Factors Associated with Acute Lower Respiratory Infections in Children Under Five at a Peruvian Emergency Hospital.

Background/Objectives: Acute lower respiratory infections (ALRIs) are an important cause of morbidity among children under five years of age. This study aimed to identify factors associated with ALRI among children under five treated at a Peruvian emergency hospital. Methods: We conducted an observational, analytical, retrospective cross-sectional study using medical records of children treated in the pediatric emergency department of Hospital de Emergencias José Casimiro Ulloa, Lima, Peru, between January and December 2024. ALRI was defined as a physician-recorded diagnosis of pneumonia or bronchiolitis; the comparison group comprised children with acute bronchitis or upper respiratory tract infection. Crude and adjusted prevalence ratios (PRs) with 95% confidence intervals (CIs) were estimated using Poisson regression with robust variance. Results: The final sample included 322 children, of whom 154 (47.8%) had ALRI. In the adjusted model, age 0 to <2 years (aPR = 1.27; 95% CI: 1.03-1.56), absence of exclusive breastfeeding (aPR = 1.24; 95% CI: 1.02-1.51), birth weight < 1000 g (aPR = 1.43; 95% CI: 1.09-1.87), incomplete immunizations (aPR = 1.28; 95% CI: 1.07-1.53), and passive smoking exposure (aPR = 1.38; 95% CI: 1.15-1.65) were independently associated with higher ALRI prevalence. Conclusions: ALRI accounted for nearly half of the ARI diagnoses in this pediatric emergency analytical sample. Younger age, absence of exclusive breastfeeding, extremely low birth weight, incomplete immunizations, and passive smoking exposure were independently associated with ALRI and may help identify children requiring closer clinical assessment and preventive interventions.