Serum 25-hydroxyvitamin D levels in multiple sclerosis patients from the north of Portugal.

Increasing evidence has shown that individuals with Multiple Sclerosis (MS) have lower 25-hydroxyvitamin D [25(OH)D] levels compared to healthy controls. There is no information regarding 25(OH)D levels and MS in Portugal. Therefore the aim of the current study was to examine the levels of 25(OH)D in a group of patients with MS and in healthy matched controls, as well as the association of 25(OH)D levels with disease course, disability and severity. A group of 244 unrelated Portuguese patients, with a definitive diagnosis of MS, and 198 ethnically matched healthy controls were included in the study. A sub-group of patients with recent disease onset was included. Serum 25(OH)D was measured using an electrochemiluminescence binding assay. The mean serum level of 25(OH)D in patients with MS was 39.9±22.0 nmol/L, which was significantly lower (p<0.0001) than those in healthy controls, 55.4±23.4 nmol/L. There was a negative correlation between 25(OH)D levels and EDSS (r=-0.293, p<0.0001) and MSSS scores (r=-0.293, p<0.0001). In multiple logistic regression analysis adjusted for age, gender, disease form, EDSS, disease duration and MSSS, 25(OH)D levels were independently associated with EDSS (p=0.004) and disease duration (p=0.016), and with MSSS (p=0.001). In accordance with the majority of the literature, low serum 25(OH)D levels were associated with susceptibility and disability in MS patients from Portugal. Lower serum 25(OH)D levels were also found in patients with a recent disease onset, supporting vitamin D levels as a risk factor for MS.