Methods: In parallel with a Cochrane review update, we requested individual participant data (IPD) from high quality randomized clinical trials of adults with our primary outcomes of interest, pain and functional limitations, and calculated global recovery. We compiled a master dataset including baseline participant characteristics, exercise and comparison characteristics, and outcomes at short-, moderate- and long-term follow-up. We conducted descriptive analyses, and one-stage IPD meta-analysis using multilevel mixed-effects regression of the overall treatment effect, and pre-specified potential treatment effect modifiers.
Results: We received IPD for 27 trials (3514 participants). For studies included in this analysis, compared to no treatment/usual care, on average exercise therapy reduced pain [mean effect/100 (95% CI): -10.7 (-14.1, -7.4)], a result compatible with a clinically important 20% smallest worthwhile effect. Exercise therapy reduced functional limitations with a clinically important 23% improvement [mean effect/100 (95% CI): -10.2 (-13.2, -7.3)] at the short-term follow-up. Not having heavy physical demands at work and medication use for low back pain were potential treatment effect modifiers–they were associated with superior exercise outcomes relative to non-exercise comparisons. Lower BMI was also associated with better outcomes in exercise compared to no treatment/usual care. This study was limited by inconsistent availability and measurement of participant characteristics.
Conclusions: This study provides potentially useful information to help treat patients and design future studies of exercise interventions that are better matched to specific subgroups.