Sleep

• Regularity

  The day-to-day consistency of when you fall asleep and wake up.

• Duration

  How much sleep you get on a typical night.

• Efficiency

  How much of your time in bed you actually spend asleep.

What It Is

How long, how regularly, and how well you sleep.

Why It Matters

Sleep is a foundational longevity lever. Prospective cohort studies and meta-analyses consistently link healthy sleep to lower all-cause and cardiovascular mortality, with parallel signals for cancer mortality, and the effect holds across several distinct dimensions rather than any single number.

Those dimensions matter somewhat independently, though how far that holds varies between them. Duration follows a U-shaped curve with the lowest risk in the 7–9 hour range, and its long side is the one reverse causation threatens, since illness drives people to spend longer in bed. Regularity, the day-to-day consistency of your sleep and wake times, predicts mortality at least as strongly as duration, and does so independently of how long or how well you sleep; continuity, how much of your time in bed is actually spent asleep, is the one the studies disagree about. The likely mechanism is circadian and recovery biology: misaligned or fragmented sleep disrupts glucose regulation, blood pressure, inflammation, and overnight repair. A similar U-shape appears in biological measures of aging across several organ systems.

Because those dimensions carry separate signals, the behaviors in this area measure them separately, each with its own evidence-based target. The guidance beneath them covers the practices that move those numbers in the right direction.

• Cappuccio, F.P. et al. (2010). Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. doi.org/10.1093/sleep/33.5.585
• Sletten, T.L. et al. (2023). The importance of sleep regularity: a consensus statement of the National Sleep Foundation sleep timing and variability panel. Sleep Health. doi.org/10.1016/j.sleh.2023.07.016
• Liang, Y.Y. et al. (2023). Joint Associations of Device-Measured Sleep Duration and Efficiency With All-Cause and Cause-Specific Mortality: A Prospective Cohort Study of 90 398 UK Biobank Participants. The Journals of Gerontology: Series A. doi.org/10.1093/gerona/glad108
• Windred, D.P. et al. (2024). Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. Sleep. doi.org/10.1093/sleep/zsad253
• Li, H. et al. (2024). Association of healthy sleep patterns with risk of mortality and life expectancy at age of 30 years: a population-based cohort study. QJM. doi.org/10.1093/qjmed/hcad237
• Ungvari, Z. et al. (2025). Imbalanced sleep increases mortality risk by 14–34%: a meta-analysis. GeroScience. doi.org/10.1007/s11357-025-01592-y
• Chaput, J.P. et al. (2026). Dose-response associations between sleep duration and health outcomes in adults: comparison between self-reported and device-based measures. Sleep. doi.org/10.1093/sleep/zsag193
• O'Toole, C.K. et al. (2026). Sleep chart of biological ageing clocks in middle and late life. Nature. doi.org/10.1038/s41586-026-10524-5
• Zhang, Q. et al. (2026). Multidimensional sleep health and all-cause mortality: Counterfactual risk estimation and component-specific contributions in the sleep heart health study. Sleep Medicine. doi.org/10.1016/j.sleep.2026.109236