Circadian rhythm sleep disorders are characterized by the abnormal timing of the major sleep period that results in complaints of insomnia and excessive daytime sleepiness. Evidence suggests that these disorders are the result of alterations in the circadian timing system [57,62,118] and potentially in the sleep homeostatic process at least for DSPS patients [28,29] and age-related advanced sleep phase. It is also clear that some of these disorders are familial in nature and may be the result of alterations in the function of circadian clock genes [57,58,62,63]. Treatments are limited for these disorders because of a lack of practical diagnostic tools to assess circadian function, and randomized controlled clinical trials. Further studies of the pathophysiology of circadian rhythm sleep disorders are necessary for the development of improved treatments.
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