Sleep and recovery

This chapter summarizes the knowledge on sleep and restitution. Sleep constitutes the recuperative process of the central nervous system. The use of the brain during wakefulness will lead to depletion of energy in the cortical areas locally responsible for activity. The level of depletion is monitored and sleep is initiated when critical levels are reached. The attempts to initiate sleep are perceived as sleepiness or fatigue. The ensuing sleep then actively restores brain physiology to normal levels. This also results in restored alertness, memory capacity, and mood. Also, peripheral anabolic processes (secretion of growth hormone and testosterone) are strongly enhanced and catabolic process (secretion of cortisol and catecholamines) are strongly suppressed. In the long run, reduced or impaired sleep leads to metabolic diseases, depression, burnout, and mortality. Stress and irregular hours are among the main causes of disturbed sleep.