Longitudinal change of vitamin D status in children with epilepsy on antiepileptic drugs: prevalence and risk factors.

Background: Our aim was to evaluate the prevalence and risk factors of vitamin D deficiency and the changes of vitamin D level among children with epilepsy on antiepileptic drugs.

Methods: The levels of serum 25-hydroxy vitamin D were measured at the start of antiepileptic drugs and at 6- to 12-month intervals in children with epilepsy taking antiepileptic drugs in Pusan National University Children's Hospital. Vitamin D deficiency was defined as 25-hydroxy vitamin D levels <20 ng/mL and insufficiency between 21 and 29 ng/mL.

Results: A total of 143 children (103 boys and 40 girls) with the mean age of 7.4 ± 5.4 years were included. The mean follow-up duration was 1.8 ± 0.8 years. At the start of antiepileptic drugs and the last follow-up, vitamin D deficiency or insufficiency was recognized in 56.6% (81 of 143) and 79.0% (113 of 143), respectively (P < 0.01). The mean value of initial 25-hydroxy vitamin D was 31.1 ± 14.7 ng/mL, which was significantly decreased to 20.2 ± 14.9 ng/mL (P < 0.01) in the last follow-up. Polytherapy (-16.0 ± 13.6 ng/mL), longer duration of ≥2 years (-23.5 ± 9.1 ng/mL), tube feeding (-18.2 ± 14.5 ng/mL), and overweight with body mass index of eighty-fifth percentile or greater (-17.0 ± 12.1 ng/mL) had a significant negative effect for the longitudinal change of 25-hydroxy vitamin D. Age, etiologies, seizure outcomes, and type of antiepileptic drugs (enzyme-inducing versus nonenzyme-inducing antiepileptic drugs) did not affect the longitudinal decrease of 25-hydroxy vitamin D.

Conclusions: A high proportion of these children on antiepileptic drugs had hypovitaminosis D and a significant decrease between the initial and the last follow-up. Polytherapy and longer duration of antiepileptic drugs, tube feeding, and overweight were independently associated with longitudinally significant decrease of 25-hydroxy vitamin D.