Biomarkers and Risk Factors Associated with Apnea in Hospitalized Infants with Acute Respiratory Infection.

Apnea is a potentially life-threatening complication of severe acute respiratory infection (SARI) in early infancy; however, its determinants remain incompletely understood. Between 2011 and 2013, we conducted a population-based, cross-sectional, multicenter study in Buenos Aires, Argentina. We examined epidemiological, clinical, virological, and immunological factors associated with apnea in a population-based cohort of 2376 infants younger than five months hospitalized due to SARI. Using hierarchical multivariable logistic regression, we identified preterm birth, cesarean section, previous NICU admission, age under two months, and severe household crowding as independent predictors of apnea. RSV infection was inversely associated with apnea, and IL-5 levels in respiratory secretions were significantly lower among infants with apnea, suggesting a qualitatively different immune response in this group. Taken together, these findings indicate that apnea during SARI in early infancy is primarily driven by biological immaturity and adverse environmental conditions.