Impact of Adherence to Antihypertensive Agents on Clinical Outcomes and Hospitalization Costs

Background: Cardiovascular diseases (CVD) represent a heavy economic burden on individuals, health services, and society. Low adherence to antihypertensive (AH) agents is acknowledged as a major contributor to the lack of blood pressure control, and may have a significant impact on clinical outcomes and healthcare costs. Objectives: To evaluate the impact of low adherence to AH agents on cardiovascular outcomes and hospitalization costs. Methods: A cohort of 59,647 patients with essential hypertension was reconstructed from the Regie de l'assurance maladie du Quebec and Med-Echo databases. Subjects included were between 45 and 85 years of age, without any evidence for symptomatic CVD, newly treated with AH agents between 1999 and 2002 and followed-up for a 3-year period. Adherence to AH agents was categorized as >= 0% or < 80%. The adjusted odds ratio (OR) for CVD events between the 2 adherence groups was estimated using a polytomous logistic analysis. A 2-part model was applied for hospitalization costs. Results: Patients with low adherence were more likely to have coronary disease (OR, 1.07; 95% confidence interval [CI], 1.00-1.13), cerebrovascular disease (OR, 1.13; 95% CI, 1.03-1.25), and chronic heart failure (OR, 1.42; 95% CI, 1.27-1.58) within the 3-year follow-up period. Among hospitalized patients, low adherence to AH therapy was associated with increased costs by approximately $ 3574 (95% CI, $2897-$4249) per person within a 3-year period. Conclusions: Low adherence to AH agents is correlated with a higher risk of vascular events, hospitalization, and greater healthcare costs. An increased level of adherence to AH agents should provide a better health status for individuals and a net economic gain.