Study

Sleep duration and all-cause mortality: a systematic review and meta-analysis

Cappuccio FP et al. · 2010 · Sleep

What it found

Meta-analysis of 16 prospective studies (>1.3M participants): both short (<7h) and long (>9h) sleep durations were associated with significantly increased mortality risk.

How we grade it

Every study behind a HALE recommendation is graded A to D on design, size and how consistently the finding replicates. Tap the bars above for the full breakdown of what grade A means and how much weight to give it.

Read the original paper

Where this shows up in HALE

Both too little and too much sleep raise mortality

The U-shaped curve you've probably heard about — with the actual numbers.