Background and Aim: Observational studies have demonstrated that the risk of developing multiple sclerosis (MS) is associated with vitamin D (25(OH)D) status. However, there is no local study regarding vitamin D status in MS patients in the South Khorasan. Therefore, present study aimed at comparing the serum levels of vitamin D between the South Khorasan MS patients and healthy subjects, and determining its association with disability in these patients.

Materials and Methods: In this case-control study a total of 144 individuals (72 previously diagnosed MS cases and 72 age and sex matched healthy controls) were included. Demographic characteristics and serum vitamin D levels of both groups as well as Expanded Disability Status Scale (EDSS) for MS patients were assessed. The obtained data was analyzed using t-test, Mann Whitney U test, Chi-square, and Pearson's correlation coefficient test applying SPSS software.

Results: There was a significant difference (P<0.0001) in vitamin D levels between the case (47.4±5.4ng/mL) and the control (14.66±10.4 ng/mL) groups. A direct association was found between vitamin D levels and EDSS in MS patients (P<0.0001), too.

Conclusion: Surprisingly, it was found that vitamin D level was significantly higher in MS patients than the controls. There was a significant positive association between the level of vitamin D and disability status in patients with MS. The association may be due to more administration of vitamin D supplement to MS patients.