Antihypertensive medication adherence, ambulatory visits, and risk of stroke and death

Abstract

Background: This study seeks to determine whether antihypertensive medication refill adherence, ambulatory visits, and type of antihypertensive medication exposures are associated with decreased stroke and death for community-dwelling hypertensive patients.

Methods: This retrospective cohort study included all chronic medication-treated hypertensives enrolled in Tennessee's Medicaid program (TennCare) for 3-7 years during the period 1994-2000 (n = 49,479). Health care utilization patterns were evaluated using administrative data linked to vital records during a 2-year run-in period and 1- to 5-year follow-up period. Antihypertensive medication refill adherence was calculated using pharmacy records.

Results: Associations with stroke and death were assessed using Cox proportional hazards modeling. Stroke occurred in 619 patients (1.25%) and death in 2,051 (4.15%). Baseline antihypertensive medication refill adherence was associated with decreased multivariate hazards of stroke [hazard ratio (HR) 0.91; 95% confidence interval (CI), 0.86-0.97 for 15% increase in adherence]. Adherence in the follow-up period was associated with decreased hazards of stroke (HR 0.92; CI 0.87-0.96) and death (HR 0.93; CI 0.90-0.96). Baseline ambulatory visits were associated with decreased death (HR 0.99; CI 0.98-1.00). Four major classes of antihypertensive agents were associated with mortality reduction. Only thiazide-type diuretic use was associated with decreased stroke (HR 0.89; CI 0.85-0.93).

Conclusions: Ambulatory visits and antihypertensive medication exposures are associated with reduced mortality. Increasing adherence by one pill per week for a once-a-day regimen reduces the hazard of stroke by 8-9% and death by 7%.

Figure 1

Adjusted Kaplan-Meier survival curves for stroke (panel A), death (panel B), and stroke or death (panel C) according to overall level of antihypertensive medication refill adherence.