Uncontrolled Asthma and Severe COVID-19: A Prospective Bidirectional Risk Analysis

Asthma control is multifaceted, involving symptoms and risk of adverse outcomes. Emerging evidence suggests a bidirectional link between poor asthma control and severe COVID-19, but large studies addressing all components of asthma control in this context are lacking. Our aims were to evaluate if 1) uncontrolled asthma was a risk factor for COVID-19 hospitalization and death, 2) asthma control changed during the pandemic and 3) COVID-19 hospitalization was a risk factor for future uncontrolled asthma.

Patients with asthma (n = 125,362) were identified in the Swedish National Airway Register from January 2014 to 2020, whereof n = 2377 were hospitalized and n = 305 died due to COVID-19 during follow-up until December 2022. Asthma control was evaluated by symptoms (Asthma Control Test (ACT) ≥ 20: well controlled, ACT 16-19 not well-controlled and ACT < 16 very poorly controlled asthma), lung function (FEV₁% predicted (pp)) and frequent and/or severe exacerbations (dispensed oral corticosteroids and asthma inpatient care).

ACT 16-19 (RR 1.57, 95% CI 1.34-1.84), ACT < 16 (1.72, 1.46-2.02), FEV₁ < 80pp (1.29, 1.13-1.48), frequent (1.99, 1.79-2.21) and severe exacerbations (2.54, 2.09-3.08) were associated with a higher risk for COVID-19 hospitalization. COVID-19 death was associated with ACT < 16, frequent and severe exacerbations. Overall, at follow-up, proportions of ACT < 20 (36.1%) and FEV₁ < 80pp (48.3%) were stable, while exacerbations decreased (frequent; 7.9% to 6.8%, severe; 1.3% to 0.4%). COVID-19 hospitalization was a risk factor for frequent (1.35, 1.22-1.51) and severe (3.42, 1.22-1.51) future asthma exacerbations.

All dimensions of poor asthma control were associated with an increased risk of severe COVID-19. In contrast, only exacerbation risk was elevated following COVID-19.