Brief communication: use of the minimal important difference for a meta-analysis on exercise and anxiety in adults with arthritis.

A recent meta-analysis reported statistically significant improvements in anxiety as a result of exercise in adults with arthritis and other rheumatic diseases (AORD) using the traditional standardized mean difference (SMD) effect size (ES). The objective of this study was to use the more recently developed and clinically relevant minimal important difference (MID) approach to examine this association. Data from a previous meta-analysis of 14 randomized controlled trials representing 926 initially enrolled adults ≥ 18 years of age (539 exercise, 387 control) was used to calculate the ES using the MID approach. Minimal important difference data were derived from previously reported anchor-based values that represented the different instruments used to assess anxiety. Effect sizes were pooled using the inverse heterogeneity (IVhet) model. Overall, exercise resulted in a mean ES reduction in anxiety of - 0.80 (95% CI, - 1.60 to 0.001, p = 0.05; Q = 92.1, p < 0.001, I 2  = 83.7%, 95% CI, 74.9%, 89.5%), suggesting that overall, exercise may benefit an appreciable number of patients. Nonetheless, this effect spanned the range from many patients gaining important benefits to no patients improving. The clinically relevant effects of exercise on anxiety in adults with AORD are varied. However, these results should be interpreted with caution given the absence of anchor-based MID data specific to the instruments and questions used to assess anxiety in adults with AORD. A need exists for future research to establish instrument-specific, anchor-based MID values for questions assessing anxiety in adults with AORD.