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Sleep Disorders
Volume 2013 (2013), Article ID 726372, 15 pages
http://dx.doi.org/10.1155/2013/726372
Research Article

A Preliminary Evaluation of the Physiological Mechanisms of Action for Sleep Restriction Therapy

1École de psychologie, Université Laval, Québec, QC, Canada G1V A06
2Centre d’étude des troubles du sommeil, Centre de recherche de l’institut universitaire en santé mentale de Québec, Québec, QC, Canada G1J 2G3
3Centre de recherche du centre hospitalier universitaire en santé mentale du Québec, Québec, QC, Canada G1V 4G2
4Nuffield Department of Clinical Neurosciences, Sleep & Circadian Neuroscience Institute, University of Oxford, Oxford OX3 9DU, UK

Received 27 June 2013; Revised 8 September 2013; Accepted 16 September 2013

Academic Editor: Marco Zucconi

Copyright © 2013 Annie Vallières et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Our objective was to investigate the physiological mechanisms involved in the sleep restriction treatment of insomnia. A multiple baseline across subjects design was used. Sleep of five participants suffering from insomnia was assessed throughout the experimentation by sleep diaries and actigraphy. Ten nights of polysomnography were conducted over five occasions. The first two-night assessment served to screen for sleep disorders and to establish a baseline for dependent measures. Three assessments were undertaken across the treatment interval, with the fifth and last one coming at follow-up. Daily cortisol assays were obtained. Sleep restriction therapy was applied in-lab for the first two nights of treatment and was subsequently supervised weekly. Interrupted time series analyses were computed on sleep diary data and showed a significantly decreased wake time, increased sleep efficiency, and decreased total sleep time. Sleepiness at night seems positively related to sleep variables, polysomnography data suggest objective changes mainly for stage 2, and power spectral analysis shows a decrease in beta-1 and -2 powers for the second night of treatment. Cortisol levels seem to be lower during treatment. These preliminary results confirm part of the proposed physiological mechanisms and suggest that sleep restriction contributes to a rapid decrease in hyperarousal insomnia.