Sleep disorders are among the most common health problems in the general population. Good sleep, i.e.
sufficiently long and of good quality, was found to be significantly associated with optimal physiological and cognitive functioning and a sense of well-being. To function optimally on a daily basis, healthy adults need about 7-8 hours of sleep a day. The quality of sleep is affected by a variety of factors, including the level of activity during the day, the duration and timing of exposure to light and levels of stress and anxiety.