摘要：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 kinds 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 by 4.47% (95% interval: 2.48, 6.50%)
per 10 ppb 24 h 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.
