Different Impacts of Traffic-Related Air Pollution on Early-Onset and Late-Onset Asthma

Background: Early-onset asthma (EOA) and late-onset asthma (LOA) are two distinct phenotypes. Air pollution has been associated with an increase in poorer asthma outcomes. The objective of this study was to examine the effects of traffic-related air pollution (TRAP) on asthma outcomes in EOA and LOA patients.
Methods: A cross-sectional study was conducted on 675 asthma patients (LOA: 415) recruited from a major medical center in Taiwan. The land-use regression (LUR) model was used to estimate the level of exposure to PM₁₀, PM_2.5, NO₂, and O₃ on an individual level. We investigated the association between TRAP and asthma outcomes in EOA and LOA patients, stratified by allergic sensitization status, using a regression approach.
Results: An increase in PM₁₀ was associated with younger age of onset, increased asthma duration, and decreased lung function in EOA patients (p< 0.05). An increase in PM₁₀ was associated with older age of onset, and decreased asthma duration, eosinophil count, and Asthma Control Test (ACT) score in LOA patients. An increase in PM_2.5 was associated with younger age of onset, increased asthma duration, decreased eosinophil count, and lung function in EOA patients (p< 0.05). An increase in PM_2.5 was associated with decreased lung function and ACT score in LOA patients. An increase in NO₂ was associated with increased eosinophil count and decreased lung function in EOA patients (p< 0.05). An increase in O₃ was associated with decreased lung function in LOA patients (p< 0.05). In addition, associations of TRAP with age of onset and eosinophil counts were mainly observed in both EOA and LOA patients with allergic sensitization, and an association with ACT was mainly observed in LOA patients without allergic sensitization.
Conclusion: The impact of TRAP on age of onset, eosinophil count, and lung function in EOA patients, and ACT in LOA patients, was affected by the status of allergic sensitization.