Relationship between 25-OH-D serum level and relapse rate in multiple sclerosis patients before and after vitamin D supplementation.

Background:Vitamin D could play a protective role in multiple sclerosis.Methods:In an observational, uncontrolled study, vitamin D3 supplementation (3010 IU/day on average) was given to 156 consecutive patients with relapsing–remitting multiple sclerosis, under first-line immunomodulatory therapy and with initial 25-OH-D serum level lower than 100 nmol/l (40 ng/ml). Relapses were determined for 29.1 ± 8.4 months during vitamin D and 29.8 ± 10.1 months before supplementation. The 25-OH-D level was measured before supplementation and several times during supplementation. The incidence rate of relapses before and during supplementation was estimated using negative binomial regressionmodels with follow-up durations as offset terms. The incidence rate and incidence rate ratioof relapses at various 25-OH-D levels were also calculated using negative binomial regressionmodels.Results:In 76 patients, immunomodulatory therapy preceded vitamin D supplementation (by 4.2 ± 2.7 years) and in 80 patients both treatme...