Epidemiology of First and Recurrent Ischemic Stroke in Sweden 2010-2019: A Riksstroke Study

Ischemic stroke incidence appears to have decreased during the last decades, but most studies focus on the first-ever events and epidemiological data on recurrent stroke are scarce. The aim of our study was to investigate trends in incidence, risk factors, and medication in patients with first-ever and recurrent ischemic stroke between 2010 and 2019 in Sweden.

We included patients (≥18 years old) with ischemic stroke registered in the hospital-based Swedish Stroke Register (Riksstroke) 2010-2019. The coverage of Riksstroke was consistently high (about 90%) during this period. Data were stratified by first-ever and recurrent ischemic stroke in three different time periods (2010-2012, 2013-2016, and 2017-2019) and shown as crude and age-specific incidence rates per 100,000 person-years. Statistics Sweden provided census data on the Swedish population in different age groups.

During the study period, 201,316 cases of ischemic stroke were registered in Riksstroke, including 153,865 (76.4%) cases of first-ever ischemic stroke and 46,248 (23.0%) cases of recurrent ischemic stroke (0.6% of cases unclassified). The crude incidence of first-ever ischemic stroke decreased by 17% from 216 (95% CI 214-218) to 179 (95% CI 177-181) between 2010-2012 and 2017-2019, whereas recurrent ischemic stroke decreased by 33% from 72 (95% CI 71-73) to 48 (95% CI 47-49). Between these time periods, diminishing ischemic stroke incidence was seen in all age groups with highest decline noted in those aged 75-84 years (928 [95% CI 914-943] to 698 [95% CI 686-709]; -25% in first-ever ischemic stroke and 361 [95% CI 351-370] to 219 [95% CI 213-226]; -39% in recurrent ischemic stroke) and ≥85 years (1,674 [95% CI 1,645-1,703] to 1,295 [95% CI 1,270-1,320]; -23% in first-ever ischemic stroke and 683 [95% CI 664-702] to 423 [95% CI 409-437]; -38% in recurrent ischemic stroke). Treatment with anticoagulants in patients with atrial fibrillation and lipid-lowering drugs increased considerably in patients with first-ever and recurrent ischemic stroke both at admission and discharge during the study period.

Whereas both first-ever and recurrent ischemic stroke rates declined in Sweden between 2010 and 2019, the proportional decline was almost double for recurrent ischemic stroke than for first-ever ischemic stroke and most pronounced in the elderly. Increased use of secondary preventive drugs, in particular anticoagulants in atrial fibrillation, appears to have contributed, but further studies on precise causes for the decline in recurrent ischemic stroke are needed.