Hypertension treatment in a medicare population: Adherence and systolic blood pressure control

Background: Despite substantial trial evidence that demonstrates the effectiveness of pharmacologic treatment for reducing blood pressure (BP) and cardiovascular events, many patients are nonadherent to their hypertension treatment. Objectives: The purpose of this study was to examine patient adherence to hypertension medications using pharmacy data (ie, outpatient, inpatient, and mail-order prescriptions) and the association between adherence measures and systolic BP (SBP) control. Methods: The study included Medicare+Choice beneficiaries (aged >= 65 years) who were continuously enrolled in an integrated delivery system in 2003, and who had documented hypertension and received >= 1 hypertension drug in 2002. This analysis used automated clinical data and the 2000 US Census. We estimated 2 measures of hypertension treatment adherence in 2003 using the supply of dispensed drugs in days (proportion of days covered >= 80%): (1) adherence to >= 1 hypertension drug; and (2) adherence to the full hypertension treatment regimen. We defined the regimen by the number of hypertension drugs used concurrently in 2002. We assessed adherence annually and during the 30, 60, and 90 days before an SBP measurement. Logistic regression was used to examine the association between adherence and the number of drugs in the hypertension regimen, as well as the association between adherence and elevated SBP (>= 140 mm Hg). We adjusted for patient sociodemographic and clinical characteristics. Results: The majority (52.8%) of patients had multi-drug hypertension regimens. In 2003, 87.3% of subjects were adherent to >= 1 hypertension drug; 72.1% were adherent to their full regimen. After adjustment, we found that subjects with multidrug regimens were significantly more likely to be adherent to >= 1 drug and significantly less likely to be adherent to their full regimen, compared with patients on a 1-drug regimen. Over one-third of subjects had elevated SBP in 2003. Both adherence measures were associated with lower odds of having elevated SBP (eg, odds ratio = 0.87 [95% Cl, 0.84-0.89] for adherence to the full regimen). For subjects with multidrug regimens, partial adherence and nonadherence to the regimen were associated with higher odds of having elevated SBP. Conclusions: Adherence measures using automated pharmacy data can identify patients who are nonadherent to their drug treatment regimen and who are more likely to have inadequately controlled BP. Adherence measures that account for the number of drugs in a patients' drug regimen might help identify additional patients at risk for poor BP outcomes due to partial treatment adherence.