Ischemic Stroke in the Young

Introduction

Age constitutes one of the most important nonmodifiable risk factors for cerebral infarction. About 15% of all the ischemic strokes occur in young adults. Since stroke predominately affects the elderly, most of the data gathered in pivotal clinical trials and population-based studies were obtained using cohorts of older patients with coexisting cardiac disease and atherosclerosis. In comparison to older individuals, however, patients aged 15–50 years have a lower prevalence of traditional vascular risk factors and a higher representation of uncommon causes of stroke; these differences necessitate a particularized, thoughtful approach and cause-specific treatments. This chapter hence focuses on the epidemiology, pathogenesis, and diagnostic investigations of ischemic stroke in the young.

Epidemiology of Stroke in the Young

The occurrence of stroke increases with age. In the Northern Manhattan Stroke (NOMAS) study, the reported annual incidence of stroke in individuals aged 20–44 years was 23 per 100,000 habitants . Of these, 45% were ischemic strokes, 30% intracerebral hemorrhages, and 26% subarachnoid hemorrhages. In comparison, in individuals older than 45 years, 80% of the strokes were ischemic, 15% intracerebral hemorrhages, and 5% subarachnoid hemorrhages. The stroke incidence also has racial and ethnic variations. In the NOMAS study, for example, the relative risk of stroke was 2.4 times higher in blacks and 2.5 times higher in Hispanics than in whites. Similarly, in the Greater Cincinnati/Northern Kentucky Stroke Study, the risk of first stroke in blacks relative to whites was 2.2 for subjects ≤34 years of age, 5.0 for 35–44 years, and 2.6 for 45–54 years .

Because stroke is a preventable condition, its incidence is influenced by the implementation of effective prevention programs. Analysis of temporal trends has shown a declining incidence of ischemic stroke in the elderly. In comparison, the rate of stroke in subjects aged 20–54 years has increased over time, particularly for the year 2005 compared to earlier time periods . Similarly, data from the US Nationwide Inpatient Sample show that the rate of stroke discharges for subjects of 15–44 years increased from 23% to 53% between 1995 and 2008 . These trends were accompanied by an increased prevalence of traditional vascular risk factors in young individuals, including arterial hypertension, diabetes mellitus, dyslipidemia, obesity, and smoking.

The prevalence of stroke in the general population increases exponentially with age. Data from the 2009–2012 National Health and Nutrition Examination Survey show that prevalence of stroke is about 0.2% for men and 0.5% for women aged 20–39 years; in comparison, the prevalence of stroke in men and women aged 60–79 years are 6.1% and 5.2%, respectively ( Table 106.1 ) . A substantial number of strokes are asymptomatic. This has raised the concern that the prevalence of stroke reported in observational studies and national surveys may underestimate the burden of cerebrovascular diseases in the general population. In the NOMAS study, for example, the prevalence of asymptomatic stroke in relatively young adults aged ≤65 years of age was 9.5% . Also, in a single-center retrospective study including young adults aged 18–50 years admitted with first-ever ischemic stroke, silent ischemic lesions were observed in about 28% of patients . Moreover, in the Helsinki Young Stroke Registry, 13% of the patients had radiological evidence of previous silent cerebral ischemia which was associated with type 1 diabetes mellitus, obesity, smoking, and increasing age .