Adherence to medication in patients with heart failure : effect on mortality and hospitalization

Abstract

Heart failure is a chronic condition that increases the risk for death and disability. Beta blockers and ACE inhibitors have become standard treatments in heart failure because clinical trials have demonstrated their beneficial effect on mortality and morbidity in these patients. As not much is known about adherence to these medications, the main objectives of this project were to determine long term adherence to ACE inhibitors and beta blockers and determine how various degrees of adherence to a beta blocker can affect major health outcomes in patients with heart failure. Data was obtained from Saskatchewan health from January 1, 1994 to December 31, 2003 for all heart failure patients from their first hospitalization for heart failure. Adherence was calculated using the fill frequency measure of adherence, and all survival analyses were completed using the Cox proportional hazards model.Although 14, 000 patients were admitted to hospital for a first admission for heart failure, only 1143 subjects started a beta blocker and 5084 subjects started an ACE inhibitor within 3 months of the index hospitalization. Within the first year, adherence was excellent for both beta blockers (80.8 percent) and ACE inhibitors (82.5 percent). The proportion of patients remaining adherent slowly decreased to reach approximately 60 percent, for both medication classes, after 4 years. There was no significant difference in all-cause mortality between patients with high adherence and low adherence, but there appeared to be a trend towards decreased survival time in those remaining adherent throughout the study period [HR = 1.18 (95% CI: 0.98 to 1.43; p=0.07)].Since the overall rate of adherence to beta blockers was excellent in most patients during the first year, it is possible that non-adherence is not responsible for a significant burden of mortality in Saskatchewan heart failure patients, and perhaps and the focus of quality improvement should be optimal prescribing of evidence-based therapies, and continued adherence over time.