Adherence to Insulin Pen Therapy Is Associated with Reduction in Healthcare Costs Among Patients with Type 2 Diabetes Mellitus

BACKGROUND: Type 2 diabetes mellitus is a chronic metabolic disorder that poses a significant economic burden on the US healthcare system associated with direct and indirect medical costs, loss of productivity, and premature mortality. OBJECTIVES: To determine whether increased adherence to therapy among patients with type 2 diabetes who use an insulin pen is associated with reduced healthcare costs, and to describe the overall healthcare costs of patients with type 2 diabetes. METHODS: This retrospective claims database analysis used the Truven Health MarketScan Commercial and Medicare Supplemental databases to identify patients diagnosed with type 2 diabetes with at least 1 insulin pen prescription claim between January 2006 and September 2010. Insulin pen adherence was measured using the medication possession ratio (MPR). The cost outcomes included all-cause and type 2 diabetes-related costs by type of service (ie, inpatient, outpatient medical, outpatient pharmacy), which were calculated in 2011 US dollars. Insulin adherence and overall healthcare costs were evaluated over the 12-month postindex period. RESULTS: A total of 32,361 patients met the study inclusion criteria, with an average MPR of 0.63 (standard deviation [SD], 0.29). Overall, patients with type 2 diabetes who used an insulin pen had an average annual healthcare cost of $19,612, which was driven by inpatient costs (37.2%) and outpatient pharmacy costs (24.4%). There is a significant difference in the average annual per-patient healthcare expenditures between the least adherent group (MPR <0.20; 11.0% of patients) and the most adherent group (MPR >0.80; 34.6% of patients) $26,310 versus $23,839, respectively (P = .007). Patients with the greatest insulin adherence had higher overall pharmacy costs than patients with the lowest insulin adherence ($10,174 vs $5395, respectively; P <. 001). CONCLUSIONS: The total healthcare expenditures of patients with type 2 diabetes who utilized insulin pens decreased with improvement in adherence, suggesting that higher rates of medication adherence may present an opportunity to curb healthcare costs in insulin pen users. The average sample MPR for our study population was 0.63 (SD, 0.29), indicating that insulin adherence continues to be a challenge for successful diabetes management. More research is needed to better characterize the relationship between medication adherence and healthcare costs among insulin users with type 2 diabetes and to identify the key drivers of adherence among this patient group.