Interdependence and contributions of sun exposure and vitamin D to MRI measures in multiple sclerosis
- Robert Zivadinov1,
- Cierra N Treu2,
- Bianca Weinstock-Guttman3,
- Caitlin Turner2,
- Niels Bergsland1,
- Kerri O'Connor2,
- Michael G Dwyer1,
- Ellen Carl1,
- Deepa P Ramasamy1,
- Jun Qu2,
- Murali Ramanathan2,3
- 1Department of Neurology, Buffalo Neuroimaging Analysis Center, State University of New York, Buffalo, New York, USA
- 2Department of Pharmaceutical Sciences, State University of New York, Buffalo, New York, USA
- 3Department of Neurology, Multiple Sclerosis Center, State University of New York, Buffalo, New York, USA
- Correspondence to Professor M Ramanathan, Department of Pharmaceutical Sciences, State University of New York, Buffalo, 355 Kapoor Hall, Buffalo, NY 14214-8033, USA;
- Received 24 November 2012
- Revised 3 January 2013
- Accepted 10 January 2013
- Published Online First 5 February 2013
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 rp=0.29, p<0.001), BMI (rp=−0.24, p=0.001), summer sun exposure (rp=0.22, p=0.002) and darker eye colour (rp=−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, rp=0.16, p=0.019) and whole brain volume (WBV, rp=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 (rp=0.18, p=0.003) and GMV (rp=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.