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Episode 79 · Sleep, Recovery & the Body
Why Bright Nights Delay Sleep
If you feel tired but not sleepy, your light timing may be sending mixed signals. Melatonin is one of the brain's night-timing signals.
The Science
- Hattar et al. (2002), Science: light-sensitive retinal ganglion cells (melanopsin) signal the brain's clock about time of day.
- That timing signal influences when melatonin, a darkness message, can rise.
- Bright light late at night makes night feel less clear to the system, while morning light anchors day has started.
- Feeling tired but not sleepy can be a light-timing mismatch.
The Protocol
- Bright days and dimmer nights: get outdoor light early when you can.
- In the last hour before bed, lower overhead brightness.
- Move screens farther away or make them less intense.
- Notice the signal, name the mechanism, and change one input before autopilot.
One-page summary
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The science beat (5-sec loop)
Sources
- Hattar S, et al. Melanopsin-containing retinal ganglion cells: architecture, projections, and intrinsic photosensitivity. Science. 2002;295(5557):1065-1070.
Educational content only. Not medical advice.
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