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Risk of ischemic stroke varies by ethnicity in patients with atrial fibrillation: A Swedish national cohort study

Published:September 01, 2016DOI:https://doi.org/10.1016/j.ejim.2016.08.027
      AF is an established independent risk factor for ischemic stroke as shown by many previous studies [
      • Wolf P.A.
      • Abbott R.D.
      • Kannel W.B.
      Atrial fibrillation as an independent risk factor for stroke: the Framingham study.
      ]. Anticoagulants are highly effective in reducing the risk of subsequent stroke in AF patients [
      • Spinler S.A.
      • Shafir V.
      New oral anticoagulants for atrial fibrillation.
      ]. They have been recommended by the American Heart Association to prevent ischemic stroke [
      • January C.T.
      • Wann L.S.
      • Alpert, J.S.
      • Calkins H.
      • Cigarroa J.E.
      • Cleveland Jr., J.C.
      • et al.
      2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society.
      ]. Some AF patients will develop ischemic stroke although they are treated with anticoagulants [
      • Ansari J.G.
      • Garcha G.S.
      • Lakkis N.
      Oral anticoagulation in atrial fibrillation.
      ]. It is thus important to identify risk factors that are associated with an increased risk of stroke in AF patients. The incidence of stroke was found to be somewhat higher among AF patients in Asian countries as compared to patients from the USA and European countries [
      • Mathur R.
      • Pollara E.
      • Hull S.
      • Schofield P.
      • Ashworth M.
      • Robson J.
      Ethnicity and stroke risk in patients with atrial fibrillation.
      ]. However, the different welfare systems as well as the various guidelines for the management of AF patients in different countries preclude a concrete conclusion whether there are ethnic differences in the risk of stroke in AF patients. In this study, we will explore whether immigrants with AF have a different risk of stroke as compared to native Swedes. (See Table 1.)
      Table 1Adjusted hazard ratio for associations between sociodemographic characteristics and subsequent stroke.
      No. of individuals Person-years of follow-up No. of strokes Rate per 100 person-years Model 1 Model 2
      HR 95% CI HR 95% CI
      Birth country or region
      Sweden 126,897 356,940 8079 2.3 Reference Reference
      Scandinavia 7387 21,102 486 2.3 1.1 1.0 1.2 1.0 1.0 1.2
      Western Europe 1861 5122 115 2.2 0.9 0.8 1.1 1.0 0.8 1.2
      East Europe and Soviet 3894 10,937 251 2.3 1.1 1.0 1.3 1.1 1.0 1.3
      Mediterranean 404 1100 26 2.4 1.3 0.9 2.0 1.3 0.9 1.9
      Turkey and Middle East 1562 4574 86 1.9 1.3 1.0 1.6 1.3 1.0 1.6
      India, Pakistan, Afghanistan 130 362 7 1.9 1.3 0.6 2.9 1.3 0.6 3.0
      East and Southeast Asia 169 475 8 1.7 1.0 0.5 2.2 1.0 0.5 2.1
      Chile 128 386 14 3.6 2.0 1.1 3.5 1.9 1.1 3.4
      Others 737 2152 29 1.3 0.8 0.5 1.2 0.8 0.6 1.2
      Age at diagnosis (years)
      <60 23,691 78,191 535 0.7 Reference Reference
      60–69 35,344 106,834 1471 1.4 1.9 1.7 2.1 1.8 1.6 2.0
      70–79 43,094 123,757 2848 2.3 3.1 2.8 3.4 2.8 2.6 3.1
      80+ 41,040 94,372 4247 4.5 5.5 5.0 6.0 5.0 4.5 5.5
      Gender
      Male 80,033 229,045 4165 1.8 Reference Reference
      Female 63,136 174,110 4936 2.8 1.2 1.1 1.2 1.2 1.1 1.2
      Education (years)
      9 60,372 165,115 4711 2.9 Reference
      10–11 36,879 104,207 2169 2.1 0.9 0.9 1.0
      12+ 45,918 133,833 2221 1.7 0.9 0.8 0.9
      Diabetes
      No 132,280 372,608 8216 2.2 Reference
      Yes 10,889 30,547 885 2.9 1.3 1.2 1.4
      Obesity
      No 141,283 398,058 8976 2.3 Reference
      Yes 1886 5097 125 2.5 1.1 0.9 1.3
      Alcoholism
      No 139,534 393,135 8852 2.3 Reference
      Yes 3635 10,020 249 2.5 1.1 0.9 1.2
      Hypertension
      No 5224 15,612 106 0.7 Reference
      Yes 137,945 387,543 8995 2.3 1.9 1.6 2.3
      All 143,169 403,155 9101 2.3
      Bold type shows that 95% confidence intervals do not overlap with 1.00.
      HR, hazard ratio; CI, confidence interval.

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