Prevalence and associated factors of premature discontinuation of antiplatelet therapy after ischemic stroke: a nationwide population-based study

BACKGROUND We tried to evaluate the prevalence of premature discontinuation of antiplatelets and its affecting factors after ischemic stroke using large-sized representative national claims data. METHODS Patients aged 20 years or older with newly confirmed ischemic stroke who started aspirin or clopidogrel for the first time were selected from 2003 to 2010 National Health Insurance Service-National Sample Cohort (NHIS-NSC) of South Korea (n = 4621), a randomly collected sample which accounts for 2.2% (n = 1,017,468) of total population (n = 46,605,433). The prevalence of discontinuation of antiplatelets was measured every 6 months until the 24 months since the first prescription. Then we classified the participants into 2 groups according to the discontinuation status at 12 months and assessed the factors influencing premature discontinuation of antiplatelets within 12 months. RESULTS Among total participants, 35.5% (n = 1640) discontinued antiplatelets within 12 months and 58.5% (n = 2704) discontinued them within 24 months. The remaining 41.5% (n = 1917) continued them for 24 months or more. In the multivariate logistic regression analysis, initiating treatment with aspirin monotherapy [adjusted OR (aOR), 2.66, 95% CI 2.17-3.25] was the most prominent determinant of premature discontinuation within 12 months followed by CCI score ≥ 6 (aOR 1.50, 95% CI 1.31-1.98), and beginning treatment with clopidogrel monotherapy (aOR 1.41, 95% CI 1.15-1.72). Rural residency (aOR 1.36, 95% CI 1.14-1.62), < 4 total prescribed drugs (aOR 1.24, 95% CI 1.05-1.47), lower income (aOR 1.20, 95% CI 1.03-1.40 for middle income class and OR 1.21, 95% CI 1.02-1.45 for low income class), and ages ≥70 years (aOR 1.15, 95% CI 1.00-1.31) were also significantly associated with premature discontinuation of antiplatelets within 12 months. CONCLUSIONS The prevalence of premature discontinuation of antiplatelets after ischemic stroke was quite high. Thus, by understanding factors associated with premature discontinuation, a more strategic approach is required for the physicians to improve persistence with antiplatelets.