25-hydroxyvitamin D levels are associated with multiple sclerosis in Iran: A cross-sectional study.

Vitamin D is being increasingly studied in multiple sclerosis (MS). A number of studies have shown that MS patients have lower levels of 25-hydroxyvitamin D as compared to comparator populations, but previous studies in Iran have been conflicting, perhaps due to their small sample size. We performed the largest study to date investigating 25-hydroxyvitamin D levels in Iranian MS patients (n=700) and controls (n=1000). 25-hydroxyvitamin D was measured using a quantitative chemiluminescent immunometric assay. 25-hydroxyvitamin D levels were lower in patients with MS. Over 24% of controls were vitamin D sufficient as compared to 3.4% of patients. Logistic regression showed that for every 1 ng/mL increase in 25-hydroxyvitamin D, the odds for MS decreased (odds ratio=0.87; 95% confidence interval (CI) 0.85-0.88; p<0.001), after adjusting for age and sex. There was no association between 25-hydroxyvitamin D levels and disability scores in MS patients. Iranian Patients with MS have low levels of vitamin D and, where deemed necessary, appropriate supplementation should be given.