Sleep regularity predicts mortality risk better than sleep duration in UK Biobank

Sleep researchers have long focused on how many hours we spend in bed, but a new UK Biobank analysis shows that the consistency of our sleep‑wake schedule may be a more powerful signal of longevity. By processing over 10 million hours of accelerometer data from 60,977 adults, the team calculated a Sleep Regularity Index (SRI) and tracked mortality outcomes for up to 7.8 years. Participants with the highest SRI quintiles experienced 23‑48 % lower all‑cause mortality risk and similar reductions in cancer and cardiometabolic deaths compared with the least regular sleepers. The association held after adjusting for age, sex, ethnicity, socioeconomic status, and lifestyle factors. These findings suggest that regular sleep timing could be a missing piece in public‑health guidelines that currently emphasize sleep duration.

What happened

The investigators used wrist‑worn accelerometers to derive an SRI for each participant, summarizing day‑to‑day variability in sleep onset and offset over a 7‑day monitoring period. The median SRI was 81.0 (IQR 73.8‑86.3) in a cohort with a mean age of 62.8 ± 7.8 years, 55 % female. Over a median follow‑up of 7.8 years, 1,859 deaths were recorded.

Higher SRI scores were linked to a 23‑48 % reduction in all‑cause mortality, a 17‑39 % reduction in cancer mortality, and a 27‑57 % reduction in cardiometabolic mortality when comparing the top four quintiles to the least regular quintile. These risk gradients persisted after sequential adjustment for demographic, socioeconomic, and lifestyle covariates. By contrast, sleep duration showed a weaker and non‑linear association with mortality, confirming that regularity outperforms duration as a predictor.

Why it matters

If sleep regularity is indeed a modifiable determinant of longevity, public‑health messages may need to shift from “how many hours” to “when you sleep.” Consistent timing could be a low‑cost lever for reducing premature death, especially for cardiometabolic and cancer outcomes that dominate mortality statistics. Employers, clinicians, and wearable‑tech developers can leverage this insight to design interventions, counseling, and algorithms that prioritize schedule stability alongside total sleep time.

How to think about it

Treat sleep regularity as a habit metric similar to daily exercise. Aim for a bedtime window that varies by no more than 30 minutes across weekdays and weekends, and keep wake‑up times equally stable. Use smartphone or wearable sleep trackers to monitor your SRI or simply log sleep times in a spreadsheet. When irregularity spikes—such as after travel or shift‑work—plan recovery periods with consistent sleep windows before returning to a normal schedule. Pair regularity with adequate duration (7‑9 hours for most adults) to maximize health benefits.

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