Associations of maternal and fetal 25‐hydroxyvitamin D levels with childhood lung function and asthma: the Generation R Study

T Gazibara, H T den Dekker, J C de Jongste, J J McGrath, D W Eyles, T H Burne, I K Reiss, O H Franco, H Tiemeier, V W V Jaddoe, L Duijts

Exposure to low levels of vitamin D in fetal life might be a risk factor for childhood asthma. We examined whether 25-hydroxyvitamin D levels in mid-gestation and at birth were associated with higher airway resistance and inflammation, and increased risks of wheezing and asthma in school-age children. We performed a population-based prospective cohort study among 3,130 mothers and their children. Maternal blood samples in mid-gestation and umbilical cord blood samples at birth were used to determine 25-hydroxy vitamin D levels. At age 6 years, airway resistance (Rint) was measured by interrupter technique and airway inflammation by Fractional exhaled Nitric Oxide (FENO) using NIOX chemiluminescence analyzer. Wheezing and asthma were prospectively assessed by annual questionnaires until age 6 years. Maternal levels of 25-hydroxy vitamin D in mid-gestation were not associated with Rint, FeNO, wheezing patterns or asthma. Children in thelowest tertile of 25-hydroxy vitamin D levels at birth had a higher Rint (Z-score (95% Confidence Interval[95% CI]): -0.42 (-0.84, -0.01), p-value for trend<0.05), compared to those in the highest tertile group. The effect estimate attenuated when child's current 25-hydroxy vitamin D level was taken into account (Z-score (95% CI): -0.55 (-1.08, 0.01)). Low levels of 25-hydroxy vitamin D at birth were associated with a higher airway resistance in childhood. Additional adjustment for child's current 25-hydroxy vitamin D level reduced the effect size of the association. Further studies are needed to replicate these findings and to examine mechanisms underlying the observed association, and the long-term consequences. This article is protected by copyright. All rights reserved.