INTRODUCTION It is unknown if high concentration of airborne grass pollen, where subtropical grasses (Chloridoideae and Panicoideae) dominate, is a risk factor for respiratory health. Here we systematically reviewed the association between airborne grass pollen exposure and asthma emergency department (ED) presentations and hospital admissions in subtropical climates. OBJECTIVES A systematic review was performed to identify and summarise studies that reported on respiratory health (asthma ED presentations and hospital admissions) and airborne grass pollen exposure in subtropical climates. METHODS Searches were conducted in: MEDLINE, Web of Science, Scopus, CINAHL (EBSCO), Embase and Google Scholar databases (1966-2019). Risk of bias was assessed using a validated quality assessment tool. A meta-analysis was planned, however due to the heterogeneity in study design it was determined inappropriate and instead a narrative synthesis was undertaken. RESULTS Nineteen studies were identified for inclusion, with a total of 598,931 asthma ED presentation participants and 36,504 asthma hospital admission participants in six countries (Australia, India, Israel, Italy, Spain, USA). The narrative synthesis found airborne grass pollen appears to have a small and inconsistent increase on asthma ED presentations (judged as: probably little effect n = 5, may have little effect n = 4, no effect n = 2 and uncertain if there is an effect n = 4) and hospital admissions (judged as: probably increase slightly n = 2 probably little effect n = 1, may have a little effect n = 1, no effect n = 3 and we are uncertain if there is an effect n = 4) in the subtropics. Furthermore, the reported effect sizes were small and its clinical relevance may be difficult to discern. CONCLUSION Exposure to airborne grass pollen appears to have a small and inconsistent increase on asthma ED presentations and hospital admissions in the subtropics. These findings are comparable to reported observations from studies undertaken in temperate regions.

中文翻译：

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草花粉是亚热带地区急诊科报告和呼吸系统疾病住院的起因：系统综述。

引言目前，高浓度的空气传播草粉是否是呼吸系统健康的危险因素，其中亚热带草（绿藻科和Pan科）占主导地位。在这里，我们系统地回顾了亚热带气候中空气中的草粉花粉暴露与哮喘急诊科（ED）的报告和住院情况之间的关联。目的进行系统的审查，以鉴定和总结有关亚热带气候中呼吸健康（哮喘ED表现和住院情况）和空气中草粉花粉暴露的报告。方法在MEDLINE，Web of Science，Scopus，CINAHL（EBSCO），Embase和Google Scholar数据库（1966-2019）中进行搜索。使用经过验证的质量评估工具评估了偏倚风险。计划进行荟萃分析，然而，由于研究设计的异质性，它被认为是不合适的，而是进行了叙述性的综合。结果确定了19项纳入研究，在六个国家（澳大利亚，印度，以色列，意大利，西班牙，美国）共有598,931名哮喘ED参加者和36,504名哮喘住院患者参加了研究。叙述性综合发现，空气中的草花粉似乎对哮喘ED表现有较小且不一致的增加（判断为：可能无效n = 5，可能无效n = 4，无效n = 2且不确定是否有效n = 4）和住院（判断为：可能略有增加n = 2可能影响不大n = 1，可能影响不大n = 1，没有影响n = 3，我们不确定是否有影响n = 4 ）。此外，报道的效应量很小，其临床相关性可能难以辨别。结论在亚热带地区，暴露于空气中的草花粉似乎与哮喘ED表现和住院人数的增加并不一致。这些发现与在温带地区进行的研究报告的观察结果相当。