Sleep deprivation

Sleep deprivation is linked to various adverse health outcomes, including cognitive impairments, mood disturbances, and increased risk for chronic conditions.

[8] A complete absence of sleep over a long period is not frequent in humans (unless they have fatal insomnia or specific issues caused by surgery); it appears that brief microsleeps cannot be avoided.

[43] 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 (PVT), which requires the subject to press a button in response to a light at random intervals.

[46] People who drove after being awake for 17–19 hours performed worse than those with a blood alcohol level of 0.05 percent, which is the legal limit for drunk driving in most western European countries and Australia.

Another study suggested that performance begins to degrade after 16 hours awake, and 21 hours awake was equivalent to a blood alcohol content of 0.08 percent, which is the blood alcohol limit for drunk driving in Canada, the U.S., and the U.K.[47] The fatigue of drivers of goods trucks and passenger vehicles has come to the attention of authorities in many countries, where specific laws have been introduced with the aim of reducing the risk of traffic accidents due to driver fatigue.

[citation needed] Adolescents who experience less sleep show a decreased willingness to engage in sports activities that require effort through fine motor coordination and attention to detail.

[51][52] Astronauts have reported performance errors and decreased cognitive ability during periods of extended working hours and wakefulness, as well as sleep loss caused by circadian rhythm disruption and environmental factors.

[53] Deficits in attention and working memory are one of the most important;[8] such lapses in mundane routines can lead to unfortunate results, from forgetting ingredients while cooking to missing a sentence while taking notes.

In one study, subjects reported increased sleepiness, fatigue, confusion, tension, and total mood disturbance, which all recovered to their baseline after one to two full nights of sleep.

In contrast, the maintenance of wakefulness test (MWT) also uses sleep latency, but this time as a measure of the capacity of the participants to stay awake (when asked to) instead of falling asleep.

The organization recommends healthy sleep habits for ideal cardiac health, along with other well-known factors like blood pressure, cholesterol, diet, glucose, weight, smoking, and physical activity.

[83] The United Kingdom Biobank studied nearly 500,000 adults who had no cardiovascular disease, and the subjects who slept less than six hours a day were associated with a 20 percent increase in the risk of developing myocardial infarction (MI) over a seven-year follow-up period.

The team, led by Professor Cohen of Carnegie Mellon University in the United States, found that even a slight disturbance of sleep may affect the body's response to the cold virus.

[citation needed] People who are sleep deprived in general also do not provide their bodies with sufficient time for an adequate immunological memory to form and, thus, can fail to benefit from vaccination.

[92] In rats, prolonged, complete sleep deprivation increased both food intake and energy expenditure, with a net effect of weight loss and ultimately death.

[117] Similarly, light exposure, particularly from artificial sources like screens, interferes with the body’s natural circadian rhythms by suppressing melatonin production, making it challenging to fall asleep.

[119] To mitigate the effects of these environmental influences, individuals can consider strategies, such as using soundproofing measures, installing blackout curtains, adjusting room temperatures,[120] investing in comfortable bedding, and improving air quality with purifiers.

[121][122][123] Many of its symptoms are easily recognizable, including excessive daytime sleepiness; frustration or worry about sleep; problems with attention, concentration, or memory; extreme mood changes or irritability; lack of energy or motivation; poor performance at school or work; and tension headaches or stomach aches.

[144] Studies of later start times in schools have consistently reported benefits to adolescent sleep, health, and learning using a wide variety of methodological approaches.

[155] Sleep deprivation is even more severe in ICU patients, where the naturally occurring nocturnal peak of melatonin secretion was found to be absent, possibly causing the disruption in the normal sleep-wake cycle.

[158] Another study conducted on 435 non-medical staff at King Saud University Medical City reported that 9 out of 10 of the respondents used their smartphones at bedtime, with social media being the most used service (80.5%).

[167][168][169][170] Wearable devices such as Fitbits and Apple Watches monitor various body signals, including heart rate, skin temperature, and movement, to provide information about sleep patterns.

[180] A comprehensive evaluation of the human metabolome in sleep deprivation in 2014 found that 27 metabolites are increased after 24 waking hours and suggested serotonin, tryptophan, and taurine may contribute to the antidepressive effect.

This pursuit aimed both to produce a "super soldier" able "to go for a minimum of seven days without sleep, and in the longer term perhaps at least double that time frame, while preserving high levels of mental and physical performance", and to enhance productivity in sleep-deprived personnel.

Crary highlights how constant illumination and the removal of day-night distinctions create what he defines as a "time of indifference," utilizing light management as a form of psychological control.

Personnel surveys reveal common challenges such as inadequate sleep, fatigue, and impaired daytime functioning, impacting operational effectiveness and post-deployment reintegration.

The Navy, particularly influenced by retired Captain John Cordle, has actively experimented with watch schedules to align shipboard life with sailors' circadian needs, leading to improved sleep patterns, especially in submarines, supported by ongoing research efforts at the Naval Postgraduate School.

[188][189] In addition to sleep deprivation, circadian misalignment, as commonly experienced by submarine crews, causes several long-term health issues and a decrease in cognitive performance.

"[204] National Geographic Magazine has reported that the demands of work, social activities, and the availability of 24-hour home entertainment and Internet access have caused people to sleep less now than in premodern times.