Risk factors of severe adult-onset asthma: a multi-factor approach

Abstract Background The aim was to identify risk factors of severe adult-onset asthma. Methods We used data from 1350 population-based asthmatics (Adult Asthma in Finland) with adult-onset asthma (age range 31-93 years) from Finnish national registers. Severe asthma was defined as self-reported severe asthma AND asthma symptoms causing much harm AND regular impairment AND (≥1 oral corticosteroid course/year OR regular oral corticosteroids OR wake up in the night due to asthma symptoms/wheezing attach ≥ a few times/month). Sixteen covariates covering several domains (personal characteristics, education, life-style, early life factors, asthma characteristics and multimorbidities) were selected based on literature and were studied in association with severe asthma using logistic regressions. Results The study population included 100 (7.4%) individuals with severe asthma. In a univariate analysis, severe asthma was associated with male sex, age, low education, no professional training, ever smoking, ≥ 2 siblings, ≥ 1 chronic comorbidity and Non-steroidal anti-inflammatory drug (NSAID) -exacerbated respiratory disease (NERD) (p<0.05); and trends for association (p<0.2) were observed for severe childhood infection, presence of chronic rhinosinusitis with nasal polyps, and being the 1 st child. The 10 variables (being 1 st child was removed due to multicolinearity) were thus entered in a multivariate regression model and severe asthma was significantly associated with male sex (OR [CI95%] = 1.96 [1.16-3.30]), ever smoking (1.98 [1.11-3.52]), chronic comorbidities (2.68 [1.35-5.31]), NERD (3.29 [1.75-6.19]), and ≥ 2 siblings (2.51 [1.17-5.41]). There was a dose-response effect of the total sum of these five factors on severe asthma (OR [CI95%] = 2.30 [1.81-2.93] for each increase of one unit of the score). Conclusions Male sex, smoking, NERD, comorbidity, age and number of siblings were independent risk factors for self-reported severe asthma. The effects of these factors seem to be additive; each additional risk factor gradually increase with the risk of severe asthma.