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Epidemiology and etiology of ischemic stroke in young adults aged 18 to 44 years in northern Sweden.

BACKGROUND AND PURPOSE
The aim of this study was to conduct a population-based epidemiological survey among young adults aged 18 to 44 years in Northern Sweden and furthermore to gain further insight into the etiology of ischemic stroke in this age group.


METHODS
Two studies were done. In the first part, epidemiological data were collected to calculate incidence and mortality from 1991 through 1994. This was based on the World Health Organization Northern Sweden MONICA register of acute stroke events. Eighty-eight first-ever ischemic stroke patients were identified during that period. In the second part, 107 consecutive patients aged 18 to 44 years with ischemic stroke referred to a university hospital were studied prospectively during a 5-year period and were extensively evaluated according to a standardized protocol. On the basis of modified Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria, the patients were classified into eight subtypes of ischemic stroke.


RESULTS
The average population-based annual incidence rate for ischemic stroke (cases per 100,000 per year) was 11.3 (95% confidence interval, 6.7 to 16.1). The case-fatality rate was 5.7%. According to the modified TOAST criteria, a probable cause of ischemic stroke was identified in 36% and remained unexplained in 21% of cases. Spontaneous cervical arterial dissection was the leading probable etiology (13%). Patent foramen ovale or atrial septal aneurysm was a possible cause of stroke in 28% of cases. The percentages of ischemic stroke attributed to IgG anticardiolipin antibodies (4.7%), atherothrombotic vasculopathy (3.7%), oral contraceptive use (7%), and migraine (1%) were lower than reported in recent clinical series.


CONCLUSIONS
The incidence rate for ischemic stroke was higher than previously reported from most countries in Western Europe. The higher incidence was not explained by a higher prevalence of premature atherosclerotic vasculopathy. Without the additional diagnostic information derived from advanced cardiac imaging, the proportion of indeterminate cases would have constituted 37% of the patients.