Abstract

Objective: For the MATCH intervention, assess concurrent validity of a single item Stage of Change (SOC) measure and association with effectiveness.

Methods: Observational pre, post intervention study in 17 schools in North and South Carolina. Subjects included 908 youth with all measures (908/1,468=62%) who participated in an interdisciplinary seventh grade wellness program called Motivating Adolescents with Technology to Choose Health (MATCH). Measures included: Pre and Post-MATCH self-reported SOC, frequency of fruit and vegetable intake (F/V) and Physical Activity (PA) and measured Body Mass Index z-score (zBMI). Concurrent validity was assessed using Wilcoxon rank tests (pre-action vs. action SOC category for F/V and PA at pre- and post-MATCH) and Spearman correlations (between change in SOC, F/V and PA). Change in SOC category distribution was assessed with McNemar’s test; association between change in SOC and change in zBMI was investigated with multiple regression.

Results: Both PA and F/V were found to be statistically significantly higher for students in the action SOC category (p<0.0001). Greater increase in SOC was weakly associated with a greater increase in PA (correlation 0.1069, p=0.0013). Participation demonstrated a shift in SOC post-MATCH (% in “action” SOC 47% pre, 53% post; p=0.003). ZBMI decreased significantly from pre- to post-MATCH (p<0.0001). A significant association existed between baseline SOC and change in zBMI: students with higher baseline SOC tended to have more decrease/less increase in zBMI (all overweight subgroup, b=-0.040, p=0.0108). Limitations: lack of a control group, survey questions not validated for individual behavior change.

Conclusion: The SOC measure appears to be valid. Participation in MATCH may improve SOC and baseline SOC may predict increased effectiveness; however this result must be considered cautiously in this observational study.