Medication compliance to statin therapy and its impact on disease outcomes in type 2 diabetes

UnrestrictedObjective: To examine long-term patient compliance to statin therapy in type 2 diabetes and its impact on various disease outcomes.; Methods: The California Medicaid program (Medi-Cal) claims data collected during the period of January 1995 to December 2004 was analyzed. Medication compliance was measured using Proportion of Days Covered (PDC) in each quarter of the study period. Descriptive analyses were performed to: 1) understand the trend of statin therapy in type 2 diabetes; 2) examine patient compliance to statin therapy and its change over time; and 3) compare long-term medication compliance to statin and to antidiabetic agents. A marginal structural model was employed to examine the impact of medication compliance to statin therapy on cardiovascular events. The effects of compliance on hospitalization and total medical costs were estimated by generalized estimating equations (GEE).; Results: Statin therapy was initiated earlier in patients with type 2 diabetes. Patient compliance to statin therapy was high (PDC=0.83, SD=0.234) during the first quarter of statin treatment. However, patient compliance dropped sharply from the second quarter (PDC=0.63, SD=0.382) and the medication compliance at the end of the first year of the treatment was decreased to 0.56. Over the 30 quarters, patients were less likely to comply with statin therapy than with antidiabetic treatment (approximately 35% difference). Hispanic patients and patients with complicated medication regimens were more likely to exhibit poor compliance to statin therapy. Compliance to statin therapy was significantly associated with decreased cardiovascular risk events (hazard ratio = 0.24; p<0.01) and less hospitalization in patients with type 2 diabetes (p