What is sleep debt and can you really catch up?

Sleep debt is the cumulative deficit that builds up when you consistently get less sleep than your body needs. If you need eight hours but only get six, you accumulate two hours of debt per night, and this compounds over time, impairing cognition, mood, metabolism, and immune function. The research on catching up is mixed. Short-term debt from a few bad nights can largely be recovered with extra sleep over a weekend, restoring alertness and some cognitive function. However, chronic sleep deprivation is harder to fully reverse. Studies suggest that while you can reduce the feeling of sleepiness, some cognitive deficits and metabolic damage from long-term sleep loss may not completely resolve even after recovery sleep. Consistent nightly sleep remains far more effective than trying to compensate later.