Yu Z et al. Lancet Reg Health Eur. 2025; DOI: 10.1016/j.lanepe.2025.101314.
Summary
Background
The joint impact of exposure to multiple urban environmental factors on asthma remains unclear.
Methods
We analysed data from 14 European cohorts to assess the impact of the urban exposome on asthma incidence across the life course. We linked three external exposome domains (air pollution, built environment, ambient temperature) to the participants’ home addresses at baseline. We performed k-means clustering within each domain and assessed associations of clusters with asthma adjusting for potentially relevant covariates in cohort-specific analyses, with subsequent separate meta-analyses for birth and adult cohorts. An environmental risk score using a coefficient-weighted sum approach was used to assess the impact of combining the three domains.
Findings
A total of 7428 incident asthma cases were identified among 349,037 participants (from birth up to age 70+). Overall, we observed higher risks of asthma for clusters characterized by high particulate matter and nitrogen dioxide exposure in adults (ORmeta = 1.13, 95%CI:1.01–1.25), and clusters characterized by high built-up area and low levels of greenness in both children and adults (ORmeta = 1.36, 95%CI: 1.14–1.64 for birth cohorts and ORmeta = 1.15, 95%CI: 1.03–1.28 for adult cohorts, respectively). The joint exposure using the environment risk score combining the three domains was consistently associated with higher risks of incident asthma (ORmeta = 1.13, 95%CI: 1.07–1.20 for birth cohorts, ORmeta = 1.15, 95%CI: 1.10–1.20 for adult cohorts per 20% increase). On average 11.6% of the incident asthma cases could be attributed to environmental risk score above cohort-specific median levels.
Interpretation
Multiple environmental exposures jointly contribute to incident asthma risk across the life course. Urban planning accounting for these factors may help mitigate asthma development.
Research in context
Evidence before this study
Several environmental exposures have been identified as risk factors for asthma onset. However, most evidence comes from single-exposure analyses, which fail to capture the complex, real-life patterns of multiple exposures. We searched PubMed and Web of Science for peer reviewed studies using the search term ((“Exposure” and “Environment”) AND (“Exposome”)) AND (“Asthma” and “Epidemiology”) from inception up to September 30th, 2024. Only three studies have reported the association between multiple environmental exposures and asthma using exposomic approaches. Two studies were limited to a single cohort with cross-sectional analysis, and one combined data from six cohorts; they varied in their exposure assessment methods, and focused solely on asthma-related prevalence outcomes, rather than asthma incidence.
Added value of this study
This study analysed data from 14 European cohorts with harmonized exposure assessments. We included asthma incidence data across the lifespan, from birth to old age, and leveraged this data for longitudinal analyses. To address the complexity of real-life exposure patterns, we applied clustering methods to evaluate the joint associations of multiple environmental exposures.
Implications of all the available evidence
Our finding provides evidence that multiple environmental exposures jointly contribute to incident asthma risk across the life course. Integrating these factors into urban planning and policy development may help mitigate asthma onset and promote healthier living environments.