Long-term trends in incidence and risk factors for ischaemic stroke subtypes: Prospective population study of the South London Stroke Register

Background
As the average life expectancy increases, more people are predicted to have strokes. Recent studies have shown an increasing incidence in certain types of cerebral infarction. We aimed to estimate time trends in incidence, prior risk factors, and use of preventive treatments for ischaemic stroke (IS) aetiological subtypes and to ascertain any demographic disparities.
Methods and findings
Population-based data from the South London Stroke Register (SLSR) between 2000 and 2015 were studied. IS was classified, based on the underlying mechanism, into large-artery atherosclerosis (LAA), cardio-embolism (CE), small-vessel occlusion (SVO), other determined aetiologies (OTH), and undetermined aetiologies (UND). After calculation of age-, sex-, and ethnicity-specific incidence rates by subtype for the 16-year period, we analysed trends using Cochran-Armitage tests, Poisson regression models, and locally estimated scatterplot smoothers (loess). A total of 3,088 patients with first IS were registered. Between 2000–2003 and 2012–2015, the age-adjusted incidence of IS decreased by 43% from 137.3 to 78.4/100,000/year (incidence rate ratio [IRR] 0.57, 95% CI 0.5–0.64). Significant declines were observed in all subtypes, particularly in SVO (37.4–18; p < 0.0001) and less in CE (39.3–25; p < 0.0001). Reductions were recorded in males and females, younger (<55 years old) and older (≥55 years old) individuals, and white and black ethnic groups, though not significantly in the latter (144.6–116.2; p = 0.31 for IS). A 4-fold increase in prior-to-stroke use of statins was found (adjusted odds ratio [OR] 4.39, 95% CI 3.29–5.86), and despite the increasing prevalence of hypertension (OR 1.54, 95% CI 1.21–1.96) and atrial fibrillation (OR 1.7, 95% CI 1.22–2.36), preventive use of antihypertensive and antiplatelet drugs was declining. A smaller number of participants in certain subgroup-specific analyses (e.g., black ethnicity and LAA subtype) could have limited the power to identify significant trends.
Conclusions
The incidence of ISs has been declining since 2000 in all age groups but to a lesser extent in the black population. The reported changes in medication use are unlikely to fully explain the reduction in stroke incidence; however, innovative prevention strategies and better management of risk factors may contribute further reduction.

背景 随着人均预期寿命持续提升，预计脑卒中患者数量将不断增加。近期研究显示，部分类型脑梗死的发病率呈上升态势。本研究旨在估算缺血性脑卒中（ischaemic stroke, IS）各病因亚型的发病率、既往危险因素及预防性治疗的时间变化趋势，并明确相关人口统计学差异。

方法与结果 本研究分析了2000年至2015年南伦敦脑卒中登记库（South London Stroke Register, SLSR）的人群数据。依据发病机制，将缺血性脑卒中分为大动脉粥样硬化型（large-artery atherosclerosis, LAA）、心源性栓塞型（cardio-embolism, CE）、小血管闭塞型（small-vessel occlusion, SVO）、其他明确病因型（other determined aetiologies, OTH）及病因未明确型（undetermined aetiologies, UND）。在计算16年间各亚型按年龄、性别及种族划分的特异性发病率后，采用科克兰-阿米蒂奇趋势检验、泊松回归模型及局部加权散点平滑（locally estimated scatterplot smoothers, LOESS）进行趋势分析。本研究共登记3088例首发缺血性脑卒中患者。2000-2003年至2012-2015年期间，缺血性脑卒中的年龄标化发病率下降了43%，从137.3/10万人·年降至78.4/10万人·年（发病率比[IRR] 0.57，95%置信区间[CI] 0.5~0.64）。所有亚型的发病率均出现显著下降，其中小血管闭塞型（SVO）下降尤为显著（从37.4降至18；p<0.0001），心源性栓塞型（CE）下降幅度相对较小（从39.3降至25；p<0.0001）。男女各年龄组（<55岁及≥55岁）以及白人与黑人种族群体的发病率均有所下降，但黑人群体的下降未达到统计学显著性（缺血性脑卒中发病率从144.6降至116.2；p=0.31）。卒中前他汀类药物的使用量增长了4倍（校正比值比[OR] 4.39，95%CI 3.29~5.86）；尽管高血压（校正OR 1.54，95%CI 1.21~1.96）与心房颤动（校正OR 1.7，95%CI 1.22~2.36）的患病率呈上升趋势，但降压药物与抗血小板药物的预防性使用却呈下降态势。部分亚组分析的样本量较小（如黑人种族及大动脉粥样硬化型亚型），可能限制了其检出显著性趋势的统计效能。

结论 2000年以来，各年龄组的缺血性脑卒中发病率均呈下降趋势，但黑人人群的下降幅度相对较小。本研究中报道的药物使用变化难以完全解释脑卒中发病率的下降；不过，创新的预防策略及更优化的危险因素管理或可进一步降低脑卒中的发病率。