Asthma and severe acute respiratory infections: a stratified analysis of mortality patterns in Brazil.

purposeAsthma is a prevalent chronic respiratory condition. However, evidence on its association with mortality from severe acute respiratory infections (SARI), including COVID-19, remains scarce in South America, particularly in Brazil. Given asthma's potential to influence respiratory outcomes, we investigated how age and other demographic or clinical predictor variables are associated with mortality in this context.

methodsWe analyzed SARI mortality data from 415,711 patients recorded in the Brazilian Unified Health System between January and December 2022. Patients were stratified by key predictors such as asthma status, age group, intensive care unit admission, and sex. Both frequentist and Bayesian logistic regression models were fitted to explore interactions among these predictors. To address class imbalance (fewer deaths relative to recoveries), we applied data-balancing techniques before model estimation.

resultsOlder age and admission to an intensive care unit were strong predictors of death. Invasive mechanical ventilation emerged as the single strongest clinical marker of severity, with an adjusted odds ratio (OR) of approximately 14.7, though this was exceeded by the effect of age, whose influence on mortality was even greater. Asthma was associated with lower mortality overall (adjusted OR ≈ 0.31), although the protective association weakened in young adults aged 19-29 years (OR ≈ 0.69) and in adults aged [Formula: see text] years (OR ≈ 0.72). Vaccination against COVID-19 or influenza, as well as the use of antivirals, were each linked to lower mortality. The final model showed good discrimination, with an area under the receiver operating characteristic curve of 0.845.

conclusionAsthma is associated with lower odds of death, but the strength of this protective association diminishes in early adulthood and again in later life. These age-related differences warrant further investigation and, if confirmed, could inform age-tailored care strategies. Maintaining broad vaccine coverage and timely antiviral use remains advisable for all patients. Future studies that incorporate detailed information on asthma control, medication adherence and lifestyle factors are needed to clarify the mechanisms underlying these patterns.