Worldwide, incidence of stroke in infants and young children is reported to be from 3 to 13 cases per 100,000, with a recurrence rate of 6% to 40% (Giroud et al 1995; Strater 2002; Roach et al 2008). Annual stroke incidence in individuals aged 15 to 45 varies greatly, depending on how estimates are derived, but appears to range from 5.83 to 12.1 cases per 100,000 persons (Kristensen et al 1997; Marini et al 2001; Groppo et al 2012). In developed Western countries, up to 13% of first-ever ischemic strokes occur in people younger than 45 years of age (Bogousslavsky et al 1988; Bogousslavsky and Pierre 1992; Nedeltchev et al 2005; Rasura et al 2006), whereas this age group may account for 20% to 30% of first-time strokes in developing countries (Radhakrishnan et al 1986; Al Rajeh and Awada 2002). The incidence of ischemic stroke ranges from 4/100,000 to 47/100,000 in those 25 to 34 years of age, and from 9/100,000 to 93/100,000 in those 35 to 44 years of age in the European population (Truelsen et al 2006). In the United States, the ethnic composition of the population may produce differences in reported stroke incidence among young individuals; the Baltimore-Washington Cooperative Young Stroke Study reported an annual cerebral infarction incidence of 10.55 per 100,000 Caucasians and 21.7 per 100,000 African Americans (Kittner et al 1993).
For intracerebral hemorrhage, the rate for whites was 3 per 100,000 and for African Americans was 9 per 100,000 (subarachnoid hemorrhage 60% and intracerebral hemorrhage 40%). The population-based Northern Manhattan Stroke Project study found incidence rates for stroke in the young of 23 per 100,000 persons (10 for infarct, 7 for intracerebral hemorrhage, and 6 for subarachnoid hemorrhage). The risk was more than 2-fold higher for blacks and Hispanics as compared with whites (Jacobs et al 2002). These urban and suburban North American population studies, however, found incidences somewhat higher than other studies. To put this entity into perspective, stroke in this age group is reportedly twice as prevalent as multiple sclerosis in 18- to 44-year-old persons (Collins 1997). Although the overall male: female ratio is equal between the ages of 15 and 45 years, females predominate if the age is restricted to below 30 years (Rasura et al 2006; Spengos and Vemmos 2010). This correlates with childbearing years when the risk is predominantly for hemorrhagic stroke. Based on a retrospective cohort of 336 patients aged 16 to 49 years (median age of 42) with a first-ever nontraumatic intracerebral hemorrhage, an annual incidence in the young was estimated at 4.9 per 100.00, with higher rates in males (6.2) than in females (4.0) (Koivunen et al 2015).