Transitions in effective scaling behavior of accelerometric time series across sleep and wake

¹ Institut für Physik, Martin-Luther-Universität - von-Seckendorff-Platz 1, 06099 Halle (Saale), Germany, EU
² Institut für Klinische Epidemiologie, Martin-Luther-Universität, Magdeburger Str. 8, 06097 Halle (Saale), Germany, EU
³ Complexity Science Group, Department of Physics and Astronomy, University of Calgary 2500 Univ. Dr. NW, Calgary, Canada
⁴ Schlafmedizinisches Zentrum, Charité - Universitätsmedizin Berlin - Luisenstraße 13a, 10117 Berlin, Germany, EU
⁵ Klinik und Poliklinik für Psychiatrie, Psychotherapie und Psychosomatik, Martin-Luther-Universität Halle, Germany, EU

^(a) patrick.wohlfahrt@mailbox.tu-dresden.de
^(b) jan.kantelhardt@physik.uni-halle.de
^(c) melanie.zinkhan@uk-halle.de
^(d) ay.schumann@ucalgary.ca
^(e) thomas.penzel@charite.de
^(f) ingo.fietze@charite.de
^(g) frank.pillmann@medizin.uni-halle.de
^(h) andreas.stang@uk-halle.de

Received: 27 June 2013
Accepted: 9 September 2013

Abstract

We study the effective scaling behavior of high-resolution accelerometric time series recorded at the wrists and hips of 100 subjects during sleep and wake. Using spectral analysis and detrended fluctuation analysis we find long-term correlated fluctuations with a spectral exponent ( noise). On short time scales, β is larger during wake () and smaller during sleep (). In addition, characteristic peaks at 0.2–0.3 Hz (due to respiration) and 4–10 Hz (probably due to physiological tremor) are observed in periods of weak activity. Because of these peaks, spectral analysis is superior in characterizing effective scaling during sleep, while detrending analysis performs well during wake. Our findings can be exploited to detect sleep-wake transitions.