What is sleep debt, and can you repay it?
Sleep debt is simple arithmetic: what you needed, minus what you got, added up. The interesting part is how it behaves.
How sleep debt builds
Every night you fall short of your sleep need, the shortfall adds to a running total. Miss an hour four nights in a row and you are carrying roughly four hours of debt, and the effects on focus, mood and recovery compound.
The debt that matters is measured against your real need, not a flat eight hours. If your need is seven and a half hours, a seven and a half hour night adds nothing, even though it is under the popular number.
Can you repay it?
Partly. A longer night or two can pay back recent debt, and the body is good at recovering the most important sleep first. But you cannot bank sleep far ahead, and chronic, long-run debt is not cleared by a single weekend lie-in.
The reliable fix is not heroic catch-up sleep, it is closing the nightly gap: getting near your real need most nights so the debt stops growing.
How TIDES reads it
TIDES tracks sleep debt against your own sleep need, not a flat number, and carries it forward day to day so a run of short nights is visible instead of forgotten. It uses that debt to shape tonight's recommended window and tomorrow's plan, honestly, from the sleep it can actually measure.
Common questions
What is sleep debt?
Sleep debt is the running total of the sleep you needed but did not get. Each night you fall short of your real sleep need, the shortfall adds up.
Can you repay sleep debt?
Recent debt can be partly repaid with a longer night or two, and the body recovers the most important sleep first. But you cannot bank sleep far ahead, and long-run debt is not cleared by one weekend.
Is sleep debt measured against 8 hours?
It should be measured against your real sleep need, not a flat eight hours. A night at your personal need adds no debt even if it is under eight hours.