Definition
- Sleep debt
- Sleep debt is the cumulative difference between the sleep you need and the sleep you actually get. It builds across consecutive short nights and produces measurable declines in alertness and performance that people are typically poor at self-assessing.
Can you repay it?
Partially. A long weekend lie-in recovers some alertness, but studies consistently find that recovery sleep does not fully restore performance after a run of restricted nights, and the lie-in itself shifts your rhythm later — which makes Monday harder.
Shortening the debt is more effective than repaying it: adding thirty minutes a night across a week beats adding four hours on Saturday.