“Sleep is the golden chain that ties health and our bodies together.”
Thomas Dekker (1572-1632)

SLEEP. A natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, there is a decrease in bodily movement, responsiveness to external stimuli, an increased rate of anabolism (the synthesis of cell structures), and a decreased rate of catabolism (the breakdown of cell structures). Sleep is a time for the body‘s revitalization that helps meet the demands of the waking hours.

Quantity of sleep
Different people sleep for different lengths of time. For some, 4 hours a night is adequate to function normally. Others require as much as 10 hours each night. The average is around 7.5 hours.

Functions of sleep
While we sleep, our pituitary gland releases large amounts of growth hormone. This amount peaks at about one hour after falling asleep and gradually decreases towards dawn. So, sleep seems to be a state marked by physiological processes of growth and rejuvenation of the organism‘s immune, nervous, muscular, and skeletal systems. During sleep, the body‘s metabolic rate decreases, allowing it to conserve energy to support our busy lifestyles and overall health.
There is also evidence that sleep restores mental alertness and memory. When you sleep, portions of your brain shut down or lower their activity rates. This is advantageous because your brain uses chemical neurotransmitters to send messages along neurons. Sleep allows these neurotransmitters to be replenished so you can think clearly and quickly. A comparison might be to pouring new oil in a car to keep it running smoothly.
All in all, sleep is necessary for physiological and mental health. That is why the problems and damages of deprivation of sleep or the lack of relaxation in sleep are numerous and have far-reaching consequences.

Sleep disorders
Suffering from a sleep disorder or non-restorative sleep can bring about multiple negative consequences: affected concentration and working capacities, limited perception, indisposition, nervousness, and irritability. In the long term, a sleep disorder can even lead to depression and hallucinations. Being well rested and relaxed not only affects the subjective sense of well-being but also the social capacity and strength, in the family, with friends, and in professional life.