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 (κ = 0.21). On multiple logistic regression analysis, increased age (p≤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≤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≤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.