Dose-response relationship between weight status and clinical outcomes in pediatric influenza-related respiratory infections.

Abstract

Associations between underweight/obesity and manifestations of influenza infection remain unclear, especially in children. This study investigated the dose-response relationships between weight status and clinical outcomes among children hospitalized with influenza-related respiratory infections. We obtained hospital discharge records of inpatients aged under 18 years with diagnoses of bronchitis/pneumonia and influenza, using a Japanese national inpatient database. The patients were classified as underweight, normal-weight, overweight, or obese groups using weight-for-length, weight-for-height, and body-mass-index for age following World Health Organization criteria. We compared need for intensive care, 30-day readmission, mean total hospitalization costs, and length of hospital stay across the four groups using multivariable regression models and restricted cubic spline functions. Overall, 27 771 patients were identified, including 2637 underweight, 19 701 normal-weight, 2675 overweight, and 2758 obese patients. The underweight group showed a significantly higher 30-day readmission (adjusted odds ratio, 1.68; 95% confidence interval, 1.28-2.18) and a longer length of stay (adjusted difference, 0.23 days; 95% confidence interval, 0.12-0.23 days) than the normal-weight group did. No significant differences in the need for intensive care or hospitalization costs were observed across the four weight status groups. The threshold for a statistically significant association between weight status and 30-day readmission was a z-score for weight-for-length, weight-for-height, or BMI for age of -0.95 (17th percentile). These findings demonstrated that underweight status is a risk factor for repeated hospital admissions because of influenza-related respiratory infections in children.