Light exposure
Blue-blocking glasses moved melatonin onset 28 minutes earlier in pregnancy
At a glance
| Study type | Randomized controlled trial |
|---|---|
| Year | 2022 |
| Journal | Neurobiology of Sleep and Circadian Rhythms |
| Effect size | 28 min earlier melatonin onset |
| Population | Pregnant |
| Dose / protocol | Amber-tinted glasses 2-3 hours before bed |
Background
A randomized controlled trial in nulliparous third-trimester women compared full blue-blocking amber glasses to partial blue-blockers. Full-block glasses worn 2–3 hours before bed shifted dim-light melatonin onset 28 minutes earlier.
Why does pre-bed light matter so much in late pregnancy?
Third-trimester sleep is fragmented by physical discomfort, frequent waking, and increased sympathetic tone. Anything that strengthens the circadian melatonin signal — including reducing evening blue-wavelength light exposure — buys back sleep that pregnancy is already taking.
What kind of glasses, and when?
Amber-tinted glasses that visibly block short-wavelength (blue) light, worn 2–3 hours before bedtime over normal indoor lighting. Partial blue-blockers (clear lenses with a coating) showed substantially smaller effects.
Are amber glasses safer or simpler than 'night mode' on a phone?
They cover all light sources in your environment, not just the phone screen. Phone night mode reduces a single source's blue content but does nothing about the room's ceiling LEDs or a TV across the room — which often dominate the retinal exposure.
Does this generalize outside pregnancy?
There is broader literature in non-pregnant adults supporting evening blue-light reduction. The reason this trial earns its own page is that it specifically recruited third-trimester women — most evening-light trials don't, so this is the cleanest perinatal evidence.
How does Solas use this?
If you log late sleep onset and your stage is third-trimester, Solas may recommend a 2–3 hour amber-glasses block before bed and prompts you to log onset latency the following morning to see whether your own data tracks the trial finding.
Source
Liset R, Gronli J, Henriksen RE, Henriksen TEG, Nilsen RM, Pallesen S
(2022).
A randomized controlled trial on the effect of blue-blocking glasses compared to partial blue-blockers on melatonin profile among nulliparous women in third trimester of the pregnancy Neurobiology of Sleep and Circadian Rhythms.
DOI: 10.1016/j.nbscr.2021.100074
Read the original paper →
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