Increase in Daily Steps During the Early Phase of a Physical Activity Intervention for Type 2 Diabetes as a Predictor of Intervention Outcome.

BACKGROUND This pilot study aimed to test whether increase in daily steps and day-to-day consistency in daily steps during the first several weeks of a physical activity intervention predicted outcomes. METHODS This was a secondary analysis from two concurrent studies testing a positive psychology-motivational interviewing intervention to increase physical activity and positive affect in individuals with type 2 diabetes. Steps were measured with accelerometers at study assessments (baseline, end-of-treatment, and 8-week follow-up) and were measured daily throughout the intervention by participants using provided pedometers. We calculated change in steps from intervention week 1 to week 3, along with variability in daily steps over the first 3 weeks, using the best fitting regression line modeling their change. Multiple regression analyses tested whether these predictors were associated with change in physical activity at the end of treatment and at 8-week follow-up. Additionally, we explored the utility of specific cutoffs (e.g., 500 steps) for early step change using a minimum p-value approach. RESULTS In 52 participants, larger step increases by week 3 predicted activity increase at end-of-treatment and follow-up. Variability in early steps was not associated with outcomes. Early increase cutoffs of 500 and 2000 steps may have practical relevance. CONCLUSION Early response to a physical activity intervention appears to be a useful predictor of outcome and could be used to identify those unlikely to succeed in a given intervention early in treatment. TRIAL REGISTRATION ClinicalTrials.gov identifiers NCT03150199 and NCT03001999.