Effect of vitamin D on MS activity by disease-modifying therapy class

OBJECTIVE: To determine whether vitamin D status predicts disease activity in patients with multiple sclerosis (MS) taking interferon-β (IFN), glatiramer acetate (GA), and fingolimod (FTY). METHODS: Participants (n = 324) with relapsing-remitting MS on IFN (96), GA (151), or FTY (77) were identified from the Comprehensive Longitudinal Investigation of MS at Brigham and Women's Hospital (CLIMB) Study at the Partners MS Center. FTY-treated participants were analyzed separately because of differences in selection. Serum vitamin 25(OH)D concentration was adjusted for season. We evaluated the relationship between 25(OH)D tertile and time to relapse or gadolinium-enhancing lesion using a Cox model adjusted for age, sex, and disease duration. RESULTS: Higher 25(OH)D was associated with longer time to the combined endpoint in the overall IFN/GA cohort (p for trend = 0.042; hazard ratio [HR] = 0.77) and in the IFN subgroup (HR(IFN) = 0.58; p(IFN) = 0.012), but not in GA-treated participants (p = 0.50; HR = 0.89). For gadolinium-enhancing lesions alone, there was a significant association observed in GA and IFN subgroups, although the effect was more pronounced on IFN (HR(GA) = 0.57; p(GA) = 0.039 vs HR(IFN) = 0.41; p(IFN) = 0.022). No significant associations were found for relapses. For FTY, higher 25(OH)D was associated with longer survival for the combined endpoint (HR(FTY) = 0.48; p(FTY) = 0.016) and for relapses (HR(FTY) = 0.50; p(FTY) = 0.046), but not for gadolinium-enhancing lesions. CONCLUSIONS: Disease activity generally improved with higher 25(OH)D, but this study raises the question of effect modification by treatment class.