Cord blood vitamin D and neurocognitive development are nonlinearly related in toddlers

Background Little is known about the relation between vitamin D status in early life and neurodevelopment outcomes. Objective This study was designed to examine the association of cord blood 25-hydroxyvitamin D [25(OH)D] at birth with neurocognitive development in toddlers. Methods As part of the China-Anhui Birth Cohort Study, 363 mother-infant pairs with completed data were selected. Concentrations of 25(OH)D in cord blood were measured by radioimmunoassay. Mental development index (MDI) and psychomotor development index (PDI) in toddlers were assessed at age 16–18 mo by using the Bayley Scales of Infant Development. The data on maternal sociodemographic characteristics and other confounding factors were also prospectively collected. Results Toddlers in the lowest quintile of cord blood 25(OH)D exhibited a deficit of 7.60 (95% CI: −12.4, −2.82; P = 0.002) and 8.04 (95% CI: −12.9, −3.11; P = 0.001) points in the MDI and PDI scores, respectively, compared with the reference category. Unexpectedly, toddlers in the highest quintile of cord blood 25(OH)D also had a significant deficit of 12.3 (95% CI: −17.9, −6.67; P < 0.001) points in PDI scores compared with the reference category. Conclusions This prospective study suggested that there was an inverted-U–shaped relation between neonatal vitamin D status and neurocognitive development in toddlers. Additional studies on the optimal 25(OH)D concentrations in early life are needed.