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Sunlight is associated with decreased multiple sclerosis risk: no interaction with human leukocyte antigen‐DRB1*15
Author(s) -
Bäärnhielm M.,
Hedström A. K.,
Kockum I.,
Sundqvist E.,
Gustafsson S. A.,
Hillert J.,
Olsson T.,
Alfredsson L.
Publication year - 2012
Publication title -
european journal of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 124
eISSN - 1468-1331
pISSN - 1351-5101
DOI - 10.1111/j.1468-1331.2011.03650.x
Subject(s) - medicine , multiple sclerosis , vitamin d and neurology , odds ratio , confidence interval , sunlight , population , sun exposure , case control study , logistic regression , human leukocyte antigen , vitamin , immunology , physiology , environmental health , antigen , dermatology , physics , astronomy
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.