The evidence is convergent. Multiple independent sources reach the same conclusion, the underlying mechanism is well-characterized, and even the field's most cautious voices treat it as worth doing.
And in sleep, we are, our sleep is broken up into 90 minute segments. Early in the night we have more phase one and phase two lighter sleep. And then we go into our deeper phase three and phase four sleep. And then we return to phase one, two, three, four. So all night, you're going through these ultradian rhythms of stage one, two, three, four, one, two, three, four, it's repeating.
Every Sunday: the week’s new conflicts and verdict changes — and nothing else.
Native comments, Twitter mentions, and Reddit threads about this claim — surfaced together so the conversation isn't fragmented across platforms.
Bookmarking — the dossier-vs-overview split is the right call. Most of the time I want overview; sometimes I want receipts.
Would love a "what would change this verdict" RSS feed. Sign me up if it exists.
And sleep, regardless of how long we sleep is generally broken up into a series of 90 minute cycles. These ultradian cycles.
And in sleep, our sleep is broken up into 90-minute segments. Early in the night, we have more phase 1 and phase 2 lighter sleep. And then we go into our deeper phase 3 and phase 4 sleep. And then we return to phase 1, 2, 3, 4. So all night, you're going through these ultradian rhythms of stage 1, 2, 3, 4, 1, 2, 3, 4. It's repeating.
And sleep, regardless of how long we sleep, is generally broken up into a series of 90-minute cycles, these ultradian cycles.
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.