Sleep deprivation
Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary widely in severity. This means it can happen over both short and long periods of time. Sleep is important because adequate sleep, or restful sleep, is essential for maintaining overall health, brain performance, emotional regulation, and metabolic balance. Persistent sleep insufficiency can contribute to cognitive decline, emotional instability, and biological wear that has effects similar to accelerated aging. Scientific research demonstrates overwhelming evidence that inadequate sleep produces chronic consequences for overall health, ranging from attentional lapses to long-term neurodegenerative changes.
The human body and most living organisms depend on sleep for neural recovery. All known animals sleep or exhibit some form of sleep behavior, and the importance of sleep is self-evident for humans, as nearly a third of a person's life is spent sleeping. Sleep deprivation is common as it affects about one-third of the population.
The US National Sleep Foundation recommends that adults aim for 7 hours of sleep per night. Children and teenagers require even more sleep, ranging from 8–16 hours per night. For healthy young individuals with normal sleep, the appropriate sleep duration for school-aged children is between 9 and 11 hours. Acute sleep deprivation occurs when a person sleeps less than usual or does not sleep at all for a short period, typically lasting one to two days. However, if the sleepless pattern persists without external factors, it may lead to chronic sleep issues. Chronic sleep deprivation occurs when a person routinely sleeps less than the amount required for proper functioning. The amount of sleep needed can depend on sleep quality, age, pregnancy, and level of sleep deprivation. Sleep deprivation is linked to various adverse health outcomes, including cognitive impairments, mood disturbances, and increased risk for chronic conditions. A meta-analysis published in Sleep Medicine Reviews indicates that individuals who experience chronic sleep deprivation are at a higher risk for developing conditions such as obesity, diabetes, and cardiovascular diseases.
Insufficient sleep has been linked to weight gain, high blood pressure, diabetes, depression, heart disease, and strokes. Sleep deprivation can also lead to high anxiety, irritability, erratic behavior, poor cognitive functioning and performance, and psychotic episodes. A chronic sleep-restricted state adversely affects the brain and cognitive function. However, in a subset of cases, sleep deprivation can paradoxically lead to increased energy and alertness; although its long-term consequences have never been evaluated, sleep deprivation has even been used as a [|treatment for depression].
To date, most sleep deprivation studies have focused on acute sleep deprivation, suggesting that acute sleep deprivation can cause significant damage to cognitive, emotional, and physical functions and brain mechanisms. Few studies have compared the effects of acute total sleep deprivation and chronic partial sleep restriction. A complete absence of sleep over a long period is not frequent in humans ; it appears that brief microsleeps cannot be avoided. Long-term total sleep deprivation has caused death in lab animals.
Terminology
Sleep deprivation vs sleep restriction
Reviews differentiate between having no sleep over a short-term period, such as one night, and having less than required sleep over a longer period. Sleep deprivation was seen as more impactful in the short term, but sleep restriction had similar effects over a longer period. A 2022 study found that in most cases the changes induced by chronic or acute sleep loss waxed or waned across the waking day.Sleep debt
refers to a build up of lost optimum sleep. Sleep deprivation is known to be cumulative. This means that the fatigue and sleep one lost as a result of, for example, staying awake all night, would be carried over to the following day. Not getting enough sleep for a couple of days cumulatively builds up a deficiency and causes symptoms of sleep deprivation to appear. A well-rested and healthy individual will generally spend less time in the REM stage of sleep. Studies have shown an inverse relationship between time spent in the REM stage of sleep and subsequent wakefulness during waking hours. Short-term insomnia can be induced by stress or when the body experiences changes in environment and regimen.Insomnia
is a sleep disorder where people have difficulty falling asleep, or staying asleep for as long as desired. Insomnia may be a factor in causing sleep deprivation. There are three different types of insomnia:- Transient insomniashort-term sleep problems that last less than three weeks;
- Acute insomniasleep problems which last ;
- Chronic insomniasleep problems which last for at least 3months and which happen at least 3nights per week.
Health effects of sleep deprivation
Cognitive and neurobehavioral effects
Cognitive function depends heavily on adequate sleep, particularly in the prefrontal cortex, which controls executive functions like reasoning, decision-making, and attention. In a study conducted in 2010, researchers were able to identify the declines in complex cognitive processes after just a single night of sleep deprivation. Participants displayed slower reaction times, impaired logical reasoning, and reduced cognitive flexibility. All of these dysfunctions can be attributed to diminished prefrontal activation. Neuroimaging studies also confirmed similar patterns: sleep-deprived brains show reduced glucose metabolism in regions critical for alertness and attentional control.One study suggested, based on neuroimaging, that 35 hours of total sleep deprivation in healthy controls negatively affected the brain's ability to put an emotional event into the proper perspective and make a controlled, suitable response to the event.
According to the latest research, lack of sleep may cause more harm than previously thought and may lead to the permanent loss of brain cells. The negative effects of sleep deprivation on alertness and cognitive performance suggest decreases in brain activity and function. These changes primarily occur in two regions: the thalamus, a structure involved in alertness and attention, and the prefrontal cortex, a region subserving alertness, attention, and higher-order cognitive processes. Interestingly, the effects of sleep deprivation appear to be constant across "night owls" and "early birds", or different sleep chronotypes, as revealed by fMRI and graph theory.
A 2009 review found that sleep loss had a wide range of cognitive and neurobehavioral effects including unstable attention, slowing of response times, decline of memory performance, reduced learning of cognitive tasks, deterioration of performance in tasks requiring divergent thinking, perseveration with ineffective solutions, performance deterioration as task duration increases; and growing neglect of activities judged to be nonessential.
Attention
The affects of inadequate sleep extend to learning, memory, and attention. Deficits in attention and working memory are one of the most important; such lapses in mundane routines can lead to unfortunate results, from forgetting ingredients while cooking to missing a sentence while taking notes. Performing tasks that require attention appears to be correlated with the number of hours of sleep received each night, declining as a function of hours of sleep deprivation. Working memory is tested by methods such as choice-reaction time tasks.A 2009 review found that sleep loss had a wide range of cognitive and neurobehavioral effects including unstable attention, slowing of response times, decline of memory performance, reduced learning of cognitive tasks, deterioration of performance in tasks requiring divergent thinking, perseveration with ineffective solutions, performance deterioration as task duration increases; and growing neglect of activities judged to be nonessential. A study in 2025 found that just after 24 hours of sleep deprivation in healthy participants caused significant decreases in attentional processing, increased reaction times, and reduced focus. The sleep-deprived participants also exhibited difficulty switching between tasks, or disrupted cognitive flexibility, an important skill for problem-solving.
Attentional lapses also extend into more critical domains in which the consequences can be life or death; car crashes and industrial disasters can result from inattentiveness attributable to sleep deprivation. To empirically measure the magnitude of attention deficits, researchers typically employ the psychomotor vigilance task, which requires the subject to press a button in response to a light at random intervals. Failure to press the button in response to the stimulus is recorded as an error, attributable to the microsleeps that occur as a product of sleep deprivation.
Crucially, individuals' subjective evaluations of their fatigue often do not predict actual performance on the PVT. While totally sleep-deprived individuals are usually aware of the degree of their impairment, lapses from chronic sleep deprivation can build up over time so that they are equal in number and severity to the lapses occurring from total sleep deprivation. Chronically sleep-deprived people, however, continue to rate themselves considerably less impaired than totally sleep-deprived participants. Since people usually evaluate their capability on tasks like driving subjectively, their evaluations may lead them to the false conclusion that they can perform tasks that require constant attention when their abilities are in fact impaired.