Long-term ozone exposure and asthma: a systematic review and meta-analysis

Abstract

Abstract Background Ambient air pollution, particularly surface ozone, is a significant global health concern, with 9 out of 10 people exposed to levels exceeding WHO guidelines. This exposure is linked to approximately 7 million premature deaths annually, a number expected to double by 2050. While the effects of short-term exposure to ozone on exacerbation of asthma symptoms and mortality are well-documented, the impact of long-term exposure remains unclear. Aim This systematic literature review aims to quantify the association between long-term exposure to ozone and asthma incidence and prevalence and derive an exposure-response relationship. Methods International electronic databases, including PubMed, Embase, Cochrane Central Register of Controlled Trials, and Web of Science, were searched, supplemented by grey literature sources such as Google Scholar and WHO - Global Index Medicus from conception to July 31, 2023. Observational epidemiological cohort, case-control, or cross-sectional studies reporting quantitative associations between exposure and outcome were included. Meta-analysis will synthesize effect size estimates using a Meta-Regression - Bayesian, Ensemble, Regularized, Trimmed (MR-BRT) model. Results A total of 5,947 titles were initially identified from databases, and following the removal of duplicates, 3,235 titles and abstracts were screened, resulting in 84 articles deemed eligible for full-text review. The full-text screening identified 29 studies comprising 38 articles. A comprehensive overview of the included studies will be provided. We will describe the study settings, design, and measurement methods used by the identified studies. Furthermore, results of the MR-BRT model will be summarized, and exposure-response functions will be discussed. Funding: This work is part of the BEST-COST project which is funded by the European Union’s Horizon Europe programme under Grant Agreement No.101095408. Key messages • This research fills the gap in understanding the association between long-term exposure to ambient ozone and asthma incidence and prevalence. • Developing exposure-response functions would enable estimation of the disease burden associated with long-term ozone exposure.