Abstract P341: Low Antihypertensive Medication Adherence is Associated with Increased Risk of Cardiovascular Events in Older Women and Men: Findings from the Cohort Study of Medication Adherence among Older Adults (CoSMO)
Background: Low adherence to antihypertensive medications is a major contributor to the lack of blood pressure control. However, few data are published on adherence to antihypertensive medications and clinical outcomes in older insured adults with established hypertension. We hypothesized that low medication adherence would be associated with increased risk of cardiovascular (CV) events.
Methods: Using longitudinal data from the Cohort Study of Medication Adherence in Older Adults (CoSMO), the risk of CV events associated with low pharmacy fill among 2,048 older adults treated for hypertension was assessed. The Medication Possession Ratio (MPR) for antihypertensive medications filled August 2005 to September 2006 (the year prior to the baseline survey) was calculated for each participant using fill data from administrative pharmacy databases. Low, medium, and high adherence were defined as an MPR <0.5, 0.5 to <0.8, and ≥0.8, respectively. CV events (stroke, myocardial infarction and chronic heart failure) were identified in administrative databases and adjudicated by clinicians following a structured protocol. Cox Proportional Hazards analysis was used to determine the risk of CV events associated with low or medium MPR.
Results: The mean age of participants was 75.0 ± 5.6 years, 60.1% (1,231 of 2,048) were female, 30.5% (625 of 2,048) were African-American, and 62.8% (1,287 of 2,048) had been diagnosed with hypertension for 10 or more years. The prevalence of low, medium and high MPR was 3.6% (74 of 2,048), 22.7% (466 of 2,048), and 73.6% (1,508 of 2,048), respectively. Of the 2048 participants, 217(10.6%) had a CV event over a median of 3.8 years of follow-up. Crude incidence rates for CV events by low, medium and high MPR were 17.6% (13 of 74), 12.9% (60 of 466), and 9.5% (144 of 1,508), respectively (P trend = 0.005). After multivariable adjustment for socio-demographics, comorbidities, classes of antihypertensive medication, and depressive symptoms and compared to those with high MPR, the hazard ratios (95% confidence interval) for CV events associated with medium and low MPR were 1.29 (0.95,1.76; P= 0.101) and 2.53 (1.41,4.54; P=0.002), respectively. The associations between low adherence and CV events were consistent across race and sex subgroups. The population attributable risk for CV events due to low or medium adherence was 9.4%.
Conclusion: Among older adults with hypertension, low adherence to antihypertensive medications was associated with increased risk of CV events. Interventions targeting older adults with low antihypertensive medication adherence may reduce risk of CV events.
- © 2013 by American Heart Association, Inc.