Sleep regularity may matter more than 8 hours, a 60,977-person study finds

Claim

8 HOURS GOOD ENOUGH?

Catch

ONE WEEK ONLY

Verdict

A CLUE, NOT A CURE

UK Biobank researchers used one week of wrist-accelerometer data from 60,977 adults (mean age 62.8) to calculate a Sleep Regularity Index: how similar each day's sleep-wake pattern is to the next. Over about 6.3 years, 1,859 participants died.

Compared with the least regular fifth, the most regular fifth had a 30% lower risk of death in the fully adjusted model (HR 0.70, 95% CI 0.59-0.83), and the top four quintiles ranged from 20% to 30% lower. The study's abstract quotes a 20% to 48% range because it spans the minimally and fully adjusted models; the minimally adjusted top-quintile estimate was 48% (HR 0.52, 95% CI 0.45-0.60). Fully adjusted, cardiometabolic deaths were 38% lower in the top quintile (HR 0.62, 0.42-0.91) and cancer deaths 24% lower (HR 0.76, 0.61-0.94).

Regularity predicted mortality better than duration in model comparisons (AIC: p below .001 minimally adjusted, p=.005 fully adjusted), although adding sleep duration to the regularity model did not significantly improve fit (likelihood-ratio p=.14-.20).

What "regular" looked like: the top 20% usually fell asleep and woke within about 1-hour windows; the bottom 20% within about 3-hour windows.

The catch: this is observational, so it cannot prove that irregular sleep causes earlier death. Sleep was measured for only one week, participants were 43-79 years old and 97.2% white, and the authors note that irregular sleep may be a marker of ill health as well as a cause. The fully adjusted models include possible mediators such as smoking, so the authors say the true effect size likely lies between the minimally and fully adjusted models.

SOURCES

1. Windred DP, Burns AC, Lane JM, Saxena R, Rutter MK, Cain SW, Phillips AJK. Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. Sleep. 2024;47(1):zsad253. doi:10.1093/sleep/zsad253
2. Commentary: Consistency is key: sleep regularity predicts all-cause mortality. Sleep. 2024;47(1):zsad285. doi:10.1093/sleep/zsad285
3. UK Biobank: https://www.ukbiobank.ac.uk

For information only, not medical advice. If you have ongoing sleep problems, such as trouble falling or staying asleep, or loud snoring with daytime sleepiness, talk to a doctor.

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