Change in exacerbation rate of asthma patients before and after COVID-19 infection.

Background: COVID-19 had significant impact on healthcare utilization and disease outcomes worldwide. While overall asthma exacerbations reportedly declined during the pandemic, the specific effect of COVID-19 infection on subsequent exacerbation patterns in asthma patients remains unclear.

Methods: Using a nationwide health insurance claims database from South Korea, we identified patients who had both asthma and a confirmed COVID-19 diagnosis in 2020. We defined the pre-COVID-19 period as the 12 months immediately preceding the date of each patient's COVID-19 diagnosis, and the post-COVID-19 period as the 12 months following that date. Baseline characteristics, annual exacerbation rates, and direct medical costs were compared between these two time frames.

Results: Among 82,825 confirmed COVID-19 cases, 2,965 patients with asthma met the inclusion criteria. Compared to the pre-COVID-19 period, the proportion of patients experiencing moderate and moderate-to-severe exacerbations decreased, whereas severe exacerbations increased after COVID-19 infection. In a binomial mixed model, moderate and moderate-to-severe exacerbations declined significantly (IRR=0.848, p<0.001 and IRR=0.912, p<0.001, respectively), but severe exacerbations increased (IRR=1.220, p<0.001) after COVID-19 infection. Of those who were non-exacerbators prior to COVID-19, 10.8% became exacerbators. This group was older, more frequently male, and had a greater comorbidity burden. Total direct medical costs escalated markedly from USD 2,965.50 to USD 4,850.41 (p<0.001), particularly among those who developed as exacerbators after COVID-19 infection.

Conclusions: COVID-19 infection had a paradoxical impact on asthma exacerbations, reducing moderate exacerbations but increasing severe events. The substantial rise in medical costs contributes the economic burden of asthma care.