Air pollution exposure is associated with rhinitis in older US adults via specific immune mechanisms

Pathophysiology of rhinitis in older adults is largely unknown. We tested whether air pollution is associated with this condition and how immune mechanisms may play a role in this relationship.

We analyzed cross-sectional data from the National Social Life, Health, and Aging Project, a nationally representative study of older adults born between 1920 and 1947. Particulate matter ≤2.5 μm (PM_2.5 ) air pollution exposure estimates were generated using validated spatiotemporal models. Presence of rhinitis was defined based on medication use (≥1: intranasal medications: steroids, antihistamines, lubricants, and/or decongestants, and/or oral medications: antihistamines and/or decongestants). K-means cluster analysis (Jaccard method) was used to group 13 peripheral blood cytokines into 3 clusters to facilitate functional determination. We fitted multivariate logistic regressions to correlate PM_2.5 exposure with presence of rhinitis, controlling for confounders, and then determined the role of cytokines in this relationship.

Long- (but not short-) term exposure to PM_2.5 was associated with presence of rhinitis: 3-year exposure window, odds ratio (OR) = 1.32, 95% confidence interval (CI): 0.98, 1.80, per 1 standard deviation (SD) PM_2.5 increase. Inclusion of cytokine cluster in the model led to a modestly stronger effect of PM_2.5 exposure on rhinitis (OR = 1.37; 95% CI: 1.00, 1.87; 3-year exposure window). The particular immune profile responsible for this result was composed of elevated IL-3, IL-12, and IFN-γ (OR = 4.86, 95% CI: 1.10, 21.58, immune profile-PM_2.5 exposure interaction term).

We show for the first time that IL-3, IL-12, and IFN-γ explain in part the relationship between PM_2.5 exposure and rhinitis in older US adults. If confirmed, these immune pathways may be used as therapeutic targets.