BACKGROUND AND PURPOSE:Vitamin D deficiency is a recognized risk factor for multiple sclerosis (MS) and is associated with increased disease activity. It has also been proposed that the lower the vitamin D levels are, the higher is the handicap.METHODS:To refine the links between vitamin D insufficiency and disability in MS patients, a retrospective cohort analysis was performed including 181 patients prospectively followed without previous vitamin D supplementation, and age, gender, age at MS onset, MS type, MS activity, Expanded Disability Status Scale (EDSS) were analysed in correlation with plasma vitamin D levels.RESULTS:Vitamin D levels were significantly higher in relapsing-remitting MS than in progressive forms of MS in multivariate analyses adjusted for age, ethnicity, gender, disease duration and season (P = 0.0487). Overall, there was a negative correlation between vitamin D level and EDSS score (P = 0.0001, r = -0.33). In relapsing-remitting MS, vitamin D levels were only correlated with disability scores for EDSS < 4 (P = 0.0012). Patients with >20 ng/ml of vitamin D were 2.78 times more likely to have an EDSS < 4 (P = 0.0011, 95% confidence interval 1.49-5.00).CONCLUSION:Data support previous work suggesting that vitamin D deficiency is associated with higher risk of disability in MS. Vitamin D levels also correlated with the degree of disability in fully ambulatory patients with relapsing-remitting MS. These additional results support the pertinence of randomized controlled trials analysing the interest of an early vitamin D supplementation in MS patients to influence evolution of disability.