The Moderating Effects of Race and Ethnicity on a Motivational Interviewing Intervention for Improving Physical Health Among Patients With Peripheral Artery Disease: Secondary Analysis of a Pilot Randomized Trial.

BACKGROUND

In a pilot randomized trial, face-to-face or telephone motivational interviewing (MI) was more efficacious than a smartphone app after 3 months for increasing 6-minute walk distance (primary outcome) and reducing body weight (secondary outcome) in patients with peripheral artery disease (PAD). Little is known about intervention heterogeneity related to social determinants of health (SDOH).

OBJECTIVE

This study aimed to explore whether SDOH are associated with the MI intervention effects on walking distance and weight loss and generate intervention heterogeneity hypotheses.

METHODS

Community dwellers in Wichita, Kansas, were recruited through community outlets and screened for PAD. Consented participants were randomly assigned to MI (n=16) or an app (n=13). Survey instruments were used to measure SDOH, demographics, and adverse childhood experiences, which were assessed for their associations with 6-minute walk distance change and weight loss. Difference-in-differences (DiD) comparisons of median changes between SDOH strata were conducted using Wilcoxon and Kruskal-Wallis nonparametric tests.

RESULTS

For 6-minute walk distance, pretest-posttest changes were significantly greater among participants of "other" race and ethnicity than among non-Hispanic White participants (DiD=44.0 m, 95% CI 19.2-164.2; P=.004), and no DiDs for other SDOH were significant. Significant median pretest-posttest increases in walking distance were observed in those with a college or higher educational attainment (48.8 m, 95% CI 28.0-61.4), unmarried individuals (40.4 m, 95% CI 0.5-56.0), those living with family (55.7 m, 95% CI 30.5-199.5), those who talked to and saw family or friends 3 or more times a week (46.4 m, 95% CI 17.2-69.4), and those without unmet daily needs (46.5 m, 95% CI 7.6-67.1). For weight loss, we did not observe significant DiDs with any SDOH. However, a significant median weight loss was observed in every SDOH stratum where we observed a significant increase in 6-minute walk distance. Significant weight loss was also observed in 5 additional SDOH strata: male individuals, household income below US $30,000, never served in military, employed status, and no stress. The improvements in weight loss and walking distance were highly consistent in both direction and size across SDOH strata.

CONCLUSIONS

This pilot study was the first to explore potential SDOH-related intervention effect modification and heterogeneity. The significant association between walking distance and race and ethnicity suggested a potential effect modification. Significant pretest-posttest improvements in both outcomes were found in the same SDOH strata. The highly consistent evidence across both outcomes and all SDOH strata provided confidence in potential intervention efficacy and heterogeneity despite the small sample size. Our findings were consistent with established associations between SDOH and general functions in patients with PAD, suggesting likely mediation pathways through health literacy and social support. Future interventions should consider heterogeneity to target socially disadvantaged patients with PAD to bridge disparities and maximize benefits.

TRIAL REGISTRATION: ClinicalTrials.gov NCT03694652; https://clinicaltrials.gov/ct2/show/NCT03694652.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.2196/30295.