Relationship between airway inflammation and airflow limitation in elderly asthmatics

BACKGROUND: The prevalence of asthma in elderly population has been increasing. Previous studies have demonstrated clinical characteristics of elderly asthmatics (EA). However, little is known regarding the influence of immunological change on the physiological status of EA. OBJECTIVE: We investigated the relationship between inflammatory mediators and the pulmonary function (PF) of EA. METHODS: Eligible adult asthmatics recruited from the Allergy Center of Saitama Medical University Hospital were classified into a non-EA group (<40 years old, n = 15) and an EA group (≥60 years old, n = 43). Sputum induction and PF tests were performed. Concentrations of an eosinophil-derived neurotoxin (EDN) and neutrophil elastase (NE) in sputum supernatants were measured by enzyme-linked immunosorbent assay and a fluorometric assay using a commercial assay kit, respectively. Cell counts and EDN and NE concentrations in sputum were compared between the 2 groups. The association among those parameters and PF were analyzed in each group. RESULTS: The EA group had a significantly higher severe asthmatics proportion (p = 0.01), a lower current smokers proportion (p = 0.002), lower sensitization rate to aeroallergens (p = 0.012), several PFs deterioration (p < 0.0001) and lower total IgE levels (p = 0.001) than the non-EA group. Sputum neutrophil counts and NE concentrations were significantly higher in the EA group than those in the non-EA group (median neutrophil: 4.11 vs. 2.74 ×10(5)/mL, p = 0.03; NE: 2.0 vs.1.6 µg/mL, p < 0.05, respectively), whereas sputum eosinophil counts and EDN concentrations were not. Sputum EDN concentrations were significantly positively correlated with sputum neutrophil counts (r = 0.39, p = 0.031) and NE concentrations (r = 0.57, p < 0.0001) only in the EA group. Eosinophil-related parameters were negatively correlated with several PFs in the 2 groups. Neutrophil-related parameters were negatively correlated with PFs only in the non-EA group. CONCLUSION: This study determines that in EA, persistent active eosinophilic airway inflammation is accompanied by advanced neutrophilic inflammation, which may contribute to deteriorated PF. This distinct airway inflammation may increase the severity of asthma in EA.