Children with epilepsy and intellectual disability have an increased risk of vitamin D deficiency. In this patient group, it is neither clear which factors are associated with the level of 25-hydroxyvitamin D nor what the therapeutic results are when Dutch guidelines are followed.

This retrospective study included 30 patients who, in October 2012, were residents of the children's wards of a tertiary epilepsy center in The Netherlands (Kempenhaeghe). From November 2012 onward they received cholecalciferol supplementation in doses that met or exceeded Dutch guidelines. At baseline, after 6, and 15 months, serum 25-hydroxyvitamin D concentration was measured.

At baseline, the vitamin D status in 11 (36.7%) residents was found to be deficient, in 10 (33.3%) to be insufficient and in 9 (30.0%) sufficient. Supplementation dose, diet, body mass index, intellectual disability, and mobility were significantly associated with baseline 25-hydroxyvitamin D concentrations. The mean 25-hydroxyvitamin D concentration increased significantly from 57.40 ± 22.00 nmol/L at baseline to 89.47 ± 26.77 nmol/L after 15 months (P < 0.001). In spite of supplementation ranging from 400 to 1200 IU/day, 64% of the residents in the deficient category and 30% of those with an insufficient level at baseline failed to attain a sufficient vitamin D status after 15 months.

Not all residents reached a sufficient vitamin D status after supplementation at least equal to the amount recommended by the Dutch guidelines. In a high-risk population, such as our residents, we advise monitoring 25-hydroxyvitamin D concentrations, adjusting supplementation accordingly and following patients to ensure they reach sufficiency.