Risk factors associated with antihypertensive medication nonadherence in a statewide Medicaid population.

Background: This study seeks to determine the most important patient factors and health care exposures available through administrative databases associated with antihypertensive nonadherence.

Methods: This is a cross-sectional analysis of Medicaid hypertensive patients of Tennessee enrolled for 3 to 7 years from 1994 to 2000. Demographic characteristics, comorbidity and health care utilization were assessed during a 2-year period. The primary outcome was antihypertensive medication refill nonadherence. Subjects were categorized as adherent or nonadherent using an 80% cutoff criteria. Associations with nonadherence were assessed using logistic regression modeling.

Results: Of 49,479 subjects, 60.6% (n = 29,970) were classified as nonadherent and 39.4% (n = 19,509) as adherent. Significant predictors of nonadherence in multivariate analysis (P < 0.05) included male sex (odds ratio [OR] 1.12), black race (OR 1.67), urban residence (OR 1.12), obesity (OR 1.10), mental illness (OR 1.08) and substance abuse (OR 1.43). Significant protective factors included age (OR 0.97), disability (OR 0.62), diabetes (OR 0.76), hypercholesterolemia (OR 0.72) and Charlson index (OR 0.97). When health care utilization was considered, increased outpatient visits were associated with decreased nonadherence. Emergency department visits (OR 1.07) and hospital visits (OR 1.12) were associated with increased nonadherence.

Conclusions: This cross-sectional study suggests that substance abuse, black race, emergency department visits and hospitalizations are risk factors associated with nonadherence. Outpatient visits are associated with a small decrease in nonadherence. Further studies are needed to determine the characteristics of outpatient visits that most improve adherence.