Dose-dependent relationships between weight status and clinical outcomes among infants hospitalized with respiratory syncytial virus infections.

Abstract

Associations between weight status and manifestations of respiratory syncytial virus infections remain unclear, especially in infants. This study investigated the dose-response relationships between weight status and clinical outcomes among infants hospitalized with respiratory syncytial virus infections. We obtained hospital discharge records for inpatients aged <12 months with diagnoses of bronchitis/pneumonia and respiratory syncytial virus infections, using a Japanese national inpatient database. The patients were classified into underweight, normal-weight, or overweight/obese groups using weight-for-length according to World Health Organization criteria. We compared need for intensive care, 30-day readmission, mean total hospitalization costs, and length of hospital stay across the three groups using multivariable mixed-effects regression models and restricted cubic spline functions. Overall, 42 698 patients were identified, comprising 3697 underweight, 35 849 normal-weight, 3152 overweight/obese patients. The underweight group had significantly higher risk of intensive care (adjusted odds ratio, 1.35; 95% confidence interval, 1.18-1.82) and longer length of stay (adjusted difference, 0.12 days; 95% confidence interval, 0.04-0.20 days) than the normal-weight group. No significant differences in 30-day readmission or hospitalization costs were observed among the three groups. The lower and upper thresholds for a significant association between weight status and intensive care were weight-for-length z-scores of -0.64 (26th percentile) and 2.08 (98th percentile), respectively. These findings demonstrate that abnormal weight status is an independent risk factor for greater illness severity among infants hospitalized with respiratory syncytial virus infections.