biostudies-literatureUnknown333(16)Thouvenot E<h4>Importance</h4>Vitamin D deficiency is a risk factor for multiple sclerosis (MS) and is associated with the risk of disease activity, but data on the benefits of supplementation are conflicting.<h4>Objective</h4>To evaluate the efficacy of high-dose cholecalciferol as monotherapy in reducing disease activity in patients with clinically isolated syndrome (CIS) typical for MS.<h4>Design, setting, and participants</h4>The D-Lay MS trial was a parallel, double-blind, randomized placebo-controlled clinical trial in 36 MS centers in France. Patients were enrolled from July 2013 to December 2020 (final follow-up on January 18, 2023). Untreated patients with CIS aged 18 to 55 years with CIS duration less than 90 days, serum vitamin D concentration less than 100 nmol/L, and diagnostic magnetic JAMA1413-1422https://www.ebi.ac.uk/biostudies/studies/S-EPMC11894546biostudies-literatureHigh-Dose Vitamin D in Clinically Isolated Syndrome Typical of Multiple Sclerosis: The D-Lay MS Randomized Clinical Trial.PMC11894546Collongues NCastelnovo GLe Page ECamu WTaithe FHeinzlef ODevy RLejeune FDerache NMoreau TRival MCasez OGaillard NLaplaud DTourbah AVukusic SBiotti DWiertlewski SCiron JThouvenot EGalanaud DAyrignac XPapeix CPatry IGuennoc AMMaillart ESchunck ARenard DDeburghgraeve VDubessy Anne LClavelou PMichel LUngureanu AHautecoeur PCalais GAufauvre DTalmant VMagy LEdan GDelalande LFaighel MMas JMontcuquet ALancin Garcia CFroment-Tilikete CBrassat DDe Seze JBenoilid ADurand-Dubief FKerbat AOutteryck OBourre BDemattei CD-Lay MS InvestigatorsMura TMaarouf AYeung JNifle CLouapre CCohen MBiberon JLebrun-Frenay CFromont AGout OAgherbi HPittion-Vouyovitch SCouloume LDeschamps RCarra Dalliere CWacongne AVaillant MCoustans MCaucheteux NFabbro-Peray PfalseHigh-Dose Vitamin D in Clinically Isolated Syndrome Typical of Multiple Sclerosis: The D-Lay MS Randomized Clinical Trial.<h4>Importance</h4>Vitamin D deficiency is a risk factor for multiple sclerosis (MS) and is associated with the risk of disease activity, but data on the benefits of supplementation are conflicting.<h4>Objective</h4>To evaluate the efficacy of high-dose cholecalciferol as monotherapy in reducing disease activity in patients with clinically isolated syndrome (CIS) typical for MS.<h4>Design, setting, and participants</h4>The D-Lay MS trial was a parallel, double-blind, randomized placebo-controlled clinical trial in 36 MS centers in France. Patients were enrolled from July 2013 to December 2020 (final follow-up on January 18, 2023). Untreated patients with CIS aged 18 to 55 years with CIS duration less than 90 days, serum vitamin D concentration less than 100 nmol/L, and diagnostic magnetic 2025-01-01T00:00:00Z2025 Apr2026-06-02T17:45:46.586Z2026-05-27T03:07:42.928ZS-EPMC118945464006304110.1001/jama.2025.1604