Sleep is an indispensable part of human life; the fact that humans sleep for approximately one-third of the time is an index of its importance for healthy physiology. Sleep deprivation has been shown to negatively affect psychological factors, mental and physical performance, alertness, reaction time, capacity for prolonged exercise, and memory [1], [2] and [3]. Additionally, inadequate sleep is associated with an increased risk of several conditions, including coronary heart disease, obesity, diabetes, and hypertension [4], [5], [6] and [7].