Night-to-night arousal variability and interscorer reliability of arousal measurements

Study Objectives: Measurement of arousals from sleep is clinically importan t, however, their definition is not well standardized, and little data exis t on reliability. The purpose of this study is to determine factors that af fect arousal scoring reliability and night-to-night arousal variability. Design: The night-to-night arousal variability and interscorer reliability was assessed in 20 subjects with and without obstructive sleep apnea underg oing attended polysomnography during two consecutive nights. Five definitio ns of arousal were studied, assessing duration of electroencephalographic ( EEG) frequency changes, increases in electromyographic (EMG) activity and l eg movement, association with respiratory events, as well as the American S leep Disorders Association (ASDA) definition of arousals. Setting: NA Patients: NA Interventions: NA Results: Interscorer reliability varied with the definition of arousal and ranged from an Intraclass correlation (ICC) of 0.19 to 0.92. Arousals that included increases in EMG activity or leg movement had the greatest reliabi lity, especially when associated with respiratory events (ICC 0.76 to 0.92) . The ASDA arousal definition had high interscorer reliability (ICC 0.84). Reliability was lowest for arousals consisting of EEG changes lasting <3 se conds (ICC 0.19 to 0.37). The within subjects night-to-night arousal variab ility was low for all arousal definitions. Conclusion: In a heterogeneous population, interscorer arousal reliability is enhanced by increases in EMG activity, leg movements, and respiratory ev ents and decreased by short duration EEG arousals. The arousal index night- to-night variability was low for all definitions.