Vitamin D has been considered an environmental factor in multiple sclerosis (MS) development. The prevalence of MS is high in North American and European countries in which the ultraviolet (UV) exposure in low. The UV is responsible for the synthesis of vitamin D in the skin. Some studies have shown that the serum vitamin D levels can fluctuate being these levels lower in winter than in summer. Moreover, low serum levels of vitamin D have been associated with worst disability in MS patients. However, the role of vitamin D is still unknown in MS patients from Ecuador, an Andean country with 12 months of solar exposure.
Our study seeks to establish the serum levels of vitamin D in Ecuadorian patients with MS and its influence on disability.
This is a retrospective study in which we measured the serum levels of vitamin D in MS patients who were attended at Carlos Andrade Marin Hospital in Quito, Ecuador. The severity of the disease was measured using the expanded disability status scale (EDSS). The Shapiro-Wilk test was used to determine if the distribution of the paired data was normal. The Wilcoxon signed-rank test was used to compare the paired data of the non-normal distribution. All the data were analyzed through SPSS version 25 and a value of p <0.05 was considered significant.
We included 66 patients with MS. The majority were female (69%). The mean age at the onset of the disease was 29.6 years (SD+/-11.7).The mean EDSS in the last follow up was 2.9 (range 0 – 8). The mean serum concentrations of vitamin D was 26.2 ng/ml (SD+/- 1.6). In this study, the prevalence of vitamin D hypovitaminosis was 81.8%. The prevalence of vitamin D deficiency (10-20 ng/mL), vitamin D insufficiency (20-30 ng/mL), and vitamin D sufficiency (>30 ng/mL) was 34.5%, 47.3%, and 18.2%, respectively. We found an inverse correlation between disability and serum levels of vitamin D (-0.24) but, the correlation was not statistically significant (p>0.5). The mean EDSS in those patients with serum vitamin D levels more than 30 ng/ml and less than 30 ng/ml was 2.6 SD+/-1.5 vs 3.1 SD+/-1.9 respectively, p=0.054.
We found a high prevalence of vitamin D hypovitaminosis in Ecuadorian patients with MS. The serum levels of vitamin D were not associated with disability. The main limitation of this study is its retrospective nature and the absence of control group. It is necessary more studies on the influence of vitamin D in Ecuadorian patients with MS.