The relationship between vitamin D levels and cognitive impairment in patients with multiple sclerosis.

OBJECTIVE Neurocognitive impairment is one of the most common manifestations of multiple sclerosis (MS). However, the pathophysiology of this issue is still poorly understood. The objective of this study is to investigate the relationship between vitamin D levels and cognitive function in patients with MS as assessed by the Cambridge Neuropsychological Test Automated Battery (CANTAB). PATIENTS AND METHODS This was a cross-sectional, case-control study; the subjects were 39 Saudi patients diagnosed with MS. For all participants, demographic information, including age, sex, and educational level, was collected. Participants were also evaluated using the disease steps scale and the PHQ-9 scale. Their vitamin D levels were assessed, and the participants completed a computerized cognitive assessment using the CANTAB. RESULTS From the total sample of 39 patients with MS, 31 (79.5%) were female. Physical disability due to MS was insignificant in 25 (64.1%) of the subjects and significant in 14 (35.9%). Seventeen (43.6%) of the participants had normal vitamin D levels; 22 (56.4%) had low vitamin D levels. The MS patients had lower MOT mean errors than the control group, and this difference was statistically significant (t = -4.313, p < 0.01). Moreover, the scores of the two groups for all subcategories of the memory domain were different at statistically significant levels. Furthermore, the control group had higher PAL total errors (adjusted), PAL total errors (6 shapes, adjusted), and PRM percent correct than the MS patients (p < 0.01). The control group also achieved lower scores on SWM between errors and SWM strategy than the MS patients (p < 0.01). The MOT mean error was found to correlate with the disease steps score (r = 0.394, p < 0.05) and with significant physical disability (r = 0.457, p< 0.01). In the memory domain, PAL total errors (adjusted) correlated with age (r = 0.381, p < 0.05), SWM between errors correlated with age at onset of disease (r = 0.345, p < 0.05), and vitamin D level (r = 0.335, p < 0.05) and SWM strategy correlated with the number of relapses in the past 12 months (r = -0.355, p < 0.05). CONCLUSIONS Cognitive performance was impaired in patients with MS. Vitamin D deficiency, a potentially modifiable risk factor, independently predicted cognitive impairment in MS patients.