Supplementary Material for: Trends in One-Year Recurrent Ischemic Stroke among the Elderly in the USA: 1994–2002

<i>Background and Purpose:</i> Of the 795,000 strokes occurring in the USA each year, over 20% are recurrent events. Little is known about how the rates of recurrent stroke in the country have changed over time. Our objective was to determine national trends in 1-year recurrent ischemic stroke rates by US county among the elderly from 1994 to 2002. <i>Methods:</i> One-year recurrent stroke rates following incident ischemic stroke (ICD-9 433, 434, 436) among all fee-for-service Medicare beneficiaries were determined by US county for 1994–1996, 1997–1999, and 2000–2002. Bayesian spatiotemporal Poisson modeling was used to determine county-specific trends in recurrent stroke rates over time with risk adjustment for demographics, medical history and comorbid conditions. <i>Results:</i> The analysis included more than 2.5 million beneficiaries (56% women; mean age: 78 years; 87% white; n = 957,933 for 1994–1996; n = 838,330 for 1996–1999; n = 895,916 for 2000–2002) aggregated to all 3,118 US counties. After adjustment for changing patient demographics and comorbidities, there was a 4.5% decrease in recurrent stroke rates from 1994–1996 (13.2%) to 2000–2002 (12.6%; p for trend &lt;0.0001). The geographic and temporal patterns were not uniform; the recurrent stroke rates decreased within sections of the Southeast (the ‘stroke belt’), but increased in counties in the middle and western sections of the USA. <i>Conclusions:</i> The overall recurrent ischemic stroke rates declined by almost 5% from 1994 to 2002, but temporal patterns varied markedly by region. Additional research is needed to identify the reasons for this geographic disparity.

<i>背景与目的：</i>美国每年发生的79.5万例脑卒中中，超过20%为复发性事件。目前针对美国复发性脑卒中发生率随时间的变化趋势，相关研究仍较为匮乏。本研究旨在明确1994年至2002年间，美国各县老年人群1年内缺血性脑卒中复发率的全国性变化趋势。
<i>方法：</i>本研究针对所有按服务项目付费的医疗保险（Medicare）受益人中，首发缺血性脑卒中（对应国际疾病分类第9版ICD-9编码433、434、436）后的1年复发率，按美国各县分别统计了1994-1996年、1997-1999年及2000-2002年三个时段的数据。研究采用贝叶斯时空泊松模型（Bayesian spatiotemporal Poisson modeling），针对人口统计学特征、病史及合并症进行风险校正后，分析各县复发性脑卒中发生率随时间变化的特异性趋势。
<i>结果：</i>本研究共纳入超过250万名受益人（其中女性占56%，平均年龄78岁，白人占87%；1994-1996年亚组n=957933，1997-1999年亚组n=838330，2000-2002年亚组n=895916），数据覆盖美国全部3118个县。在校正患者人口统计学特征及合并症的变化后，复发性脑卒中发生率从1994-1996年的13.2%下降至2000-2002年的12.6%，降幅达4.5%（趋势检验p<0.0001）。研究发现地理与时间模式并不均一：美国东南部（即"脑卒中带"）部分区域的复发性脑卒中发生率有所下降，而美国中部及西部各县的该发生率则呈上升趋势。
<i>结论：</i>1994年至2002年间，美国整体缺血性脑卒中复发率下降了近5%，但不同区域的时间变化模式存在显著差异。未来仍需开展进一步研究以明确该地理差异的成因。