Sleep & life expectancy
Seven to eight hours is the longevity sweet spot; both too little and too much are linked to higher mortality.
Why it matters (the mechanism)
Sleep is when the body repairs cells and regulates hormones and blood pressure. Short sleep raises cardiometabolic risk; very long sleep often flags underlying illness.
The evidence
Mortality is lowest at about 7–8 hours; under 6 and over 9 hours both increase risk in large cohort studies.
What to do
- Protect a consistent 7–8 hour window, including on weekends.
- Keep a cool, dark room and a steady wake time to anchor your body clock.
- If you sleep enough but wake unrefreshed, get checked for sleep apnoea.
- Limit late caffeine, alcohol and screens, which fragment deep sleep.
And the chance of reaching 100?
Your odds of reaching 100 rise steeply with your overall forecast. As an illustration, a forecast age of 85 implies roughly a 6.7% chance of reaching 100; a forecast of 92 implies around 21%. Factors like sleep shift where your forecast lands. Get your personal figure in the calculator.
These figures are population-average estimates from peer-reviewed research, applied on top of the official life-table baseline for your country, sex and birth cohort — the US Social Security Administration period life tables, the UK Office for National Statistics, and the WHO Global Health Observatory. They describe statistical tendencies, not personal certainties, and are not medical advice.
Other factors
Frequently Asked Questions
See how sleep and everything else combine in your forecast — plus your chance of reaching 100.
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