Comorbidities and elevated IL-6 associate with negative outcome in adult-onset asthma

The effect of systemic inflammation and comorbidities on treatment and outcome of adult-onset asthma remains unknown and is the objective of this study.As part of the Seinäjoki Adult Asthma Study (SAAS) with a 12-year follow-up, serum interleukin (IL)-6, high-sensitivity C-reactive protein (hsCRP) and lung function were measured and clinical information on comorbidities and medication collected from 170 patients with adult-onset asthma without chronic obstructive pulmonary disease.At follow-up visit, 54% of the patients had systemic inflammation as indicated by elevated IL-6 or hsCRP, 58% had at least one comorbidity and 30% at least two comorbidities (other than asthma related). Patients with systemic inflammation were treated with higher dose of inhaled corticosteroid (ICS) and they had lower lung function and higher blood neutrophils compared with patients without. Patients having ≥2 comorbidities had lower Asthma Control Test score and this association remained significant in adjusted analysis. Patients with both systemic inflammation and comorbidities showed poorest outcome of asthma. In multivariate regression analysis, high ICS dose was predicted by elevated IL-6, elevated blood neutrophils and eosinophils and poorer lung function at baseline and follow-up.Altogether, in patients with adult-onset asthma, elevated IL-6 was associated with use of high-dose ICS while multi-morbidity was linked to worse symptoms of asthma.