Association of serum 25-hydroxyvitamin D3 and D2 with academic performance in childhood: findings from a prospective birth cohort

Background Higher total serum 25-hydroxyvitamin D (25(OH)D) concentrations have been associated with better cognitive function mainly in cross-sectional studies in adults. It is unknown if the associations of different forms of 25(OH)D (25(OH)D-3 and 25(OH)D-2) are similar. Methods Prospective cohort study (n = 3171) with serum 25(OH)D-3 and 25(OH)D-2 concentrations measured at mean age of 9.8 years and academic performance at age 13-14 years (total scores in English, mathematics and science) and 15-16 years (performance in General Certificates of Education examinations). Results Serum 25(OH)D-3 concentrations were not associated with any educational outcomes. Higher 25(OH)D-2 concentrations were associated with worse performance in English at age 13-14 years (adjusted SD change per doubling in 25(OH)D-2 (95% CI) - 0.05 (-0.08 to -0.01)) and with worse academic performance at age 15-16 years (adjusted OR for obtaining >= 5 A*-C grades (95% CI) 0.91 (0.82 to 1.00)). Conclusion The null findings with 25(OH)D-3 are in line with two previous cross-sectional studies in children. It is possible that the positive association of 25(OH)D with cognitive function seen in adults does not emerge until later in life or that the results from previous cross-sectional adult studies are due to reverse causality. The unexpected inverse association of 25(OH)D-2 with academic performance requires replication in further studies. Taken together, our findings do not support suggestions that children should have controlled exposure to sunlight, or vitamin D supplements, in order to increase academic performance.