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Circadian-Timed Light

Timed light exposure—bright morning light and dim evening light—entrains the circadian clock, advancing sleep timing and improving alertness.

Light & Circadian Phase

  • Morning light (6-10 AM): phase advance of 36-45 minutes
  • Evening light (6-10 PM): phase delays
  • Peak sensitivity at 460-480 nm (blue light)

Melatonin & Sleep

  • Blue light suppresses melatonin 50-80%
  • Dim warm lighting 2-3 h before bed preserves melatonin
  • Sleep onset advances 19-30 min with morning light

Evening spectral tools (pooled lens trials)

Shechter et al. 2020 (Sleep Advances; PMID 37192881; shechter-2020-blue-light-filtering-sleep-meta) meta-analyzed short-wavelength–reducing / amber-tinted lenses worn before nocturnal sleep—use for pooled effect-size context next to single-trial evening-room interventions on Evening light hygiene (evening-light-hygiene).

Practical Protocol

  • 30 min bright light (10,000 lux) within 2 h of waking
  • Dim lights and use amber tones (2200K) 2-3 h before bed

Tertiary map

Wikipedia: Melatonin (wikipedia-melatonin-overview) and Wikipedia: Light therapy (wikipedia-light-therapy-overview) connect melatonin physiology/suppression with bright-light / phototherapy vocabulary—verify lux, timing, and effect sizes in the linked PubMed trials, not article prose alone.

Evidence