Sleep regularity
Hit the same bedtime within a 30-minute envelope. Stronger mortality signal than total hours slept.
Why
Cohort studies of older adults consistently show that going to bed and waking at consistent times, within a roughly 30-minute window, predicts mortality risk independent of how many hours someone sleeps. The body's circadian system entrains to expected timing; irregularity creates a low-grade jet-lag effect day after day.
Slot in your day
How to do it
How
Pick a target bedtime. Hold it within ±30 minutes, including weekends, for 4 weeks. Pair with morning sunlight within an hour of waking.
Ideal for
Anyone with shifting work hours or weekend social rhythms.
Sticking with it
Pick the bedtime that's actually possible 6 nights a week, not the aspirational one.
Markers this may influence
Evidence
Windred 2024 Sleep (UK Biobank, n=60,977, mean 6.3-y follow-up): higher Sleep Regularity Index was associated with 20–48% lower all-cause mortality across the top four quintiles vs. the most irregular. Notably, sleep regularity outperformed total sleep duration as a mortality predictor.