Association between higher rates of cardioprotective drug use and survival in patients on dialysis.

Abstract

While cardiovascular (CV) disease is a leading cause of morbidity and mortality in patients on chronic dialysis, utilization rates of cardioprotective drugs for dialysis patients remain low. This study sought to determine whether higher rates of cardioprotective drug use among dialysis patients might increase survival. A retrospective cohort of incident dialysis patients (n = 50,468) with dual eligibility for U.S. Medicare and Medicaid was constructed using USRDS data linked with billing claims. Medication exposures included angiotensin converting enzyme inhibitors/angiotensin receptor blockers (ACEIs/ARBs), β-blockers, calcium channel blockers (CCBs), and HMG-CoA reductase inhibitors (statins) prescribed within 90 days of dialysis initiation. The outcomes were one- and two-year survival and CV event-free survival. Variation in treatment rates based on local area practice styles were used as instruments in instrumental variable (IV) estimation, yielding average treatment effect estimates for patients whose treatment choices were affected by local area practice styles. Patients aged 65 years and older comprised 47.4% of the sample, while 59.5% were female and 35.0% were white. The utilization rate was 40.7% for ACEIs/ARBs, 43.0% for β-blockers, 50.7% for CCBs and 26.4% for statins. The local area practice style instruments were highly significantly related to cardioprotective drug use in dialysis patients (Chow-F values > 10). IV estimates showed only that higher rates of β-blockers increased one-year survival (β = 0.161, P-value = 0.020) and CV event-free survival (β = 0.189, P-value = 0.033), but that higher rates of CCBs decreased two-year CV event-free survival (β = -0.520, P-value = 0.009). This study suggests that higher utilization rates of β-blockers might yield higher survival rates for dialysis patients. However, higher rates of the other drugs studied had no correlations with survival, and higher CCB rates might actually reduce CV-event free survival. Since the benefits of cardioprotective drugs may vary across dialysis patients, the study findings should be interpreted only with respect to changes of utilization rates around the rates observed in this study.