Study Objectives: Patients with circadian rhythm sleep disorders (CRSDs) often have coincidence of orthostatic dysregulation (OD). Both disorders have many common clinical features. However, the prevalence of OD in patients with CRSD has not been examined. Methods: Thirty-eight patients with CRSD with either delayed sleep phase disorder or free-running disorder were tested for OD using the new orthostatic test, which was originally established by Tanaka et al. (< 20 years) and the Schellong test, i.e., the active standing test (≥ 20 years). Results:The overall prevalence of OD in patients with CRSD was 57.9% (22/38), and prevalence of OD was 70% in patients under 20 years of age (14/20). These rates exceed the previously reported values in adolescents aged 14-15 years (15%), regarded as the age with highest OD prevalence. Prevalence was not significantly associated with CRSD severity and medications used. Conclusions:We observed a high prevalence of OD in patients with CRSD, suggesting some relationship between CRSD and OD. Large-scale case-control studies are warranted to investigate the underlying mechanisms for this comorbidity. I NTRO DUCTI O NCircadian rhythm sleep disorders (CRSDs) are characterized by persistent or recurrent patterns of sleep disturbance pri marily caused by alterations in the circadian timing system or misalignment between the endogenous circadian rhythm and external schedules. CRSD is associated with impairments in social, occupational, and other areas of functioning.1 Delayed sleep phase disorder (DSPD) is the most common CRSD diag nosis (excluding shift work disorder and jet lag disorder), with a prevalence of 0.1% to 0.4%.2,3 DSPD is more common among adolescents and young adults. Many of these schoolage pa tients often have school refusal; sometimes it is difficult to dis tinguish clinically whether school refusal is a cause or a result of the circadian rhythm disturbance. Previous studies reported that the nadir of core body temperature (CBT) was markedly delayed, and that the amplitude of circadian CBT rhythm was significantly smaller in subjects with school refusal behavior than in healthy controls. 4,5 These observations suggest that the clinical psychosomatic symptoms often observed in patients with school refusal behavior are related to the desynchroniza tion of the circadian rhythm of body temperature and sleep wake rhythm. 4,5 It is our clinical experience that patients with CRSD often have a diagnosis of orthostatic dysregulation (OD), a functional physical disorder with an impairment of circulatory adjustment against gravitational stress because of dysregulation of the au tonomic nervous system. 6,7 OD is common in adolescents and often affected by psychosocial factors; therefore, it is regarded as a psychosomatic disorder. The characteristics of OD among adults, alternatively named as orthostatic intolerance (OI) in America and Europe, has not been as clearly defined as those of OD among children. 8,9 It was reported that more than half of the Japanese children with sym...

A sleep diary is often employed for diagnosing and treating hypersomnia. However, its reliability needs to be evaluated because overlooked chronic sleep insufficiency could be misdiagnosed as narcolepsy. In this study, we compared simultaneous sleep measurements using a sleep diary and by actigraphy in patients visiting our sleep clinic for the first time with complaints of excessive daytime sleepiness. Of the 28 patients enrolled, 24 complied with both these requirements. In this population, the results obtained using a sleep diary tended to estimate a statistically significant earlier sleep onset time and longer total sleep time than those via actigraphy. For total sleep time, this tendency was more prominent in patients with a higher Epworth Sleepiness Scale score. In 5 of the 24 (20.8%) patients, the sleep diary records indicated >6 h of total sleep time while the actigraphy records indicated <6 h of total sleep time, with a discrepancy of >1 h. These results suggested that sleep insufficiency in hypersomnia patients may be overlooked when their sleep time is assessed using only a sleep diary in the initial phase of the diagnostic procedure, and the simultaneous use of actigraphy may be preferable in this assessment.

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