Interaction between vitamin D level, antiseizure medications (ASM) and seizure control in epilepsy adult patients

To investigate vitamin D levels and factors associated with seizure control in adult patients with epilepsy (APE).

Cross-sectional study with APE in routine outpatient follow-up at a neurology clinic. Clinical variables, antiseizure medications (ASM) and vitamin D were investigated. Data were analyzed using the Chi² or Fisher's exact tests, Mann-Whitney, Spearman's correlation coefficient, ROC curve and univariate and multiple logistic regression analysis.

Mean age was 46.5±15.1 years and disease duration was 27.5±17.0 years; 52.7% (n=49) of patients used one ASM and 47.3% (n=44) used≥2 ASM. There was a significant difference in the level of vitamin D according to the number of ASM and it was higher in patients who used a single ASM (26.02±10.22 versus 22.50±8.69; P=0.048). In the logistic regression, when vitamin D level was set at 20ng/mL, the chance of seizure control for patients using a single ASM was 6.99 times greater than for those using≥2 ASM. When vitamin D level was set at 40ng/mL, the number of ASM did not modify seizure control. There was no correlation between vitamin D and disease duration, patient age and age at the time of the first seizure. In the logistic regression, it was observed that satisfactory levels of vitamin D did not modify potential seizure control.

Thirty-three percent (33%) of patients presented with vitamin D deficiency (values below 20ng/mL) and 80% had vitamin D levels below what is recommended (30ng/mL). The use of ASM, when associated with different levels of vitamin D, modified the probability of seizure control in APE. Vitamin D levels and intrinsic epilepsy factors are associated with failure to effectively control seizures.