Outdoor air pollutants and asthma risk in adolescents: evidence from a systematic review and meta-analysis
Abstract
Background: Existing epidemiological evidence linking outdoor air pollution to asthma incidence in adolescents remains inconclusive, due to methodological heterogeneity in study design, exposure assessment, and asthma case definitions.
Methods: This systematic review and meta-analysis synthesized observational studies examining associations between outdoor air pollutants and adolescent asthma. Comprehensive searches of PubMed, Embase, and Scopus were conducted using Medical Subject Headings (MeSH) and free-text terms. Eligible studies reported quantitative estimates, odds ratio (OR), hazard ratio (HR), relative risk (RR), prevalence ratio (PR), incidence rate ratio (IRR), or prevalence odds ratio (POR), with corresponding 95% confidence interval (CI). Pooled estimates were calculated using inverse-variance weighted fixed- and random-effects models. Heterogeneity was assessed using Cochran's Q and I 2 statistics.
Results: Of 51 eligible studies, 40 were incorporated into the meta-analysis. Statistically significant associations were identified for each 10 μg/m3 increase in nitrogen dioxide (NO₂) (adjusted odds ratio [aOR] = 1.18; 95% CI: 1.08-1.29) and ozone (O₃) (aOR = 1.01; 95% CI: 1.00-1.03), as well as per 1 ppm increase in carbon monoxide (CO) (aOR = 1.31; 95% CI: 1.08-1.53). Traffic-related air pollution (TRAP) was also significantly associated with an elevated risk (aOR = 1.15; 95% CI: 1.10-1.21). In contrast, the pooled estimate for particulate matter with diameter ≤…
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