Objective: To assess the impact of patient cost-sharing for antihypertensive medications on the proportion of days covered (PDC) by antihypertensive medications, medical utilization, and health care expenditures among commercially insured individuals assigned to different risk categories.
Methods: Participants were identified from the Consolidated Health Cost Guidelines (CHCG) database (January 1, 2006-December 31, 2008) based on a diagnosis (index) claim for hypertension, continuous enrollment ≥12 months pre- and post-index, and no prior claims for antihypertensive medications. Participants were assigned to: low-risk group (no comorbidities), high-risk group (1+ selected comorbidities), or very high-risk group (prior hospitalization for 1+ selected comorbidities). The relationship between patient cost sharing and PDC by antihypertensive medications was assessed using standard linear regression models, controlling for risk group membership, and various demographic and clinical factors. The relationship between PDC and health care service utilization was subsequently examined using negative binomial regression models.
Results: Of the 28,688 study patients, 66% were low risk. The multivariate regression model supported a relationship between patient cost sharing per 30-day fill and PDC in the following year. For every US$1.00 increase in cost sharing, PDC decreased by 1.1 days (P < 0.0001). Significant predictors of PDC included high risk, older age, gender, Charlson Comorbidity Index score, geography, and total post-index insurer- and patient-paid costs. An increase in PDC was associated with a decrease in all-cause and hypertension-related inpatient, outpatient, and emergency room visits and medical, pharmacy, and total costs.
Conclusions: The trend has been for managed care organizations and employers to require patients to bear a greater out-of-pocket burden for health care resources consumed. This study illustrates the potential adverse effects of higher patient cost sharing among patients with hypertension stratified by different risk levels. A decrease in PDC was predictive of higher resource utilization and health care costs, which should be of interest to payers and employers alike.
Keywords: adherence; cost sharing; hypertension; outcomes.