Sunlight is associated with decreased multiple sclerosis risk: no interaction with human leukocyte antigen-DRB1*15
Article first published online: 31 JAN 2012
© 2012 The Author(s) European Journal of Neurology © 2012 EFNS
European Journal of Neurology
Volume 19, Issue 7, pages 955–962, July 2012
How to Cite
Bäärnhielm, M., Hedström, A. K., Kockum, I., Sundqvist, E., Gustafsson, S. A., Hillert, J., Olsson, T. and Alfredsson, L. (2012), Sunlight is associated with decreased multiple sclerosis risk: no interaction with human leukocyte antigen-DRB1*15. European Journal of Neurology, 19: 955–962. doi: 10.1111/j.1468-1331.2011.03650.x
- Issue published online: 13 JUN 2012
- Article first published online: 31 JAN 2012
- Received 4 October 2011 Accepted 9 December 2011
- 25-hydroxyvitamin D;
- case–control studies;
- multiple sclerosis;
Background: Both insufficient exposure to sunlight and vitamin D deficiency have been associated with an increased risk for multiple sclerosis (MS). An interaction between human leukocyte antigen HLA-DRB1*15 and vitamin D in MS was recently proposed. We investigated the association between previous exposure to ultraviolet radiation (UVR), vitamin D status at inclusion in the study, and MS risk including the interaction of these factors with HLA-DRB1*15.
Methods: A population-based case–control study involving 1013 incident cases of MS and 1194 controls was performed in Sweden during 2005–2010. Subjects were classified according to their UVR exposure habits, vitamin D status, and HLA genotypes. The associations between different sun exposure habits/vitamin D levels and MS were calculated as odds ratios (OR) with 95% confidence intervals (CI) using logistic regression. Potential interaction was evaluated by calculating the attributable proportion due to interaction.
Results: Subjects with low UVR exposure had a significantly increased risk of MS compared with those who reported the highest exposure (OR 2.2, 95% CI 1.5–3.3). Similarly, subjects who had 25-hydroxy-vitamin D levels less than 50 nM/l had an increased risk for MS (OR 1.4, 95% CI 1.2–1.7). The association between UVR exposure and MS risk persisted after adjustment for vitamin D status. There was no interaction with HLA-DRB1*15 carriage.
Conclusions: UVR and vitamin D seem to affect MS risk in adults independently of HLA-DRB1*15 status. UVR exposure may also exert a protective effect against developing MS via other pathways than those involving vitamin D.