Wearable devices like the Oura ring may inaccurately report sleep metrics such as REM sleep when sleep architecture is disrupted by medications due to lack of EEG capabilities.

10 minutes of bright outdoor light within the first hour of waking anchors the circadian phase and improves sleep onset that night.

Morning sunlight exposure shifts the cortisol awakening response forward, improving daytime alertness.

Long-term morning sunlight reduces age-related macular degeneration risk.

Sleep regularity predicts all-cause mortality more strongly than sleep duration.

Tracking deep sleep on a wearable accurately reflects EEG-measured slow-wave sleep.

Caffeine has a half-life long enough that consumption after 2pm measurably degrades deep sleep in slow metabolizers.