ObjectiveTo investigate incidence of stroke and its subtypes in young adults, according to sex and age, and to study trends over time.MethodsWe established a nationwide cohort through linkage of national registries (hospital discharge, cause of death, and population register) with patients aged 18–50 years and those ≥50 years with first-ever ischemic stroke, intracerebral hemorrhage, or unspecified stroke, using ICD-9/ICD-10 codes between 1998 and 2010 in the Netherlands. Outcomes were yearly incidence of stroke stratified by age, sex, and stroke subtype, its changes over time, and comparison of incidence in patients 18–50 years to patients ≥50 years.ResultsWe identified 15,257 patients (53% women; mean age 41.8 years). Incidence increased exponentially with age (R² = 0.99) and was higher for women than men, most prominently in the youngest patients (18–44 years). The relative proportion of ischemic stroke increased with age (18–24 years: 38.3%; 44–49 years: 56.5%), whereas the relative proportion of intracerebral hemorrhage decreased (18–24 years: 34.0%; 44–49 years: 18.3%). Incidence of any stroke in young adults increased (1998: 14.0/100,000 person-years: 2010: 17.2; +23%; p < 0.001), driven by an increase in those aged over 35 years and ischemic stroke incidence (46%), whereas incidence decreased in those ≥50 years (329.1%–292.2%; −11%; p = 0.009).ConclusionsIncidence of any stroke in the young increases with age in patients over 35, is higher in women than men aged 18–44 years, and has increased by 23% in one decade, through an increase in ischemic stroke. Incidence of intracerebral hemorrhage is comparable for women and men and remained stable over time.