Decreased sleep stage transition pattern complexity in narcolepsy type 1

Objective To analyze the complexity of the nocturnal sleep stage sequence in central disorders of hypersomnolence (CDH), with the hypothesis that narcolepsy type 1 (NT1) might exhibit distinctive sleep stage sequence organization and complexity. Methods Seventy-nine NT1 patients, 22 narcolepsy type 2 (NT2), 22 idiopathic hypersomnia (IH), and 52 patients with subjective hypersomnolence (sHS) were recruited and their nocturnal sleep was polysomnographically recorded and scored. Group between-stage transition probability matrices were obtained and compared. Results Patients with NT1 differed significantly from all the other patient groups, the latter, in turn, were not different between each other. The individual probability of the R-to-N2 transition was found to be the parameter showing the difference of highest significance between the groups (lowest in NT1) and classified patients with or without NT1 with an accuracy of 78.9% (sensitivity 78.5% and specificity 79.2%), by applying a cut-off value of 0.15. Conclusions The main result of this study is that the structure of the sleep stage transition pattern of hypocretin-deficient NT1 patients is significantly different from that of other forms of CDH and sHS, with normal hypocretin levels. Significance The lower probability of R-to-N2 transition occurrence in NT1 appears to be a reliable polysomnographic feature with potential application at the individual level, for supportive diagnostic purposes.