Factors Associated with Drug Adherence and Blood Pressure Control in Patients with Hypertension

STUDY OBJECTIVES: To determine characteristics associated with drug adherence and blood pressure control among patients with hypertension, and to assess agreement between self-reported and refill adherences. DESIGN: Cross-sectional analysis of baseline data from an ongoing randomized controlled trial. SETTING: Primary care center at an urban, county health system in Indianapolis, Indiana. PATIENTS: Four hundred ninety-two participants with hypertension and taking at least one antihypertensive drug. MEASUREMENTS AND MAIN RESULTS: Social and demographic factors, comorbidity, self-reported drug adherence, prescription refill adherence, and systolic and diastolic blood pressures were recorded at baseline. Participants were aged 57 +/- 11 (mean +/- SD) years, were predominantly women (73%) and African-American (68%), and took 2.4 +/- 1.1 antihypertensive drugs. Agreement between self-reported and refill adherences was poor to fair (kappa = 0.21). On multiple logistic regression analysis, increased age (p< or =0.002) and being married (p=0.03) were independent predictors of improved self-reported and refill adherence, whereas depressed patients had low self-reported adherence (p=0.005), and African-Americans had low refill adherence (p<0.001). Compared with nonadherent patients, adherent patients had lower systolic (-5.4 mm Hg by self-report and -5.0 mm Hg by refill) and diastolic (-2.7 mm Hg by self-report and -3.0 mm Hg by refill) blood pressures (p< or =0.02). Increased age was the only other variable strongly associated with systolic and diastolic blood pressure control in both measures of drug adherence (p< or =0.001). The association of depression, race, and sex with blood pressure control was model dependent. CONCLUSION: Age, sex, race and depression are associated with antihypertensive drug adherence and blood pressure control. Self-reported and refill adherences appear to provide complementary information and are associated with reductions in systolic and diastolic blood pressure of similar magnitude.