The association of asthma with COVID-19 mortality: an updated meta-analysis based on adjusted effect estimates

Background The association of asthma to the risk of mortality among coronavirus disease 2019 (COVID-19) patients is not clear. Objective The purpose of this study was to investigate the association between asthma and the risk of mortality among COVID-19 patients. Methods Systematic searches were performed through electronic databases including PubMed, EMBASE and Web of Science to identify the potential articles reporting adjusted effect estimates on the association of asthma with fatal COVID-19. A random-effects model was conducted to estimate the pooled effects. Sensitivity analysis, subgroup analysis, meta-regression, Begg’s test and Egger’s test were also performed. Results The overall results based on sixty-two studies with 2,457,205 cases reporting adjusted effect estimates demonstrated that COVID-19 patients with asthma had a significantly reduced risk of mortality compared with those without (15 cohort studies-829,670 patients, pooled hazard ratio (HR) = 0.88, 95% confidence interval (CI) [0.82-0.95], I2 = 65.9%, P < 0.001; 34 cohort studies-1,008,015 patients, pooled odds ratio (OR) = 0.88, 95% CI [0.82-0.94], I2 = 39.4%, P = 0.011; 11 cross-sectional studies-1,134,738 patients, pooled OR = 0.87, 95% CI [0.78-0.97], I2 = 41.1%, P = 0.075). Subgroup analysis based on the types of adjusted factors indicated that COVID-19 patients with asthma had a significantly reduced risk of mortality among studies adjusting for demographic, clinical and epidemiologic variables (pooled OR = 0.87, 95% CI [0.83-0.92], I2 = 36.3%, P = 0.013; pooled HR = 0.90, 95% CI [0.83-0.97], I2 = 69.2%, P < 0.001), but not among studies only adjusting for demographic variables (pooled OR = 0.88, 95% CI [0.70-1.12], I2 = 40.5%, P = 0.097; pooled HR = 0.82, 95% CI [0.64-1.06], I2 = 0%, P = 0.495). Sensitivity analysis proved that our results were stable and robust. Both Begg’s test and Egger’s test indicated that potential publication bias did not exist. Conclusion Our data based on adjusted effect estimates indicated that asthma was significantly related to a reduced risk for COVID-19 mortality.