Duration

• Caffeine

  Keep caffeine early, and keep late doses small.

• Screens

  Put screens away before getting into bed.

• Timing

  Move your bedtime earlier, not your wake time later.

What It Is

How much sleep you get on a typical night.

Why It Matters

Sleep duration and all-cause mortality follow a U-shaped relationship: the evidence suggests risk is lowest in the 7–9 hour range and rises at both ends. The short end is the weaker half, where the studies disagree and some of the largest analyses find no clear difference below 7 hours. Sleeping outside the range is linked to cardiovascular and metabolic disease as well, and the leading sleep authorities recommend at least 7 hours for adults.

The two ends of the curve are not the same problem. Short sleep has direct mechanisms: it disrupts glucose regulation, raises blood pressure, drives inflammation, and cuts short the overnight recovery that immune and brain function depend on. Long sleep, beyond about 9 hours, behaves more like a symptom than a cause, since illness, depression, and fragmented sleep all push time in bed up, so that association is partly reverse causation.

Treat 7 hours as a floor, not a target to beat by a little. Protect a window long enough to actually reach it, and if you regularly fall short, move your bedtime earlier before reaching for anything else. More is not better past your own need, and the aim is a steady night in range rather than an occasional long one.

• 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
• Watson, N.F. et al. (2015). Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. doi.org/10.5665/sleep.4716
• Saint-Maurice, P.F. et al. (2024). Associations between actigraphy-measured sleep duration, continuity, and timing with mortality in the UK Biobank. Sleep. doi.org/10.1093/sleep/zsad312
• 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
• Chen, Y. et al. (2026). Associations of sleep duration and insomnia with cardiometabolic disease onset, multimorbidity, and mortality: A prospective study in 461,046 Chinese adults. Sleep Medicine. doi.org/10.1016/j.sleep.2026.109073
• Lin, Y.C. et al. (2026). All-Cause and Cardiovascular Mortality in Relation to Sleep Duration: A Community-Based Cohort With Over 30 Years of Follow-Up. Journal of Sleep Research. doi.org/10.1111/jsr.70458