Oddly enough, neither the reasons nor the evolutionary origins of sleep are known to science. From the standpoint of nature, sleep is hardly something worthwhile. If a person or animal is sleeping, his mind is ‘turned off’ for several hours. Needless to say, that in this state the chance of being eaten by predators grows significantly.
And yet, some regularities, if not reasons, of sleep were discovered by scientists. It turned out, for example, that adults who sleep 6 to 8 hours are characterized by a greater longevity. At the same time, an excess of sleep can lead to a number of diseases, including cardiovascular diseases and diabetes. But chronic sleep deprivation is associated with cardiovascular disease, depression, obesity, and even brain damage.
What will happen if you do not sleep at all? After the first sleepless night the so called mesolimbic pathway is activated in the human brain, and dopamine is released into the blood. With the help of it, a person becomes energetic, positive and active in terms of sex. Sounds good? It’s gonna be worse. First, the structures responsible for making decisions and assessing their consequences are deactivated in the brain one after another. The result is a reduction of self-control. Fatigue takes its toll, and the reaction rate slows down more and more, which leads to the fact that perception of the world is attenuated.
After two sleepless nights, the glucose metabolism and the immune system function of the human body break down. After three sleepless nights hallucinations can occur.
The most prolonged sleep deprivation within the scientific experiment lasted for 264 hours or 11 days. The experiment was interrupted for obvious reasons. But what did scientists find out? To their surprise, after 11 days without sleeping, the participant was absent-minded and irritated and found it difficult to perceive the world around him. But there were no consequences for his organism. In medical terms all the organs were working properly, there was no brain damage or mental disorders. However, it is worth remembering that the experiment was ended. Therefore, there is no guarantee that subsequently the participant’s health would not suffer irreparable harm.
Indeed, experiments in rats have shown that after two weeks of sleep deprivation the poor animals died. However, the researchers are not sure that the cause of death was lack of sleep and not the constant stress from being awake.
The study of fatal familial insomnia – a rare genetic brain disease in which a person suffers from more severe sleep disorders – may shed light on this issue. In fact, the patient suffers from insomnia, which leads first to hallucinations, then – to the mental disorders, and then to death. Despite the fact that the number of cases of such kind of insomnia is not more than a hundred people, the average lifespan after the onset of the disease is not more than 18 months. With progression of insomnia, internal organs one after another stop working. In other words, although the lack of sleep does not result in a quick death, a prolonged sleep deprivation adversely affects the body and can even lead to death.
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