Secular Trends in Ischemic Stroke Subtypes and Stroke Risk Factors

Abstract

Ischemic strokes account for ≈87% of all types of strokes; the distribution of ischemic stroke subtypes varies in different parts of the world.1 In Asia and South America, small vessel disease is the most prominent ischemic stroke subtype, whereas in Europe and the United States there is regional and ethnic variation in the distribution of stroke subtypes and their risk factors.2 Correctly identifying the cause of stroke is important for selection of the appropriate therapy to best reduce the risk of recurrence. 3 This may be particularly important in patients with minor or moderate stroke/transient ischemic attack (TIA), because they are less disabled, so will have more to lose from a recurrent stroke. With changing patterns of practice, in particular, increasing use of statins in the past decade, the distribution of risk factors and stroke subtypes in this population is expected to change over time. Changes in stroke subtypes resulting from these changes in practice can be expected to lead to changes in how physicians view the likelihood of different causes of stroke among their patients and plan strategies for investigation of their patients.The motivation for this study was the clinical suspicion, on the part of 2 senior stroke neurologists at our center, that cardioembolic strokes seemed to be increasing as a proportion of new patients referred to our local urgent TIA clinic. Our primary objective was to determine secular trends in ischemic stroke subtypes. We hypothesized that with more intensive management of atherosclerotic risk factors, there will have been a decrease in atherosclerotic risk factors and a decrease in large artery atherosclerosis and small vessel disease, and, in consequence, a proportional increase in cardioembolic stroke/TIA. Methods Study Setting and TimelineThis was a retrospective cohort study of patients diagnosed with minor or moderate stroke/TIA at the urgent TIA Clinic at University Hospital, a designated regional stroke hospital in London, Ontario. Based on Census reports from Statistics Canada, 599 538 residents were living in the referral area in 2006, and 619 881 residents were recorded in 2011. According to the 2011 census, 82% of the population of London are white, 2.7% Latin American, 2.6% Arab, 2.4% black, 2.2% South Asian, 2.0% Chinese, 1.9% Aboriginal, 1% Southeast Asian, 0.8% West Asian, 0.8% Korean, 0.6% Filipino, and 0.7% belong to other groups. In the surrounding farming area a higher Background and Purpose-Early diagnosis and treatment of a stroke improves patient outcomes, and knowledge of the cause of the initial event is crucial to identification of the appropriate therapy to maximally reduce risk of recurrence. Assumptions based on historical frequency of ischemic subtypes may need revision if stroke subtypes are changing as a result of recent changes in therapy, such as increased use of statins. Methods-We analyzed secular trends in stroke risk factors and ischemic stroke subtypes among patients with transient ischemic attack or minor or moderate stroke refer...

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