Primary sleep disorders are most common in men and women over the age of 65. About half of the people claim to have some sleep problem at one point. It is most common in the elderly because of multiple factors. Factors include increased medication use, age-related changes in circadian rhythms, environmental and lifestyle changes  and pre diagnosed physiological problems and stress. The risk of developing sleep disorders in the elderly is especially increased for sleep disordered breathing, periodic limb movements, lestless legs syndrome, REM sleep behavior disorders, insomnia and circadian rhythm disturbances.
Another systematic review noted 7-16% of young adults suffer from delayed sleep phase disorder. This disorder reaches peak prevalence when people are in their 20s. Between 20 and 26% of adolescents report a sleep onset latency of >30 minutes. Also, 7-36% have difficulty initiating sleep. Asian teens tend to have a higher prevalence of all of these adverse sleep outcomes than their North American and European counterparts.
Sleep apnea, obstructive sleep apnea, obstruction of the airway during sleep, causing lack of sufficient deep sleep, often accompanied by snoring. Other forms of sleep apnea are less common. Obstructive sleep apnea (OSA) is a medical disorder that is caused by repetitive collapse of the upper airway (back of the throat) during sleep. For the purposes of sleep studies, episodes of full upper airway collapse for at least ten seconds are called apneas
The natural internal clock that controls our 24-hour cycle of sleep and waking, circadian rhythms are easily upset by changes in schedule, and they're greatly affected by light and darkness. Jet lag is the best known circadian rhythm disorder, but this sensitive inner clock can also be disrupted by changes in routine resulting in an erratic sleep schedule.