Serum vitamin D concentrations and associated severity of acute lower respiratory tract infections in Japanese hospitalized children

Background: Vitamin D is an immunomodulatory molecule related to innate immunity that may contribute to the increased occurrence of acute lower respiratory infection (ALRI) in children, one of the most common reasons for hospitalization and intensive care unit admission. In the present study, the association between vitamin D deficiency and the severity of respiratory infection was evaluated by determining serum concentrations of 25‐hydroxyvitamin D (25(OH)D) in a group of hospitalized children with ALRI. Methods: Of the 28 children admitted to Nihon University Nerima‐Hikarigaoka Hospital with ALRI over the period November 2008–May 2009, 26 were diagnosed as having bronchiolitis and two were found to have pneumonia. A competitive protein binding radioimmunoassay was used to determine serum 25(OH)D concentrations. Results: Mean 25(OH)D concentrations in breast‐fed children with ALRI (n = 7) were significantly lower than those in children with ALRI who were bottle fed/weaned (n = 6) or on a regular diet (n = 15; 14.6 ± 9.7, 28.9 ± 6.9 and 24.6 ± 8.8 ng/mL, respectively). There was a significant correlation between vitamin D deficiency (