Abstract P281: Medication Adherence and Stroke/TIA Risk in Treated Hypertensives: Results from the REasons for Geographic and Racial Differences in Stroke (REGARDS) Study

Abstract

Background: Low medication adherence in treated hypertensives is an important modifiable barrier to achieving blood pressure (BP) control. The contribution of poor medication adherence to adverse cardiovascular outcomes such as stroke and transient ischemic attack (TIA) relative to other cerebrovascular risk factors is less well understood. We therefore examined the relationship between medication adherence and both adequate BP control (< 140/90 mmHg) and stroke/TIA incidence in treated hypertensive subjects (n = 15,071 subjects free of stroke/TIA at baseline; 51% black; 57% living in the Stroke Belt) in REGARDS, a population-based cohort study. Methods: BP was measured in the subject’s home by a trained health professional following a standardized protocol. Medication adherence was measured at baseline (4-item validated Morisky scale: 0 = perfect adherence, 4 = lowest adherence). Participants were contacted bi-annually by telephone for a median follow-up time of 5 years and self-reported stroke or TIA events were adjudicated by medical record review. We used logistic regression models to examine the association between medication adherence and BP control and Cox modeling to evaluate the effect of adherence on stroke/TIA risk, examining the mediating effects of systolic BP. Results: Perfect medication adherence (score = 0) was reported by 69% of subjects, 23% a score of 1, 5% a score of 2, and 3% a score of 3 or 4. Mean systolic BP varied from 130.8 ± 16.2 in those reporting perfect adherence (Morisky score of 0) to 137.8 ± 19.5 in those reporting low medication adherence (score of 3 or 4) (p for trend< 0.0001). Compared to a Morisky score of 0, each level of worsening medication adherence was associated with significant and increasing odds of inadequately controlled BP (≥ 140/90 mmHg) in fully adjusted models: score = 1, odds ratio (95% CI) = 1.19 (1.09 – 1.30); score = 2, 1.27 (1.08–1.49); score = 3 or 4, 2.21 (1.75 – 2.78). Compared to perfect adherence, low medication adherence was not independently associated with stroke [hazard ratio = 1.04 (95% CI: 0.51 – 2.12)] or stroke and/or TIA [hazard ratio = 0.81 (95% CI: 0.38 – 1.73)] after multivariable adjustment. However, in analyses with systolic BP as the mediating variable, low medication adherence was associated with an increased risk for stroke (hazard ratio = 1.08 (95% CI: 1.04 – 1.14) and for stroke and/or TIA [hazard ratio = 1.08 (95% CI: 1.03 – 1.12)] in fully adjusted models. Conclusion: These findings add further evidence that low medication adherence is strongly associated with poor BP control; and through BP, low adherence is also associated with an increased risk of stroke or TIA.