Participatory decision making, patient activation, medication adherence, and intermediate clinical outcomes in type 2 diabetes: a STARNet study.

PURPOSE Participatory decision making (PDM) is associated with improved diabetes control. We examine a causal model linking PDM to improved clinical outcomes that included patient activation and medication adherence. METHODS This observational study was conducted in 5 family physician offices. Diabetic patients were recruited by mail and by completing a study interest card at the conclusion of their office visit. Two survey questionnaires, administered 12 months apart, elicited patients' ratings of their physician's PDM style at baseline and their level of activation and medication adherence both at baseline and at follow-up. Measures of glycated hemoglobin (hemoglobin A(1c)), systolic blood pressure, and low-density lipoprotein (LDL) cholesterol were abstracted from the medical record starting 12 months before the baseline survey to 12 months after the follow-up survey. A path analysis using a structural equation model was used to test hypotheses. RESULTS We mailed questionnaires to 236 participants; 166 (70%) returned the baseline questionnaire, and 141 (80%) returned the follow-up questionnaire. Hemoglobin A(1c) levels, systolic blood pressure, and LDL cholesterol values all declined significantly, and patient activation and medication adherence improved. PDM at baseline was associated with patient activation at follow-up. Patient activation at follow-up was associated with medication adherence at follow-up, and medication adherence at follow-up was associated with change in hemoglobin A(1c) levels and LDL cholesterol values but not with systolic blood pressure. CONCLUSIONS Participatory decision making during primary care encounters by patients with type 2 diabetes resulted in improvements in hemoglobin A(1c) levels and LDL cholesterol values by improving patient activation, which in turn improved medication adherence.