Nationwide Study of Respiratory-Related Hospitalisations and Deaths in Preterm Children in Brazil: A Registry-based Study

Background: Preterm birth and respiratory diseases disproportionately affect low-and middle-income countries (LMICs). Although preterm birth is a major contributor to the burden of respiratory morbimortality in early childhood, most evidence comes from high-income settings. To address this gap, we examined respiratory-related hospitalisations and deaths among preterm children in Brazil. Methods: We conducted a population-based cohort study using the CIDACS Birth Cohort, including all live births in Brazil from January 1, 2011, to November 30, 2018. Preterm infants were defined as infants born before 37 weeks of gestation. We examined respiratory-related hospital admissions and deaths in children under five. Mean ratios (MR) and 95% confidence intervals (CI) were estimated using the Ghosh-Lin model; hazard ratios (HR) were estimated using Cox models. Maternal characteristics were adjusted through inverse probability weighting, with treatment probabilities estimated via entropy balancing. Results: The study included 3,239,563 live births, with 288,466 (8.9%) classified as preterm. The MR for under-five respiratory hospitalisation, comparing preterm to term births, was 1.40 (95%CI:1.38–1.42), peaking at 1.68 (1.63–1.72) between 28 and 90 days, declining to approximately 1.18 (1.10-1.28) at the fourth year. For respiratory disease deaths, the under-five HR was 3.94 (3.62–4.30). Respiratory-related mortality was highest between 28-90 days of age, with an HR of 4.66 (4.00–5.43), decreasing to 1.25 (0.62–2.51) by three years of age. Conclusion: Preterm newborns have a higher risk of respiratory illness than full-term children, particularly in their first year. This understanding can guide health strategies to address premature birth issues by identifying important periods of vulnerability.