Sleep is the one recovery practice with mortality data behind it, and the shape of the data is a U: both short and long sleep track with higher death rates. Seven to nine hours sits at the bottom of that U for most adults. It is free, and it is the base everything else rests on.
A systematic review and meta-analysis of prospective cohorts (over 1.3 million participants) found short sleep, under about seven hours, carried a 12% higher all-cause mortality risk, with the pooled curve bottoming out at seven hours or a little more. Observational data cannot exclude every confounder, but the consistency, size and dose-response shape across dozens of cohorts is why this grades Strong while other recovery fashions do not.
Doing it: Anchor your wake time first, seven days a week; bedtimes settle around it. Keep the room dark and cool, front-load caffeine before noon, and give yourself a wind-down half hour. If you snore loudly or wake unrefreshed despite enough hours, ask your GP about sleep apnoea testing.
Who it suits: Everyone. Shift workers face real constraints here; consistency of opportunity still helps where perfect timing is impossible.
Sources
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