Differences in nocturnal and daytime sleep between primary and psychiatrichypersomnia: Diagnostic and treatment implications

Objective: The differential diagnosis of primary (idiopathic) vs. psychiatr ic hyparsomnia is challenging because of the lack of specific clinical or l aboratory criteria differentiating these two disorders and the frequent com orbidity of mental disorders in patients with primary hypersomnia. The aim of this study was to assess whether polysomnography aids in the differentia l diagnosis of these two disorders. Methods: After excluding patients takin g medication and those with an additional diagnosis of sleep-disordered bre athing, we compared the nocturnal and daytime sleep of 82 consecutive patie nts with a diagnosis of either primary hypersomnia (N = 59) or psychiatric hypersomnia (N = 23) and normal control subjects (N = 50). Results: During nocturnal sleep, patients with psychiatric hypersomnia showed significantly higher sleep latency, wake time after sleep onset, and total wake time and a significantly lower percentage of sleep time than patients with primary hyparsomnia and control subjects (p < .05). In addition, the daytime sleep of patients with psychiatric hypersomnia was significantly higher in terms of sleep latency, total wake time, and percentage of light (stage 1) sleep and lower in terms of percentage of sleep time and stage 2 sleep than in pa tients with primary hypersomnia and control subjects (p < .05), The daytime sleep of patients with primary hypersomnia as compared with that of contro l subjects was characterized by lower sleep latency and total wake time and a higher percentage of sleep time (p < .05). Finally, a sleep latency of l ess than 10 minutes or a sleep time percentage greater than 70% in either o f the two daytime naps was associated with a sensitivity of 78.0% and a spe cificity of 95.7%. Conclusions: Our findings indicate that psychiatric hype rsomnia is a disorder of hyperarousal, whereas primary hypersomnia is a dis order of hypoarousal. Polysomnographic measures may provide useful informat ion in the differential diagnosis and treatment of these two disorders.