Epidemiology of first and recurrent ischemic stroke in Sweden 2010-2019-A Riksstroke study

Introduction: Ischemic stroke (IS) incidence appears to have decreased during the last decades, but most studies focus on first-ever events and epidemiologic 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 IS between 2010 and 2019 in Sweden. Methods: We included patients (>= 18 years) with IS registered in the hospital-based Swedish Stroke Register (Riksstroke) 2010 to 2019. The coverage of Riksstroke was consistently high (about 90%) during this period. Data were stratified by first-ever and recurrent IS 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. Results: During the study period, 201,316 cases of IS were registered in Riksstroke, including 153,865 (76.4%) cases of first-ever IS and 46,248 (23.0%) cases of recurrent IS (0.6% of cases unclassified). The crude incidence of first-ever IS decreased by 17% from 216 (95% CI 214-218) to 179 (95% CI 177-181) between 2010-2012 and 2017-2019 whereas recurrent IS decreased by 33% from 72 (95% CI 71-73) to 48 (95% CI 47-49). Between these time periods, diminishing IS incidence was seen in all age groups with highest decline noted in those 75-84 years (928 (95% CI 914-943) to 698 (95% CI 686-709); -25% in first-ever IS and 361 (95% CI 351-370) to 219 (95% CI 213-226); -39% in recurrent IS) and >= 85 years (1674 (95% CI 1645-1703) to 1295 (95% CI 1270-1320); -23% in first-ever IS and 683 (95% CI 664-702) to 423 (95% CI 409-437); -38% in recurrent IS). Treatment with anticoagulants in patients with atrial fibrillation and lipid-lowering drugs increased considerably in patients with first-ever and recurrent IS both at admission and discharge during the study period. Conclusion: Whereas both first-ever and recurrent IS rates declined in Sweden between 2010 and 2019, the proportional decline was almost double for recurrent IS than for first-ever IS 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 IS are needed.