title: The addition of entropy-based regularity parameters improves sleep stage classification based on heart rate variability.
abstract: The work considers automatic sleep stage classification, based on heart rate variability (HRV) analysis, with a focus on the distinction of wakefulness (WAKE) from sleep and rapid eye movement (REM) from non-REM (NREM) sleep. A set of 20 automatically annotated one-night polysomnographic recordings was considered, and artificial neural networks were selected for classification. For each inter-heartbeat (RR) series, beside features previously presented in literature, we introduced a set of four parameters related to signal regularity. RR series of three different lengths were considered (corresponding to 2, 6, and 10 successive epochs, 30 s each, in the same sleep stage). Two sets of only four features captured 99 % of the data variance in each classification problem, and both of them contained one of the new regularity features proposed. The accuracy of classification for REM versus NREM (68.4 %, 2 epochs; 83.8 %, 10 epochs) was higher than when distinguishing WAKE versus SLEEP (67.6 %, 2 epochs; 71.3 %, 10 epochs). Also, the reliability parameter (Cohens's Kappa) was higher (0.68 and 0.45, respectively). Sleep staging classification based on HRV was still less precise than other staging methods, employing a larger variety of signals collected during polysomnographic studies. However, cheap and unobtrusive HRV-only sleep classification proved sufficiently precise for a wide range of applications.
authors.affiliation: Dipartimento di Informatica, Università degli Studi di Milano, Crema, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Aktaruzzaman
authors.forename: M
authors.initials: M
authors.lastname: Migliorini
authors.forename: M
authors.initials: M
authors.lastname: Tenhunen
authors.forename: S L
authors.initials: SL
authors.lastname: Himanen
authors.forename: A M
authors.initials: AM
authors.lastname: Bianchi
authors.forename: R
authors.initials: R
authors.lastname: Sassi
mesh_terms: D000328:Adult; D004569:Electroencephalography; D019277:Entropy; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012815:Signal Processing, Computer-Assisted; D012894:Sleep Stages / Q000502:physiology*; D055815:Young Adult