The result of recurrent sleep deprivation that occurs over time, when an individual does not obtain a sufficient amount of restorative daily sleep. Sleep debt is like a monetary debt; it must be paid back at some time. The larger the sleep debt, the stronger the tendency to fall asleep. This accumulation of "lost sleep" may contribute to a decreased quality of life, the onset of related health problems, and the increased risk of injury and/or accident. See Sleep Deprivation.
Sleep debt is the cumulative effect of not getting enough sleep. A large sleep debt, for example, would suggest that a person is mentally or physically fatigued due to insufficient sleep. There is debate in the scientific community over the specifics of sleep debt.