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Sleep Disorders
Volume 2012 (2012), Article ID 404196, 6 pages
Research Article

Mood Predicts Response to Placebo CPAP

1Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
2Health Services Research & Development Service, Veterans Affairs San Diego Healthcare System, San Diego, CA 92161, USA
3Department of Psychiatry, Tri-Service General Hospital, Taipei, Taiwan
4Department of Psychiatry, University of California, San Diego, La Jolla, CA 92093, USA

Received 30 April 2012; Revised 30 July 2012; Accepted 2 August 2012

Academic Editor: Liborio Parrino

Copyright © 2012 Carl J. Stepnowsky 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.


Study Objectives. Continuous positive airway pressure (CPAP) therapy is efficacious for treating obstructive sleep apnea (OSA), but recent studies with placebo CPAP (CPAP administered at subtherapeutic pressure) have revealed nonspecific (or placebo) responses to CPAP treatment. This study examined baseline psychological factors associated with beneficial effects from placebo CPAP treatment. Participants. Twenty-five participants were studied with polysomnography at baseline and after treatment with placebo CPAP. Design. Participants were randomized to either CPAP treatment or placebo CPAP. Baseline mood was assessed with the Profile of Mood States (POMS). Total mood disturbance (POMS-Total) was obtained by summing the six POMS subscale scores, with Vigor weighted negatively. The dependent variable was changed in apnea-hypopnea index (ΔAHI), calculated by subtracting pre- from post-CPAP AHI. Negative values implied improvement. Hierarchical regression analysis was performed, with pre-CPAP AHI added as a covariate to control for baseline OSA severity. Results. Baseline emotional distress predicted the drop in AHI in response to placebo CPAP. Highly distressed patients showed greater placebo response, with a 34% drop (i.e., improvement) in AHI. Conclusion. These findings underscore the importance of placebo-controlled studies of CPAP treatment. Whereas such trials are routinely included in drug trials, this paper argues for their importance even in mechanical-oriented sleep interventions.