Nationwide Trends in Incidence and Mortality of Stroke Among Younger and Older Adults in Denmark

To investigate the extent to which the incidence and mortality of a first-time stroke among younger and older adults changed from 2005 to 2018 in Denmark using nationwide registries. We used the Danish Stroke Registry and the Danish National Patient Registry to identify patients 18 to 49 years of age (younger adults) and those ≥50 years of age (older adults) with a first-time ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage. We computed age-standardized incidence rates and 30-day and 1-year mortality risks separately for younger and older adults and according to smaller age groups, stroke subtype, sex, and severity (Scandinavian Stroke Scale score). Average annual percentage changes (AAPCs) were computed to assess temporal trends. We identified 8,680 younger adults and 105,240 older adults with an ischemic stroke or intracerebral hemorrhage. The incidence rate per 100,000 person-years of ischemic stroke (20.8 in 2005 and 21.9 in 2018, AAPC -0.6 [95% confidence interval (CI) -1.5 to 0.3]) and intracerebral hemorrhage (2.2 in 2005 and 2.5 in 2018, AAPC 0.6 [95% CI -1.0 to 2.3]) remained steady in younger adults. In older adults, rates of ischemic stroke and intracerebral hemorrhage declined, particularly in those ≥70 years of age. Rates of subarachnoid hemorrhage declined, but more so in younger than older adults. Stroke mortality declined over time in both age groups, attributable largely to declines in the mortality after severe strokes. Most trends were similar for men and women. The incidence of ischemic stroke and intracerebral hemorrhage was steady in younger adults from 2005 to 2018, while it dropped in adults >70 years of age. Stroke mortality declined during this time.