Background: low vitamin D status in pregnancy can influence the offspring's lung function and contribute to childhood asthma development. The objective of this study was to examine the influence of neonatal vitamin D status on the development of asthma among children age 3-9 years in a large population sample.
Method: in a case-cohort study utilizing a Danish biobank and register data we examined the association between neonatal 25-hydroxyvitamin D3 (25(OH)D3) concentrations and incidence of asthma among children aged 3-9 years. Cases of asthma (n = 911) were randomly selected among all cases of asthma in the Danish National Patient Register from children born between 1992 and 2002. The sub-cohort (n = 1423) was randomly selected among all children born in the same period. We used a weighted Cox proportional hazard model assessing the hazard of first asthma diagnoses by quintiles of 25(OH)D3.
Results: the median 25(OH)D3 (interquartile range) for asthma cases was 23 nmol/L (14-35) and the sub-cohort 25 nmol/L (14-40). The hazard ratio for developing asthma between ages 3 and 9 years was lower for children in the fifth quintile of neonatal 25(OH)D3 compared to children in the first quintile, both in the unadjusted (0.61 95% CI: 0.46-0.80) and adjusted (0.55 95% CI: 0.39-0.77) analyses.
Conclusion: the results from our study suggest that higher neonatal vitamin D concentration may reduce the risk of developing childhood asthma at ages 3-9 years, indicating that neonatal vitamin D status as a proxy of vitamin D status during the prenatal period is important for normal immune- and lung development.
Keywords: asthma; childhood; neonatal; vitamin D.