Hormonal
Evening exposure to blue-enriched light (peak sensitivity ~460-477 nm) suppresses melatonin secretion and shifts circadian phase, with effects occurring rapidly and recovering quickly upon cessation.
If you are sensitive to sleep disruption, minimize exposure to bright, blue-rich light (LEDs, screens) in the 2 hours before bed. Even low levels (5-10 lux) can trigger circadian responses. If you must use light, choose warmer colors (longer wavelengths >600nm) and keep intensity low. Note that effects reverse quickly once the light is off.
a two-hour exposure to blue light (460 nm) in the evening suppresses melatonin, the maximum melatonin-suppressing effect being achieved at the shortest wavelengths (424 nm, violet)... Melatonin concentration recovered rather rapidly, within 15 min from cessation of the exposure... The review enables further development of an evaluation method of light pollution in LCA regarding the light-induced impacts on human circadian system.
Why this rating
Based on a systematic review of 128 articles, with 15 high-quality studies meeting strict criteria (sample size >20, spectral details provided).
Source
Systematic review of light exposure impact on human circadian rhythm
Leena Tähkämö et al. · Chronobiology International · 2018
DOI 10.1080/07420528.2018.1527773
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