Physiological effects
Generally, lack of sleep may result in[2][3]
* aching muscles[4]
* hallucinations[5]
* hand tremors[6]
* irritability[2]
* memory lapses or loss[7]
* severe yawning[2]
* temper [tantrum]s in children[2]
* symptoms similar to:
o Attention-deficit Hyperactivity Disorder[2]
[edit] Diabetes
A 1996 study by the University of Chicago Medical Center showed that sleep deprivation severely affects the human body's ability to metabolize glucose, which can lead to early-stage Diabetes Type 2.[8]
[edit] Effects on the brain
Sleep deprivation can adversely affect brain function.[9] A 2000 study, by the UCSD School of Medicine and the Veterans Affairs Healthcare System in San Diego, used functional magnetic resonance imaging technology to monitor activity in the brains of sleep-deprived subjects performing simple verbal learning tasks.[10] The study showed that regions of the brain's prefrontal cortex displayed more activity in sleepier subjects. Depending on the task at hand, the brain would sometimes attempt 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 lobe, 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.
A 2001 study at Chicago Medical Institute suggested that sleep deprivation may be linked to more serious diseases, such as heart disease and mental illnesses, such as psychosis and bipolar disorder.[citation needed] A 2003 Universtity of California study found that REM sleep deprivation alleviates clinical depression. Although the mechanism is unclear it is suggested that the deprivation mimics the effects of selective serotonin reuptake inhibitors (SSRI). However, the study also indicated that REM sleep was essential for blocking neurotransmitters and allowing the neurotransmitter receptors to "rest" and regain sensitivity which in turn leads to improved regulation of mood and increased learning ability. Non REM sleep may allow enzymes to repair brain cell damage caused by free radicals. High metabolic activity while awake damages the enzymes themselves preventing efficient repair. The study observed the first evidence of brain damage in rats as a direct result of sleep deprivation.[11]
Animal studies suggest that sleep deprivation increases stress hormones, which may reduce new cell production in adult brains.[12]
[edit] Effects on growth
A 1999 study[13] found that sleep deprivation resulted in reduced cortisol secretion the next day, driven by increased subsequent slow-wave sleep. Sleep deprivation was found to enhance activity on the Hypothalamic-pituitary-adrenal axis (which controls reactions to stress and regulates body functions such as digestion, the immune system, mood, sex, or energy usage) while suppressing growth hormones. The results supported previous studies, which observed adrenal insufficiency in idiopathic hypersomnia.
[edit] Effects on the healing process
A study conducted in 2005 showed that a group of rats which were deprived of REM sleep for five days had no significant effect on their ability to heal wounds, compared to a group of rats not deprived of "dream" sleep.[14] The rats were allowed deep (NREM) sleep. However, another study conducted by Gumustekin et al.[15] in 2004 showed sleep deprivation hindering the healing of burns on rats.
[edit] Impairment of ability
According to a 2000 study published in the British Medical Journal, researchers in Australia and New Zealand reported that sleep deprivation can have some of the same hazardous effects as being drunk.[16] 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 (the U.S. and U.K. set their blood alcohol limits at .08 percent). In addition, as a result of continuous muscular activity without proper rest time, effects such as cramping are much more frequent in sleep-deprived individuals. Extreme cases of sleep deprivation have been reported to be associated with hernias, muscle fascia tears, and other such problems commonly associated with physical overexertion. Beyond impaired motor skills, people who get too little sleep may have higher levels of stress, anxiety and depression, and may take unnecessary risks. According to the National Highway Traffic Safety Administration, over 100,000 traffic accidents each year in the USA alone are caused by fatigue and drowsiness.[17] A new study has shown that while total sleep deprivation for one night caused many errors, the errors were not significant until after the second night of total sleep deprivation.[18]
The response latency seem to be higher when it comes to actions regarding personal morality rather than in situations when morality is not in question. The willingness to violate a personal belief has been shown to be moderated by EQ, so people with high EQ are affected less by sleep deprivation in such situations.[19]
[edit] Obesity
Several large studies using nationally representative samples suggest that the obesity problem the United States might have as one of its causes a corresponding decrease in the average number of hours that people are sleeping.[20][21][22] The findings suggest that this might be happening because sleep deprivation could be disrupting hormones that regulate glucose metabolism and appetite.[23] The association between sleep deprivation and obesity appears to be strongest in young and middle-age adults. 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.
