2020 December 3 Note: It seems that this effect might be due to blue and green light. I will update this page accordingly eventually. Also this article is old and not my best work.
I wear blue-light blocking glasses every night. Here's why—
Attenuation of short wavelengths alters sleep and the ipRGC pupil response
21 subjects (aged 17-42) were asked to wear glasses that block 99% of blue light. The glasses were worn for at least 3 hours before sleep for two weeks. Melatonin (a sleep hormone that peaks during sleep) was measured (via saliva) before and after the experiment.
At the beginning of the experiment, melatonin was measured to be 16.1 pg/mL on average between the subjects. Melatonin was measured at night.
After two weeks, the average was 25.5 pg/mL, a 58% increase. (P = 0.0005)
Additionally, sleep duration increased by 24 minutes. (P = 0.001)
Subjects were instructed to sample their own saliva just before their normal bedtime. This is discussed further under "Melatonin analysis" in the paper.
Do saliva measurements of melatonin reliably predict melatonin levels within the body?
I wear these glasses every night. They are made by the same brand as the glasses that were used by the study. (The brand was not affiliated with the study.)
If you would like to get a pair for yourself, this is what I use. (This is an Amazon affiliate link; I’m required to say verbatim “As an Amazon Associate I earn from qualifying purchases.”)
I've been wearing these exact glasses since 2017, and in my experience they last at least a year. (Also, these glasses do have adjustable angle and length. The lens also pops out for easy cleaning. This took me a year to figure out.)
Note that other "blue light-blocking" glasses say they block blue light, but fail to say how much. I do not know of any effective glasses (blocks 80%+) that are not bright orange.
One more note: while some other blue-blocking glasses may have good lenses that block a meaningful amount of blue light, I'm not sure how much that matters if the glasses don't wrap around your eyes. Especially if the glasses still allow you to see blue from the brightest part of a room (the ceiling).
This is not an exhaustive review. I have only briefly reviewed other papers investigating this question. I have heard of in vitro evidence against "less blue light → better sleep", but I am yet to see any in vivo counter-evidence.
This is another study to consider. It draws the same conclusion as the study above. There's a nice graph on page 5 comparing teenage males that wore the glasses with those that didn't. I haven't had the time to review this other paper deeply, though.
Having trouble accessing the paper? Use SciHub.
[More papers via Google Scholar search]
This is also why I set my light bulbs to go red (and dim) after ~6:30pm.
Random tips on sleep.
Posted 2020 July, last updated 2020 September.
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