later. The more they posted, the later they stayed.
Read that carefully: the variable was not the colour of the pixels, it was the activity — and specifically the kind of activity that waits for an answer. A posted comment has a reply coming. An open feed has a next item. Both hand you a reason to carry on that has nothing to do with what the light is doing to your eyes.
The researchers were also clear about the limits. Bedtimes were estimated from posting patterns rather than reported by the users, and the study could not see people who read without posting. It is evidence about posting before bed, not a measurement of every kind of screen use.
What are we not going to tell you?
There is a widely repeated story about the colour of the light and a hormone, and you will find it on thousands of pages. We are not going to repeat it here. We have not verified it to the standard we would need before putting it on a page with our name on it, and a claim we cannot stand behind is worth less to you than no claim at all. Everything below rests on behaviour you can change tonight and check for yourself.
What should you change tonight?
- Put it down before you dim it. The order matters. Dimming a screen you are still using solves the smaller problem and leaves the larger one running. Set the phone down first, then deal with the light.
- Watch out for the open loop. Posting, replying and refreshing all wait for something to come back. A finished paper book does not. If you need something to do in the last hour, choose the kind that ends.
- Change the room, not just the device. Switch the overhead light off an hour before bed and leave one warm lamp low. The room should get darker before you are asked to fall asleep in it.
- Keep the phone out of arm reach. Face-down beside the bed it will be checked at 3am, and that check costs more than the minutes it takes.
None of this is medical advice. If you have not slept properly for months, or it comes with low mood you cannot shift, that is a doctor's question rather than a lighting one.
About AERÉ
AERÉ is a sleep and everyday-wellness home brand based in Hangzhou, China, designing twenty things for the hour before bed.
Questions people ask next
We would not start there. The behaviour in the hour before bed is the larger lever and it costs nothing to change. Sort the habit, then decide whether the glasses are worth it.
It deals with the light and does nothing about the loop. A warm filter on a feed you are still scrolling is the smaller half of the fix.
The study could not measure it — it only saw posts. What we can say is that anything which hands you a next item keeps the loop open, and a finished book does not.