Supplementary Material for: 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.

引言：近数十年来，缺血性脑卒中（Ischemic Stroke, IS）的发病率似乎有所下降，但多数研究仅聚焦于首次发作事件，关于复发脑卒中的流行病学数据仍较为匮乏。本研究旨在探讨2010至2019年间瑞典首次及复发缺血性脑卒中患者的发病率、危险因素与用药趋势。

方法：本研究纳入2010至2019年于基于医院的瑞典卒中登记库（Swedish Stroke Register, Riksstroke）中登记的18岁及以上缺血性脑卒中患者。此期间瑞典卒中登记库的登记覆盖率始终维持在较高水平（约90%）。研究按首次发作与复发缺血性脑卒中进行分层，并将数据分为三个时间段（2010–2012年、2013–2016年及2017–2019年），以每10万人年的粗发病率与年龄别发病率进行呈现。瑞典统计局提供了不同年龄组瑞典人口的普查数据。

结果：研究期间，瑞典卒中登记库共登记201316例缺血性脑卒中病例，其中153865例（76.4%）为首次发作缺血性脑卒中，46248例（23.0%）为复发缺血性脑卒中，另有0.6%的病例未分类。2010–2012年至2017–2019年间，首次发作缺血性脑卒中的粗发病率从216（95%置信区间：214–218）下降至179（95%置信区间：177–181），降幅达17%；复发缺血性脑卒中的粗发病率则从72（95%置信区间：71–73）下降至48（95%置信区间：47–49），降幅达33%。各年龄组的缺血性脑卒中发病率均呈下降趋势，其中75–84岁年龄组降幅最为显著：首次发作缺血性脑卒中从928（95%置信区间：914–943）降至698（95%置信区间：686–709），降幅25%；复发缺血性脑卒中从361（95%置信区间：351–370）降至219（95%置信区间：213–226），降幅39%。≥85岁年龄组同样可见明显下降：首次发作缺血性脑卒中从1674（95%置信区间：1645–1703）降至1295（95%置信区间：1270–1320），降幅23%；复发缺血性脑卒中从683（95%置信区间：664–702）降至423（95%置信区间：409–437），降幅38%。研究期间，首次及复发缺血性脑卒中患者在入院与出院时的心房颤动抗凝治疗与降脂药物使用比例均显著提升。

结论：2010至2019年间，瑞典首次与复发缺血性脑卒中的发病率均有所下降，但复发缺血性脑卒中的相对降幅几乎为首次发作的两倍，且该下降趋势在老年人群中最为显著。二级预防药物使用的增加，尤其是心房颤动患者的抗凝治疗，可能是该趋势的促成因素，但仍需进一步研究以明确复发缺血性脑卒中发病率下降的确切原因。