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Abstract
Objective: To determine whether interferon-β (IFN-β) medication use is associated with vitamin D levels and whether the two interact in exerting effects on relapse risk.
Methods: In a prospective cohort of 178 persons with clinically definite multiple sclerosis (MS) living in southern Tasmania in 2002–2005, serum 25-hydroxyvitamin D [25(OH)D] was measured biannually, with assessment by questionnaire for relevant factors, including IFN-β treatment.
Results: Subjects reporting IFN-β use had significantly higher mean 25(OH)D than persons who did not (p < 0.001). This was mediated by an interaction between personal sun exposure and IFN-β, with treated persons realizing nearly three times 25(OH)D per hour of sun exposure of persons not on therapy. The association between 25(OH)D and 1,25-dihydroxyvitamin D did not differ by IFN-β therapy (p = 0.82). 25(OH)D was associated with a reduced relapse risk only among persons on IFN-β (p < 0.001). Importantly, IFN-β was only protective against relapse among persons with higher 25(OH)D (hazard ratio [HR] 0.58 [95% confidence interval (CI) 0.35–0.98]), while among 25(OH)D-insufficient persons, IFN-β increased relapse risk (HR 2.01 [95% CI 1.22–3.32]).
Conclusion: In this study, we found that IFN-β therapy is associated with greater production of vitamin D from sun exposure, suggesting part of the therapeutic effects of IFN-β on relapse in MS may be through modulation of vitamin D metabolism. These findings suggest persons being treated with IFN-β should have vitamin D status monitored and maintained in the sufficiency range.
Classification of evidence: This study provided Class III evidence that IFN-β is associated with reduced risk of relapse, and this effect may be modified by a positive effect of IFN-β on serum 25(OH)D levels.
GLOSSARY
- 25(OH)D=
- 25-hydroxyvitamin D;
- 7-DHC=
- 7-dehydrocholesterol;
- BMI=
- body mass index;
- CI=
- confidence interval;
- EDSS=
- Expanded Disability Status Scale;
- HR=
- hazard ratio;
- IFN-β=
- interferon-β;
- MS=
- multiple sclerosis;
- RRMS=
- relapsing-remitting multiple sclerosis
Footnotes
↵* These authors contributed equally to this work.
Study funding: The MS Longitudinal Study was funded by a grant from the Australian National Health & Medical Research Council (Project 211308). Additional funding for 25(OH)D measures provided by the Trish Foundation. Additional funding for 1,25(OH)2D measures provided by a University of Tasmania Rising Star Award. I.v.d.M. is supported by a Future Fellowship from the Australian Research Council.
Editorial, page 208
Supplemental data at www.neurology.org
- Received August 21, 2011.
- Accepted November 14, 2011.
- Copyright © 2012 by AAN Enterprises, Inc.
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