IL-1Rahigh-IL-4low-IL-13low: A Novel Plasma Cytokine Signature Associated with Olfactory Dysfunction in Older US Adults.

Inflammation has been implicated in physical frailty, but its role in sensory impairment is unclear. Given that olfactory impairment predicts dementia and mortality, determining the role of the immune system in olfactory dysfunction would provide insights mechanisms of neurosensory decline. We analyzed data from the National Social Life, Health and Aging Project, a representative sample of home-dwelling older US adults. Plasma levels of 18 cytokines were measured using standard protocols (Luminex xMAP). Olfactory function was assessed with validated tools (n-butanol sensitivity and odor identification, each via Sniffin' Sticks). We tested the association between cytokine profiles and olfactory function using multivariate ordinal logistic regression, adjusting for age, gender, race/ethnicity, education level, cognitive function, smoking status, and comorbidity. Older adults with the IL-1Rahigh-IL-4low-IL-13low cytokine profile had worse n-butanol odor sensitivity (odds ratio [OR] = 1.61, 95% confidence interval [CI] 1.19-2.17) and worse odor identification (OR = 1.42, 95% CI 1.11-1.80). Proinflammatory, Th1, or Th2 cytokine profiles were not associated with olfactory function. Moreover, accounting for physical frailty did not alter the main findings. In conclusion, we identified a plasma cytokine signature-IL-1Rahigh-IL-4low-IL-13low-that is associated with olfactory dysfunction in older US adults. These data implicate systemic inflammation in age-related olfactory dysfunction and support a role for immune mechanisms in this process, a concept that warrants additional scrutiny.

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

BACKGROUND: 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. METHODS: 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 (PM2.5 ) 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 PM2.5 exposure with presence of rhinitis, controlling for confounders, and then determined the role of cytokines in this relationship. RESULTS: Long- (but not short-) term exposure to PM2.5 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) PM2.5 increase. Inclusion of cytokine cluster in the model led to a modestly stronger effect of PM2.5 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-PM2.5 exposure interaction term). CONCLUSION: We show for the first time that IL-3, IL-12, and IFN-γ explain in part the relationship between PM2.5 exposure and rhinitis in older US adults. If confirmed, these immune pathways may be used as therapeutic targets.