Ozone is associated with health impacts including respiratory outcomes; however, results differ across studies. Meta-analysis is an increasingly important approach to synthesizing evidence across studies. We conducted meta-analysis of short-term ozone exposure and respiratory hospitalizations to evaluate variation across studies and explore some of the challenges in meta-analysis. We identified 136 estimates from 96 studies and investigated how estimates differed by age, ozone metric, season, lag, region, disease category, and hospitalization type. Overall results indicate associations between ozone and various types of respiratory hospitalizations; however, study characteristics affected risk estimates. Estimates were similar, but higher, for the elderly compared to all ages and for previous day exposure compared to same day exposure. Comparison across studies was hindered by variation in definitions of disease categories, as some (e.g., asthma) were identified through ≥3 different sets of ICD codes. Although not all analyses exhibited evidence of publication bias, adjustment for publication bias generally lowered overall estimates. Emergency hospitalizations for total respiratory disease increased 4.47% (95% interval 2.48, 6.50%) per 10ppb 24-hr ozone among the elderly without adjustment for publication bias and 2.97% (1.05, 4.94%) with adjustment. Comparison of multi-city study results and meta-analysis based on single-city studies further suggested publication bias.

中文翻译：

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短期暴露于环境臭氧与呼吸系统住院之间关联的荟萃分析

臭氧与健康影响有关，包括呼吸系统后果；然而，不同研究的结果不同。荟萃分析是一种越来越重要的跨研究综合证据的方法。我们对短期臭氧暴露和呼吸道住院治疗进行了荟萃分析，以评估研究之间的差异并探讨荟萃分析中的一些挑战。我们从 96 项研究中确定了 136 项估计值，并调查了估计值如何因年龄、臭氧指标、季节、滞后、地区、疾病类别和住院类型而异。总体结果表明臭氧与各种类型的呼吸系统住院之间存在关联；然而，研究特征影响了风险估计。与所有年龄段相比，老年人的估计值相似，但更高，前一天暴露与同一天暴露相比，估计值更高。不同研究之间的比较因疾病类别定义的差异而受阻，因为有些（例如，哮喘）是通过 ≥ 3 组不同的 ICD 代码确定的。尽管并非所有分析都显示出发表偏倚的证据，但对发表偏倚的调整通常会降低总体估计值。在未调整发表偏倚的情况下，老年人中每 10ppb 24 小时臭氧因总呼吸系统疾病急诊住院增加 4.47%（95% 间隔 2.48, 6.50%），调整后增加 2.97%（1.05, 4.94%）。多城市研究结果的比较和基于单城市研究的荟萃分析进一步表明了发表偏倚。尽管并非所有分析都显示出发表偏倚的证据，但对发表偏倚的调整通常会降低总体估计值。在未调整发表偏倚的情况下，老年人中每 10ppb 24 小时臭氧因总呼吸系统疾病急诊住院增加 4.47%（95% 间隔 2.48, 6.50%），调整后增加 2.97%（1.05, 4.94%）。多城市研究结果的比较和基于单城市研究的荟萃分析进一步表明了发表偏倚。尽管并非所有分析都显示出发表偏倚的证据，但对发表偏倚的调整通常会降低总体估计值。在未调整发表偏倚的情况下，老年人中每 10ppb 24 小时臭氧因总呼吸系统疾病急诊住院增加 4.47%（95% 间隔 2.48, 6.50%），调整后增加 2.97%（1.05, 4.94%）。多城市研究结果的比较和基于单城市研究的荟萃分析进一步表明了发表偏倚。