Genetics of Central Disorders of Hypersomnolence

Central disorders of hypersomnolence (CDH) are characterized by a primary complaint of excessive daytime sleepiness (EDS) not attributable to another sleep disorder disturbing nocturnal sleep (e.g., obstructive sleep apnea), insufficient sleep, and/or circadian dysrhythmias. EDS represents the common background feature of these disorders which have different pathophysiology and clinical features. Due to dysfunction of the central nervous system, CDH impairs daily functions. Familial cases of EDS have been widely seen indicating genetic influence on these sleep disorders with hypersomnia. Great effort has been put to find biomarkers of CDH and it is well recognized the genetic variations affect the timing of sleep, duration of sleep, and EEG patterns. In this review, we specifically focused on a group of central disorders such as narcolepsy, idiopathic hypersomnia, and Kleine-Levin syndrome. This section will provide a detailed background on the genetics of these disorders.