Can we identify how programmes aimed at promoting self-management in musculoskeletal pain work and who benefits? A systematic review of sub-group analysis within RCTs

BACKGROUND: There are now several systematic reviews of RCTs testing self-management for those with chronic musculoskeletal pain. Evidence for the effectiveness of self-management interventions in chronic musculoskeletal pain is equivocal and it is not clear for which sub-groups of patients SM is optimally effective. AIMS: To systematically review randomized controlled trials of self-management for chronic musculoskeletal pain that reported predictors, i.e., 'baseline factors that predict outcome independent of any treatment effect'; moderators, i.e., 'baseline factors which predict benefit from a particular treatment'; or mediators i.e., 'factors measured during treatment that impact on outcome' of outcome. METHOD: We searched relevant electronic databases. We assessed the evidence according to the methodological strengths of the studies. We did meta-regression analyses for age and gender, as potential moderators. RESULTS: Although the methodological quality of primary trials was good, there were few relevant studies; most were compromised by lack of power for moderator and mediator analyses. We found strong evidence that self-efficacy and depression at baseline predict outcome and strong evidence that pain catastrophizing and physical activity can mediate outcome from self-management. There was insufficient data on moderators of treatment. CONCLUSIONS: The current evidence suggests four factors that relate to outcome as predictors/mediators, but there is no evidence for effect moderators. Future studies of mediation and moderation should be designed with 'a priori' hypotheses and adequate statistical power