How does sleep affect your life expectancy?
At age 40, the difference between the best and worst answer here is about 2.8 years of life expectancy — 2.9 for men and 2.7 for women. That is the gap between “7–8 hours” and “9+ hours”, holding everything else constant.
Sleep is usually the cheapest year available to anyone reading this. It needs no gym membership, no money and no dietary discipline. It is also the factor people most consistently believe they have beaten, which is why it appears near the middle of most people's results rather than the bottom.
What each answer costs, at 40
| Answer | Hazard ratio | Years vs. best |
|---|---|---|
| 7–8 hours | 0.97 | best |
| 6–7 hours | 1.02 | −0.5 |
| 5–6 hours | 1.12 | −1.5 |
| Under 5 hours | 1.25 | −2.6 |
| 9+ hours(often a symptom, not a habit) | 1.28 | −2.8 |
Computed from the SSA 2023 period life table with this factor’s hazard ratio applied and every other factor held neutral. Source: Cappuccio et al., Sleep 2010 (meta-analysis, 1.38M people).
Does it matter less as you get older?
Yes, and by a lot. A hazard ratio applies to the years you have left, so the same answer costs less in absolute terms the later you are asked it. That is an argument for changing it early, not for concluding it no longer matters.
| If you are now | Men | Women |
|---|---|---|
| 30 years old | 3.2 yrs | 2.8 yrs |
| 40 years old | 2.9 yrs | 2.7 yrs |
| 50 years old | 2.7 yrs | 2.5 yrs |
| 60 years old | 2.3 yrs | 2.2 yrs |
| 70 years old | 1.8 yrs | 1.9 yrs |
What the evidence actually shows
Cappuccio and colleagues pooled 16 studies covering more than 1.3 million people. Short sleepers — under six hours — carried about 12% higher mortality. Long sleepers, over nine hours, carried about 30% higher. The floor of the curve sits at seven to eight hours, and both tails are worse than the middle.
What to do about it
Seven to eight hours is the floor of the risk curve, and both ends are dangerous. Fixing sleep is usually the cheapest year on this list.
Where this number is weak
The long-sleep finding is very likely not causal. Sleeping ten hours a night is more often a symptom of an undiagnosed illness than a cause of one, and no trial has ever shown that shortening a long sleeper's night helps them. The short-sleep side has a more plausible mechanism, through blood pressure and glucose regulation.
More generally: these are observational cohorts, which show association rather than proof of cause. The full methodology sets out every simplification the model makes.
What is it costing you?
The calculator weighs this against your other nine factors and ranks them.
Then make it count. The Extension Plan turns your result into a 12-week plan, starting with the habit worth the most years to you · $9. See what is in it →