Impact of Adherence and Weight Loss on Glycemic Control in Patients with Type 2 Diabetes: Cohort Analyses of Integrated Medical Record, Pharmacy Claims, and Patient-Reported Data

BACKGROUND: Managed care organizations put great effort into managing the population of patients with type 2 diabetes mellitus (T2DM) because of the health and economic burden of this disease. In patients with T2DM, weight loss and glycemic control are primary treatment aims to help improve patient outcomes, but these goals are not easily achieved. While achieving these aims requires a multifaceted approach of drug therapy management and lifestyle modification, truly understanding the role of medication adherence in achieving these outcomes is important for both patient and population management. This study expands on existing evidence that weight loss is associated with improved glycemic control by examining the role of medication adherence in achieving these goals in a managed care setting. This study is unique in that these associations are evaluated using multiple sources of data, including medical records for treatment outcomes, pharmacy claims, and patient-reported data to assess medication adherence. These data sources represent those typically available to payers or providers. OBJECTIVES: To describe the relationships between medication and adherence, weight change, and glycemic control in patients with T2DM. METHODS: This historical cohort study included adult patients with T2DM in a large integrated health system and was based on electronic health record and pharmacy claims data from November 1, 2010, through October 31, 2011, as well as data from a self-reported adherence survey conducted in March 2012. Included patients received a diabetes medication from a therapeutic class not previously received, between November 1, 2010, and April 30, 2011 (index date), who had blood glucose (HbA1c) and weight values at index date and 6 months follow-up, participated in an adherence survey, and had ≥ 1 prescription claim for the index-date drug. Associations between the dual outcomes of weight loss (≥ 3%) and HbA1c control ( less than 7.0%), while controlling for medication adherence and other demographic, treatment, and clinical variables, were evaluated using structural equation models (SEM). Separate models adjusted for different measures of medication adherence—self-reported using the 5-item Medication Adherence Rating Scale (MARS-5) and a modified medication possession ratio (mMPR) from pharmacy claims data. RESULTS: The study included 166 patients with a mean age of 61.1 (standard deviation = 12.1) years; 56.0% were female. Medication adherence was high, with 72.2% adherent using MARS-5 and 77.1% using mMPR measures. The SEMs found that only self-reported medication adherence is associated with weight loss (MARS-5: OR = 1.70, 95% CI = 1.11-2.60), while both self-reported and claims-based medication adherence were associated with HbA1c less than 7.0% (MARS-5: OR = 1.59, 95% CI = 1.09-2.34; mMPR: OR 2.71, 95% CI = 1.22-5.98). Further, weight loss is significantly associated with HbA1c less than 7.0% (MARS-5: OR = 3.60, 95% CI = 2.39-5.46; mMPR: OR 2.99, 95% CI = 1.45-6.17). CONCLUSIONS: This study has provided additional evidence in a managed, integrated setting that in patients treated for T2DM, weight loss is associated with good glycemic control. Adherence is associated with weight loss according to self-report, but not claims-based adherence measures. Adherence is also associated with glycemic control as measured by the 2 different methods. This study adds to the body of literature highlighting the importance of adherence as well as weight loss in achieving good glycemic control. The fact that the association of weight loss and adherence on glycemic control outcomes was significant regardless of medication adherence method is important in payer-provider collaborations, where access to data sources to evaluate adherence may vary. This study also supports continued investment in weight loss and adherence programs in the management of patients with T2DM.