Setting Objective Clinical Assessment Tools for Circadian Rhythm Sleep-Wake Disorders – A Community-Based Cross-Sectional Epidemiological Study

INTRODUCTION: Circadian rhythm sleep-wake disorder (CRSWD) is an often-misdiagnosed group of sleep disturbances with limited data concerning diagnostic and therapeutic algorithms in the general population. Therefore, reported prevalence varies in the literature due to different case definitions, methodological, and environmental factors. OBJECTIVES: The purpose of our cross-sectional study was to estimate the prevalence of CRSWD in the general population of Cyprus and to suggest clinical parameters for the assessment of atypical sleep schedules. The estimation was carried out by introducing normal preset sleep time limits, according to the imposed local environment and by administering well-established questionnaires for symptoms and consequence dysfunction, as objective evaluation tools. METHODS: In a nationwide epidemiological survey, 4118 Cypriot adult participants, selected and stratified to represent the general population, were interviewed on sleep habits and complaints by computer-assisted telephone interviewing (CATI). In the second stage, 250 adults were randomly selected from the initial representative sample, for a CRSWD assessment. According to the proposed diagnostic criteria, patients were interviewed about sleepiness and/or insomnia, and daytime dysfunction (fatigue, anxiety, and depression). They were also assessed by a weekly sleep diary for sleep schedules. Finally, all participants underwent a Type III Sleep Study, to rule out obstructive sleep apnea. RESULTS: From 195 enrolled participants (response rate 78%), 25 individuals (12.8%) met the criteria for CRSWD. The two most prevalent disorders were delayed sleep-wake phase disorder (DSWPD) (10pts, 5.1%) and shift work sleep disorder (SWD) (13, 6.7%). Less prevalent disorders included irregular sleep-wake rhythm disorder (ISWRD) (1, 0.5%) and advanced sleep-wake phase disorder (ASWPD) (1, 0.5%). CONCLUSIONS: According to our data, CRSWDs are common in the general population of Cyprus, especially DSWPD and SWD. Affected individuals usually suffer from sleep deprivation and complain about insomnia, sleepiness and depression.