title: Automatic detection of wakefulness and rest intervals in actigraphic signals: a data-driven approach.
abstract: Actigraphy is an useful tool for evaluating the activity pattern of a subject; activity registries are usually processed by first splitting the signal into its wakefulness and rest intervals and then analyzing each one in isolation. Consequently, a preprocessing stage for such a splitting is needed. Several methods have been reported to this end but they rely on parameters and thresholds which are manually set based on previous knowledge of the signals or learned from training. This compromises the general applicability of this methods. In this paper we propose a new method in which thresholds are automatically set based solely on the specific registry to be analyzed. The method consists of two stages: (1) estimation of an initial classification mask by means of the expectation maximization algorithm and (2) estimation of a final refined mask through an iterative method which re-estimates both the mask and the classifier parameters at each iteration step. Results on real data show that our methodology outperforms those so far proposed and can be more effectively used to obtain derived sleep quality parameters from actigraphy registries.
authors.affiliation: Laboratorio de Procesado de Imagen, Universidad de Valladolid, Valladolid, Spain. Electronic address: dmarmar@lpi.tel.uva.es.
authors.forename: D
authors.initials: D
authors.lastname: Martín-Martínez
authors.affiliation: Audio Visual Communications and Networking Research Centre, University of the West of Scotland, Paisley, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Casaseca-de-la-Higuera
authors.affiliation: Laboratorio de Procesado de Imagen, Universidad de Valladolid, Valladolid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Andrés-de-Llano
authors.affiliation: Laboratorio de Procesado de Imagen, Universidad de Valladolid, Valladolid, Spain.
authors.forename: J R
authors.initials: JR
authors.lastname: Garmendia-Leiza
authors.affiliation: Laboratorio de Procesado de Imagen, Universidad de Valladolid, Valladolid, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Alberola-López
authors.affiliation: Laboratorio de Procesado de Imagen, Universidad de Valladolid, Valladolid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Alberola-López
mesh_terms: D056044:Actigraphy / Q000379:methods*; D000465:Algorithms; D002648:Child; D006801:Humans; D016011:Normal Distribution; D010363:Pattern Recognition, Automated / Q000379:methods*; D012146:Rest; D012815:Signal Processing, Computer-Assisted; D018709:Statistics, Nonparametric; D014851:Wakefulness
keywords: Actigraphy; Expectation–maximization algorithm; Probability density function; Wakefulness/Rest detection