Interdependence and contributions of sun exposure and vitamin D to MRI measures in MS

Summary: This study from the US looked at the relationship of sun exposure history, supplementation and environmental factors to vitamin D levels in multiple sclerosis patients and evaluated the associations between sun exposure and MRI measures. 

264 MS patients underwent neurological and 3 T MRI examinations as well as blood tests to measure vitamin D metabolites using mass spectroscopy. Results showed that vitamin D supplementation, BMI, summer sun exposure and darker eye colour had the strongest associations with vitamin D metabolite levels in the MS group. 

Interestingly, summer sun exposure was associated with increased grey matter volume (GMV) and whole brain volume (WBV) after correcting for EDSS in the MS group. Inclusion of 25-hydroxy vitamin D3 levels did not substantially affect the positive associations of sun exposure with WBV and GMV in the MS group. Therefore, sun exposure may have direct effects on MRI measures of neurodegeneration in MS, independent of vitamin D.

Abstract

PURPOSE: To assess the relationships of sun exposure history, supplementation and environmental factors to vitamin D levels in multiple sclerosis (MS) patients and to evaluate the associations between sun exposure and MRI measures.

METHODS: This study included 264 MS patients (mean age 46.9±10 years, disease duration 14.6±10 years; 67.8% relapsing-remitting, 28% secondary progressive and 4.2% primary progressive MS) and 69 healthy controls. Subjects underwent neurological and 3 T MRI examinations, provided blood samples and answered questions to a structured questionnaire. Information on race, skin and eye colour, supplement use, body mass index (BMI) and sun exposure was obtained by questionnaire. The vitamin D metabolites (25-hydroxy vitamin D3, 1, 25-dihydroxy vitamin D3 and 24, 25-dihydroxy vitamin D3) were measured using mass spectrometry.

RESULTS: Multivitamin supplementation (partial correlation r(p)=0.29, p<0.001), BMI (r(p)=-0.24, p=0.001), summer sun exposure (r(p)=0.22, p=0.002) and darker eye colour (r(p)=-0.18, p=0.015) had the strongest associations with vitamin D metabolite levels in the MS group. Increased summer sun exposure was associated with increased grey matter volume (GMV, r(p)=0.16, p=0.019) and whole brain volume (WBV, r(p)=0.20, p=0.004) after correcting for Extended Disability Status Scale in the MS group. Inclusion of 25-hydroxy vitamin D3 levels did not substantially affect the positive associations of sun exposure with WBV (r(p)=0.18, p=0.003) and GMV (r(p)=0.14, p=0.026) in the MS group.

CONCLUSIONS: Sun exposure may have direct effects on MRI measures of neurodegeneration in MS, independently of vitamin D.

Authors: Zivadinov R, Treu CN, Weinstock-Guttman B

source: J NeurolNeurosurg Psychiatry. 2013 Feb 5 & Pubmed PMID: 23385850 (14/02/13)