The Michigan Stroke Transitions Trial (MISTT) is a pragmatic, un-blinded, 3-group randomized controlled trial conducted in 3 Michigan hospitals and designed to compare patient recovery under one of two interventions, (1) social worker case management (SWCM) and (2) social worker case management in addition to an online stroke recovery resource (VSSP), relative to usual care (UC). Using a difference-in-differences approach, and comparing outcome measures at 90-days post-discharge to outcomes at 7-days post-discharge, MISTT found significant positive outcomes in PROMIS physical health (p = 0.002) and Patient Activation (p = 0.06) in the VSSP treatment arm relative to UC. We hypothesized that emotional support and patient activation acted as sequential mediators in the pathway between randomly assigned treatment and physical and mental health. We estimated the direct and indirect effects of the interventions using an adapted version of the weighted approach. Multiple imputation was used to account for missing observations and bootstrapping was used to construct standard errors. We found no statistically significant (p < 0.05) mediation effects. That said, we observed a sizable positive natural direct effect of the VSSP treatment relative to usual care on patient physical health (+1.40, 95% CI: –0.56, 3.35). In addition, there appeared to be a negative partial natural indirect effect of the SWCM treatment on both mental and physical health which acted through patient activation, not emotional support. We report no mediated effects of statistical significance; however, some sizable effects bear further study. In particular, neither of our hypothesized mediators appeared to fully explain the positive effect of VSSP treatment on physical health shown in the MISTT primary results; and the lack of change in mental health found in MISTT might be explained by a decrease in patient activation found in the SWCM treatment arm.
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