Regular sleep timing may be just as important as sleep length for long-term health.
Getting enough sleep is a central part of sleep advice, but the day-to-day consistency of sleep and wake times may also matter for long-term health. To test that idea, a study examined whether sleep regularity is linked to the risk of premature death.
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The study analyzed data from more than 60,000 UK Biobank participants who were about 63 years old on average and wore an activity tracker for one week. Using those records, researchers calculated a sleep regularity score, estimating how often participants were asleep or awake at similar times from one day to the next, and compared it with average sleep length. They then linked those sleep measures to death records for up to nearly 8 years.
- Sleep regularity was a stronger predictor of death rates from any cause over the study period than average sleep length.
- Compared with the least-regular fifth, the four groups with more regular sleep patterns had about 20% to 30% lower rates of death from any cause during follow-up, after the researchers accounted for demographic, lifestyle, social, and health factors.
- The two most regular sleep groups also had about **23% to 24% lower rates of death from cancer and about 31% to 38% lower rates of death from cardiovascular, diabetes-related, and other metabolic causes.
- As a practical anchor, the researchers noted that the most regular sleepers usually fell asleep and woke within about one-hour windows, compared with about three-hour windows in the least-regular group.
Sleep timing may matter because it helps organize many of the body's daily rhythms, not just sleep itself. When bedtimes and wake times shift from day to day, the timing of light exposure, meals, physical activity, and rest often shifts with them. These cues help synchronize the body's 24-hour rhythms across many organs and tissues, including rhythms involved in blood pressure, blood sugar control, inflammation, hormone signaling, and cellular repair. Irregular timing could therefore create a kind of repeated internal mismatch, where different systems are receiving less consistent signals that help coordinate the body's daily functions.
The study was observational, so it cannot determine whether irregular sleep timing contributed to higher death rates or simply reflected underlying health problems that increased the likelihood of both irregular sleep and earlier death. Nevertheless, the findings suggest that steady sleep and wake windows deserve attention alongside getting enough sleep each night. In episode #107, Dr. Michael Grandner and I explore treatment options for insomnia and science-backed strategies for better sleep.