Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Course of disability reduction during a pain rehabilitation program: a prospective clinical study Franka P.C. Waterschoot a , Pieter U. Dijkstra a,b , Jan H.B. Geertzen a and Michiel F. Reneman a The aim of this study was to analyze the course of reduction of disability during a pain rehabilitation program (PRP) and factors influencing this course. A prospective cohort study was carried out. All patients with chronic musculoskeletal pain treated in a PRP between March 2010 and December 2010 were eligible for this study. All patients were treated at a University-based rehabilitation center and received an outpatient multidisciplinary PRP. Main outcome measures, Pain Disability Index (PDI), and average pain measured with a numeric rating scale were measured every 2 weeks during the PRP. To analyze the course of disability, a linear mixed- effect model was applied. One hundred and twenty-eight patients participated in the study, of whom 20% dropped out during the PRP. Initial PDI (β = 0.8), treatment week (β = - 0.2), treatment week squared (β = 0.03), average pain (β = 2.3), and interaction between initial PDI and treatment week (β = - 0.02) influenced the course of disability during PRP. Disability reduces during the PRP. Initial PDI, treatment week, average pain, and interaction between initial PDI and treatment week influence the course of disability reduction during the PRP. These results could aid in predicting the required duration of a PRP at the start. International Journal of Rehabilitation Research 00:000–000 © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. International Journal of Rehabilitation Research 2014, 00:000–000 Keywords: chronic pain, disability, Pain Disability Index, patient care team, rehabilitation a Department of Rehabilitation Medicine, Centre for Rehabilitation and b Department of Oral and Maxillofacial Surgery, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands Correspondence to Franka P.C. Waterschoot, BSH, Department of Rehabilitation Medicine, Center for Rehabilitation, University Medical Center Groningen, University of Groningen, PO Box 30002, 9750 RA Haren, Groningen, The Netherlands Tel: + 31 505 338 444; fax: + 31 505 338 570; e-mail: f.p.c.waterschoot@umcg.nl Received 21 February 2014 Accepted 26 August 2014 Introduction On the basis of pre and post measurements, it is known that pain rehabilitation programs (PRPs) are effective in disability reduction in patients with chronic musculoske- letal pain (CMP) (Guzman et al., 2001; Jensen et al., 2001; McCracken and Turk, 2002; Skouen et al., 2002; Gatchel and Okifuji, 2006; Smeets et al., 2006; Scascighini et al., 2008). However, the course of disability reduction is unknown. Understanding the course of disability reduc- tion could aid in determining the optimum duration of PRPs. This understanding would benefit patients, clin- icians, insurance companies, and healthcare providers because it prevents overtreatment or undertreatment and contributes toward better use of (public) recourses. A wide diversity of content, composition, and duration of PRPs exist (Guzman et al., 2001; Scascighini et al., 2008). In one systematic review, differences in duration were unrelated to differences in outcomes (Scascighini et al., 2008). However, in another review it was reported that multidisciplinary PRP of more than 100 h was superior to monodisciplinary treatment, and that multidisciplinary PRP of less than 30 h was not superior to mono- disciplinary treatment. Although the authors focused on the content of different PRPs and the review was designed to assess the effect of PRP, they concluded that PRPs of more than 100 h were more effective. The conclusions of these reviews were used to establish guidelines and clinical practice (Airaksinen et al., 2006; Van Hooff et al., 2010). However, these conclusions were based only on pre–post assessments. To our knowledge, no studies have analyzed the course of disability reduc- tion during the programs to establish the optimum duration of a PRP. In addition, it is unknown whether the improvements gained with intensive PRPs are worth the expenses (Guzman et al., 2001). Theoretically, if 90% of the improvements are observed in the first half of the PRP, it may be debated whether these 100 h or more, as proposed by Guzman et al. (2001), are needed. Because no previous research is available into this spe- cific aspect of PRPs, we hypothesized that there would be several possible courses of reduction of disability (Fig. 1). Line A assumes that the course of disability has a steeper slope at the end of the PRP. This implies that disability decreases most in the last part of the PRP. In contrast, line B assumes a steeper slope at the first half of the PRP. This implies that disability decreases most in the first part of the PRP. Line C implies a linear decrease of disability, and an alternating pattern of decrease and increase during the PRP is hypothesized in line D. The aim of this study was to analyze the course of reduction of disability during PRP and to analyze factors influencing this course. Original article 1 0342-5282 © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/MRR.0000000000000087