Supplementary Material for: Case Fatality Rates of Subarachnoid Hemorrhage Are Decreasing with Substantial between-Country Variation: A Systematic Review of Population-Based Studies between 1980 and 2020

<b><i>Background:</i></b> The declining prevalence of smoking and hypertension has been associated with the decrease of subarachnoid hemorrhage (SAH) incidence in the 21st century. Since these same risk factors are linked to SAH mortality, the case fatality rate (CFR) of SAH has potentially also decreased during recent decades. Thus, we conducted a systematic review to address SAH CFR changes over the last 40 years. <b><i>Methods:</i></b> We performed a systematic literature search in OVID Medline, Scopus, and Cochrane Library databases. We focused on population-based studies published between 1980 and 2020 that had included both hospitalized and nonhospitalized SAH cases, and reported 1-month CFRs for at least two individual study periods for the same population. Finally, we used a linear regression analysis to estimate the annual CFR changes in each identified population and pooled the regional changes for larger geographical and sex-specific analyses. <b><i>Results:</i></b> Of the 4,562 initial publications, we included 22 studies (three of which reached a high-quality classification) consisting of 17,593 SAH patients from 16 different populations and 10 countries. Between 1980 and 2020, SAH CFR declined in all but two populations by an average of −1.5%/year. In the continent-based pooled geographical analyses, CFR decline was the most noticeable in North America (−2.4%/year) and Oceania (−2.2%/year). The decline was more moderate in Northern Europe (−0.8%/year) and Southern Europe (−0.7%/year). Overall, CFRs declined both in women (−1.9%/year) and in men (−1.2%/year). When comparing the first and second half of the study period, CFRs declined from 41% to 31%. <b><i>Conclusion:</i></b> Short-term SAH CFRs seem to have declined since 1980. Time trends of SAH CFRs can still be identified for only a few populations, and high-quality data are scarce. Whether the observed decline relates to changes in risk factors, treatment outcomes or diagnostics remains to be studied.

<b><i>背景：</i></b> 21世纪以来，吸烟与高血压的患病率持续下降，与蛛网膜下腔出血（subarachnoid hemorrhage, SAH）发病率的降低密切相关。鉴于上述危险因素同样与SAH患者的病死率相关，近数十年来SAH的病死率（case fatality rate, CFR）或也呈下降趋势。因此，本研究开展了一项系统综述，旨在探讨近40年来SAH病死率的变化趋势。
<b><i>方法：</i></b> 我们在OVID Medline、Scopus及Cochrane Library数据库中进行了系统性文献检索。纳入1980年至2020年间发表的基于人群的研究，此类研究需同时涵盖住院与非住院的SAH病例，且针对同一人群至少报告了两个独立研究时段的1个月病死率。最终，我们采用线性回归分析估算每个纳入人群的年病死率变化率，并合并区域数据以开展更大范围的地理及性别特异性分析。
<b><i>结果：</i></b> 在最初检索到的4562篇文献中，最终纳入22项研究（其中3项为高质量研究），涵盖来自10个国家16个人群的17593例SAH患者。1980年至2020年间，除两个人群外，其余所有人群的SAH病死率均呈下降趋势，年均降幅达1.5%。基于大洲的合并地理区域分析显示，北美洲（年均降幅2.4%）及大洋洲（年均降幅2.2%）的病死率下降最为显著；北欧（年均降幅0.8%）与南欧（年均降幅0.7%）的降幅则较为平缓。总体而言，女性（年均降幅1.9%）与男性（年均降幅1.2%）的SAH病死率均有所下降。将研究时段分为前后两半进行比较可见，SAH病死率从41%降至31%。
<b><i>结论：</i></b> 1980年以来，SAH的短期病死率似乎呈下降趋势。但目前仅在少数人群中仍可明确SAH病死率的时间趋势，且高质量数据较为匮乏。本次观察到的病死率下降是否与危险因素、治疗结局或诊断技术的变化相关，仍有待进一步研究。