Association of vitamin D supplementation with respiratory tract infection in infants

Abstract

Vitamin D deficiency has been reported to be associated with respiratory tract infection (RTI). However, evidence regarding the effects of vitamin D supplementation on susceptibility of infants to RTI is limited. In this prospective birth cohort study, we examined whether vitamin D supplementation reduced RTI risk in 2,244 infants completing the follow-up from birth to 6 months of age. The outcome endpoint was the first episode of paediatrician-diagnosed RTI or 6 months of age when no RTI event occurred. Infants receiving vitamin D supplements at a daily dose of 400–600 IU from birth to the outcome endpoint were defined as vitamin D supplementation and divided into four groups according to the average frequency of supplementation: 0, 1–2, 3–4, and 5–7 days/week. We evaluated the relationship between vitamin D supplementation and time to the first episode of RTI with Kaplan–Meier plots. The associations of vitamin D supplementation with infant RTI, lower RTI (LRTI), and RTI-related hospitalization were assessed using modified Poisson regression. The median time to first RTI episode was 60 days after birth (95% CI [60, 90]) for infants without supplementation and longer than 6 months of age for infants with supplementation (p