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During sleep a number of vital functions to maintaining good health and allow people to function better. On the other hand, not enough sleep can be dangerous, for example, you are more likely in a car accident if you drive when you are sleepy.
We need sleep to think clearly, react quickly and create memories. In fact, the ways in the brain, which remind us and learn are very active when we sleep.
Reduction of 1 hour can make it difficult to get the next day and can slow your response time. Studies also find that if you lack of sleep, you are rather poorly to make decisions. This can lead to a decline in performance at work or at school and a greater danger to a car accident
Sleep affects mood. Insufficient sleep can be irritable and is linked to bad behavior and problems with relationships.
Sleep is also important for good health. Studies show that not enough sleep or poor sleep quality at regular intervals increases the risk of high blood pressure, heart disease and other medical conditions.
Moreover, during sleep, the body produces hormones, and help muscle mass and repair cells and tissues in children and adults. Another type of hormone increases during sleep that works to fight various infections. This may explain why a good sleep helps you hold to the sick and help you again if you become ill.
Hormones released during sleep also affect how the body uses energy. Studies found that people sleep less, the more likely they are overweight or obese, to develop diabetes, and prefers to eat foods with high calories and carbohydrates.

Part1, Part2, Part3, Part4