Sleep is a "natural, temporary loss of consciousness" (Robinson, 1941) necessary for our bodies to build up energy reserves and regenerate body cells and tissues. During sleep, the heart beats more slowly, breathing becomes slower, growth hormones peak, muscles relax and body temperature lowers. Newborn infants sleep almost continuously, gradually decreasing their need for sleep. In early childhood, 12 to 13 hours of sleep are generally required and this amount decreases to approximately 8 hours in adulthood. After the age of 50, sleep is often characterized by frequent night time wakenings, shorter dream lengths and less overall sleep (Bricklen, 1990).
Many consider sleep to be of low priority among the many daily activities engaged in. It is estimated that the world's population is depriving itself of one less hour of sleep per night than is needed. Despite this view of night-time rest, sleep is a necessary, sophisticated process regulated by the brain. Operating as a 24- hour clock, chemical substances, such as melanin, are released in the body to trigger sleepiness.