Sleep deprivation

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Sleep deprivation is an overall lack of the necessary amount of sleep. A person can be deprived of sleep by their own body and mind, insomnia, or actively deprived by another individual. Sleep deprivation is sometimes used as an instrument of torture, but it has also been shown to be an effective treatment of depression and other mental illnesses as well. Sleep deprivation afflicts 47 million adults in the United States]].

Lack of sleep may also result in irritability, blurred vision, slurred speech, memory lapses, overall confusion, hallucinations, nausea, psychosis.

Failure to sleep results in progressively severe psychological and physical distress. In 1965, California teenager Randy Gardner attempted to resist sleep in an uncontrolled "experiment". As his ordeal progressed he fell into a silent stupor, bringing into doubt whether he was actually awake in any practical sense. There are occasional stories of people who are able to function with a small or no amount of sleep, in many cases due to brain damage brought on by an accident, but these cases do not appear to hold up under controlled conditions.

A study at the University of Pittsburgh School of Medicine showed that poor sleep and sleep deprivation in older adults can lead to earlier death, but another survey of more than a million people in the 1980s found that those who slept more than seven and a half hours tended to die a little earlier. It is difficult to perform such studies as controlled experiments, since persons with various physical and psychological problems may be inclined to sleep longer as a result of these illnesses. For example, long sleepers tend to have a higher than average rate of sleep disorders, possibly artificially increasing their reported sleep time, and providing a statistical selection effect that undermines the validity of many such studies.

A 1999 University of Chicago team led by Eve Van Cauter limited a group of lean young men to four hours of sleep per night for 16 days. The subjects showed decreased levels of leptin and increased levels of cortisol. The subjects also increased their daily caloric intake by 1,000 calories. The team discovered that the subjects' insulin and blood sugar levels resembled the impaired glucose tolerance of prediabetics, an indication that they were no longer properly processing carbohydrates. Studies have also linked sleep deprivation to an increased incidence of obesity.

At Harvard Medical School, researchers have identified associations between sleep deprivation and illnesses ranging from hypertension and heart attacks to cancer. Poor sleepers generate increased levels of stress hormones and show more inflammatory changes in the walls of their small blood vessels, both of which contribute to elevated blood pressure. Because of their exposure to light at night, night-shift workers produce less melatonin, a hormone which not only promotes sleep but has been shown to have cancer-prevention benefits as well.

Despite the risks, sleeping less is attractive to some because of the additional time made available, and many people feel they have to sleep less to maintain their lifestyle. They may resort to trying polyphasic sleep, a method for minimizing the time spent asleep, while maximizing its effects. This is done by sleeping in short naps throughout the day, minimizing the time spent awake between periods of sleep and thus decreasing the workload of the brain while sleeping. People who take so-called power naps during the day are practicing a variation of polyphasic sleeping. In this regard, cultures where the siesta is customary are also taking advantage of alternative means of obtaining sufficient sleep.

Experiments with rats have been designed to measure the effects of severe sleep deprivation. In one, a pair of rats were placed on a platform and separated by a movable wall. Both were instrumented with electroencephalograms. Whenever the "subject" rat began to show signs of sleep the partition was moved, forcing both rats to move. The "control" rat, however, was allowed to sleep in between movements. After several weeks the "subject" rat became unable to regulate body temperature; even if allowed to sleep at this point, it died shortly afterward from septic shock.

Some recent studies concluded the cause of death in the rat experiments to be more closely related to REM deprivation, but also found the rats died in about a week less time. It is believed this is because, unlike non-REM sleep that repairs parts of the brain damaged by metabolism and free radicals, REM sleep repairs the repair center. It is unclear the degree to which the results of sleep deprivation in rats can be generalized to humans.

In sleep-deprived states less extreme than that suffered by Randy Gardner, humans display irritability, impaired cognitive function, and poor judgment. Experiments on sleep-deprived medical trainees, for example, have shown them less able to interpret EKGs and x-rays than their well rested peers. As late as early 21st century people thought that too little sleep could be negated by "paying back the sleep debt". However, recent studies have shown this to be false. After extensively prolonged period of awareness, average humans can sleep comfortably for as long as 14 hours in row, but any amount over that has no effect for health. Sleeping over it causes dizziness, lack of muscular control, numbness and several other symptoms often confronted with too little sleep.

That one major function of sleep is consolidation and optimization of memories (including "unlearning") is evidenced by studies showing that mental functions are impaired by sleep deprivation and that sleep deprivation can even be lethal. Adequate rest and a properly functioning immune system are closely related. Sleep deprivation compromises the immune system by altering the blood levels of specialized immune cells and important proteins called cytokines, resulting in an increased chance of infection. We may begin to understand why sleep deprivation is lethal if we understand sleep as a necessary period of anabolic activity for all animals, and the basic need for anabolic activity as a prerequisite for life itself.

As a cause of death

There are a number of claims linking the lack of sleep to premature death, but these claims require scientific evidence before they can be verified.  As it stands, there is little-to-no evidence that complete deprivation of sleep in humans will cause death:

• Total sleep deprivation in rats leads to death in around 28 days. Death occurs later if only REM or only NREM sleep are eliminated.
• A person who has fatal familial insomnia may die after several months with no sleep at all; people without this condition may experience dementia or develop permanent personality changes within the first few weeks.
• In some rare cases, however, people have gone for months - or even years - without sleep, with limited or no adverse side effects.

As a cause of diabetes

A 1999 study by the University of Chicago Medical Center shows that sleep deprivation severely affects the human body's ability to metabolize glucose, which can lead to early-stage diabetes.

Effects on the brain

A 2000 study by the UCSD School of Medicine and the Veterans Affairs Healthcare System in San Diego, used functional magnetic resonance imaging (fMRI) technology to monitor activity in the brains of sleep-deprived subjects performing simple verbal learning tasks. The study showed that regions of the brain’s prefrontal cortex (PFC) displayed more activity in sleepier subjects. Depending on the task at hand, in some cases the brain attempts to compensate for the adverse effects caused by lack of sleep. The temporal lobe, which is a brain region involved in language processing, was activated during verbal learning in rested subjects but not in sleep deprived subjects. The parietal lobes, not activated in rested subjects during the verbal exercise, was more active when the subjects were deprived of sleep. Although memory performance was less efficient with sleep deprivation, greater activity in the parietal region was associated with better memory.

The British television reality show Shattered aired in 2004, in which contestants had to endure seven days with very little sleep. The effects of sleep deprivation on the brain were captured on 24/7 cameras. The show is considered the most well known sleep deprivation experiment to date.

Effects on growth

According to a study by Alexandros N. Vgontzas, George Mastorakos, Edward O. Bixler, Anthony Kales, Philip W. Gold & George P. Chrousos, published in Clinical Endocrinology, Volume 51 Issue 2 Page 205, August 1999:

Sleep deprivation results in a significant reduction of cortisol secretion the next day and this reduction appears to be, to a large extent, driven by the increase of slow wave sleep during the recovery night. Deep sleep has an inhibitory effect on the HPA axis while it enhances the activity of the GH axis. In contrast, sleep disturbance has a stimulatory effect on the HPA axis and a suppressive effect on the GH axis. These results are consistent with the observed hypocortisolism in idiopathic hypersomnia and HPA axis relative activation in chronic insomnia. Finally, our findings support previous hypotheses about the restitution and immunoenhancement role of slow wave (deep) sleep.

Impairment of ability

According to a 2000 study published in the British scientific journal Occupational and Environmental Medicine, researchers in Australia and New Zealand reported that sleep deprivation can have some of the same hazardous effects as being drunk. Getting less than 6 hours a night can affect coordination, judgment and reaction time. People who drove after being awake for 17–19 hours performed worse than those with a blood alcohol level of .05 percent, which is the legal limit for drunk driving in most western European countries (most U.S. states set their blood alcohol limits at .08 percent). The study stated that 16 to 60 percent of road accidents involve sleep deprivation. Beyond impaired motor skills, people who get too little sleep may have higher levels of stress, anxiety and depression, and may take unnecessary risks.

As a cause of obesity

A 2005 large study of a nationally representative sample of about 10,000 adults, suggested that the U.S.' obesity epidemic might have as one of its causes a corresponding decrease in the average number of hours that Americans are sleeping. Some scientists speculate that this might be happening because sleep deprivation might be disrupting hormones that regulate appetite. The study found that people between the ages of 32 and 49 who sleep less than 7 hours a night are significantly more likely to be obese. Other scientists hold that the physical discomfort of obesity and related problems, such as sleep apnea, reduce an individual's chances of getting a good night's sleep.

As a treatment for depression

Recent studies show sleep deprivation has some potential in the treatment of depression. 60% of patients, when sleep-deprived, show immediate recovery, with most relapsing the following night. The incidence of relapse can be decreased by combining sleep deprivation with medication [1]. Incidentally, many tricyclic antidepressants happen to suppress REM sleep, providing additional evidence for a link between mood and sleep [2].

Prevention of effects in soldiers

Since sleep deprivation is a fact of modern combat, the U.S. army, through DARPA, has a "Preventing Sleep Deprivation Program", which has the goal to prevent the harmful effects of sleep deprivation and provide methods for recovery of function with particular emphasis on cognitive and psychomotor impairments. Their efforts include new pharmaceuticals that enhance neural transmission, nutraceuticals that promote neurogenesis, cognitive training, and devices such as transcranial magnetic stimulation.

The United States Military has recently begun to explore the use of a new drug called modafinil, which has prevented the negative effects of sleep deprivation in soldiers. Modafinil may increase wakefulness through activation of noradrenergic and dopaminergic systems, possibly through interaction with the hypocretin/orexin system PMID 15532213 .

See also

• Sleep debt
• Randy Gardner - World record holder for the longest time a human being has ever stayed awake.
• Polyphasic Sleep

See also

• Sleep disorders

Key texts

Papers

• Vogel, G.W. (1975) A review of REM sleep deprivation, Archives of General Psychiatry 32: 749-61
• Gillin, J.C., Buchsbaum, M.S. and Jacobs, L.S. (1974) Partial REM sleep deprivation, schizophrenia and field articulation, Archives of General Psychiatry 30:653-62.

Additional material

Papers

• Google Scholar

External links

• National Sleep Foundation 2005 Sleep in America Poll (from the National Sleep Foundation)
• Brain activity is visibly altered following sleep deprivation
• Sleep deprivation effects on the activity of the hypothalamic–pituitary–adrenal and growth axes: potential clinical implications, by Alexandros N. Vgontzas, George Mastorakos, Edward O. Bixler, Anthony Kales, Philip W. Gold & George P. Chrousos
• Why Do Humans and Many Other Animals Sleep?
• Microsleep during partial sleep deprivation in depression.
• Sleep Disorder Treatments