Association between daytime sleepiness and quality of life in outpatients with schizophrenia.

This study aimed to investigate the prevalence of daytime sleepiness (DS) and its impact on quality of life (QOL) in outpatients with schizophrenia in the maintenance phase, as well as to identify the factors associated with DS. A total of 191 outpatients with schizophrenia completed a self-administered questionnaire including questions on lifestyle, sleep habits, DS, QOL, and sleep disorders. Insomnia, DS, and QOL were evaluated by the Athens Insomnia Scale (AIS), the Epworth Sleepiness Scale (ESS), and the MOS 8-Item Short-Form Health Survey (SF-8), respectively. The prevalence of DS was assessed with two cut-off points, ESS ≥ 11 (ESS11-DS) and ESS ≥ 8 (ESS8-DS). Psychiatric symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS). Logistic regression analyses were used to identify factors associated with DS. The prevalence of ESS11-DS and ESS8-DS was 7.3% and 21.5%, respectively. Seven of eight QOL domains were reduced in the ESS11-DS group, and four of eight QOL domains were reduced in the ESS8-DS group. In both groups, the Mental Component Summary Score of the SF-8 was decreased. On logistic regression analyses, severity of insomnia was associated with both ESS11-DS and ESS8-DS. Moreover, negative symptoms were associated with ESS11-DS. Psychotropic medications were not associated with either ESS11-DS or ESS8-DS. The present findings suggest that focusing on improving insomnia, rather than reducing medication dosage, may be more important in ameliorating DS and, consequently, QOL in patients with schizophrenia in the maintenance phase.