Abstract
BACKGROUND: To investigate the impact of disease severity on exacerbation patterns and identify its potential as a risk factor for future exacerbations in patients admitted for asthma exacerbations. METHODS: We analyzed frequency and time to next exacerbation over a period of three years in 532 patients admitted for exacerbation. Disease severity was selected as a potential risk factor for the events. Kaplan-Meier analysis was used to identify the probability of future exacerbations. A Cox-proportional hazards model was used to assess independent relative risks. RESULTS: Out of 532 patients analyzed, the frequency of exacerbations rose as the severity of the asthma increased. The exacerbation rates in the following year were 1.66 per person for patients with mild asthma and 3.98 for patients with severe asthma. The median time to the next exacerbation in patients with mild asthma was 61.4 weeks (95% CI, 40.1-82.6) compared to 15.0 weeks (95% CI, 11.3-18.6) in patients with severe asthma (p<0.001). Multivariate analysis showed that asthma severity (severe vs mild asthma, HR=1.42, 95% CI, 1.07-1.89), a history of 1-2 exacerbations (HR=1.95, 95% CI, 1.45-2.63) or > 2 exacerbations (HR=2.32, 95% CI, 1.56-3.44) in the previous 12 months, and a high number of comorbidities (≥5 vs none, HR=2.5, 95% CI, 1.41-4.45) were independent predictors of the probability of future exacerbations. CONCLUSION: Asthma severity is a strong independent risk factor for future exacerbations, and exacerbation rates also become more frequent as the severity of the asthma increases. These findings help in better understanding of the natural course of exacerbations across the spectrum of asthma disease severity.