Purpose: Patients with diabetes and comorbid cardiovascular disease (CVD) require polypharmacy to control both conditions and prevent complications. Few studies investigate the impact of multiple medication compliance on healthcare utilization. The study objective was to assess the relationship of multiple medication compliance with healthcare utilization.
Method: We identified patients ≥40 years of age with a diagnosis of type II diabetes and comorbid CVD including hypertension, coronary artery disease, and heart failure from California Medicaid claim data between 2002 and 2004. Proportion of days covered ≥0.8 was used to assess medication compliance. Finite mixture models (FMMs) with negative binomial density were used to estimate healthcare utilization in 2004 and its association with multiple medication compliance.
Result: A total of 21,740 patients were analyzed. Only 18% of patients were compliant with both diabetes and CVD medications, 32% compliant with only diabetes medication, 7% with only CVD medication, and 43% did not fill any appropriate medication or were non-compliant with any medication. FMMs classified patients to two latent classes (low- vs. high-users). Approximately 57% of patients were low-users and 43% were high-users for number of emergency room (ER) visits and prescription fills; while 80% were low-users vs. 20% high-users for number of hospitalizations and outpatient visits. High-users had 1.3 (prescription fills) to 4.0 (outpatient visits) times higher utilization than low-users. As compared to patients who did not fill or were non-compliant with both diabetes and CVD medications, those adherent to both diabetes and CVD medications in low-users class were significantly associated with increased 2.215±0.154 outpatient visits (p<0.001) and increased 15.470±0.835 prescription fills (p<0.001); but decreased 0.033±0.016 ER visits (p=0.04) and decreased 0.015±0.008 hospitalizations (p=0.09); while those adherent to both medications in high-users class were significantly associated with increased 21.005±2.151 outpatient visits (p<0.001) and increased 38.614±2.014 prescription fills (p<0.001), but decreased 0.050±0.024 ER visits (p=0.03) and decreased 0.081±0.030 hospitalizations (p=0.01).
Conclusion: Compliance with multiple medications had a significant impact on the increased utilization of outpatient visits and prescription fills, and the decreased utilization of ER visits and hospitalizations in a California Medicaid population with type II diabetes and comorbid CVD. Further study is needed to investigate whether an appropriate number of outpatient visits and prescription fills can help offset ER visits and hospitalizations.