PURPOSE OF THE STUDY.
To assess for an association between serum 25-hydroxyvitamin D (25-OHD) levels at birth and at 2 years of age and the development of allergic sensitization and disorders in early childhood.
Subjects were part of a randomized, double-blinded, placebo-controlled trial designed to evaluate the effect of probiotics on allergy development. Infants with family history of atopy (1 or both parents had doctor-diagnosed allergic disease) were managed from birth until 5 years of age (n = 819).
Subjects were examined at 3 months, 6 months, 2 years, and 5 years of age. The primary outcome was the cumulative incidence of any allergic disease and any immunoglobulin E (IgE)–mediated allergic disease until the age of 2 or 5 years. Skin prick tests and serum-specific IgE to a panel of foods and environmental aeroallergens were completed at 2 and 5 years. Sensitization was defined as at least 1 or more positive skin prick test (≥3 mm larger than negative control) results or positive serum-specific IgE (>0.7 kU/L) results. IgE-mediated allergy was defined as sensitization that matched the allergic disorder. 25-OHD levels were measured from cord blood at birth (divided into tertiles) and serum at 2 years of age (divided into quartiles). The following variables were included in the multivariate logistic regression if they met the criteria for confounding: sex, dual parental allergy, mode of delivery, season of birth, season when 2-year serum sample was drawn, months of exclusive breastfeeding, household smoking (at age 0–2 years), and having a cat or dog in the household (at age 0–2 years). Probiotic treatment group was included in all regression models.
Cord blood 25-OHD levels in the second tertile (21.5–29.5 nmol/L) were significantly associated with increased allergic sensitization by 2 years of age (odds ratio [OR] 1.59; 95% confidence interval [CI]: 1.06–2.39) and allergic disorders by 5 years (OR 1.85; 95% CI: 1.25–2.73). 25-OHD levels measured at 2 years of age in the third quartile (51.7–62.6 nmol/L) were significantly associated with increased allergic sensitization by 5 years (OR 2.23; 95% CI: 1.21–4.12), increased diagnosis of IgE-associated allergic disorder by 5 years (OR 2.35; 95% CI: 1.22–4.52), and increased IgE-associated eczema by 5 years (OR 2.06; 95% CI: 1.02–4.17). A change in 25-OHD levels between birth and 2 years was not associated with allergic outcomes.
Significantly increased odds of allergic sensitization and/or physician-diagnosed, IgE-mediated allergic disorder or eczema in early childhood were found at the following 25-OHD levels: 21.5 to 29.5 nmol/L from cord blood at birth and 51.7 to 62.6 nmol/L at 2 years of age. 25-OHD levels measured at birth and 2 years of age were nonlinearly associated with allergic sensitization and disease.
The authors of few studies have evaluated the effect of 25-OHD in early childhood through a prospective study by using measurements of vitamin D at 2 time points. Conflicting results have been published in the literature on the effect of 25-OHD on allergic outcomes. The authors of this study highlight that the relationship between vitamin D and allergy could be nonlinear and warrants further study.
- Copyright © 2017 by the American Academy of Pediatrics