Interferon-β and serum 25-hydroxyvitamin D interact to modulate relapse risk in MS

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 p = 0.82). 25(OH)D was associated with a reduced relapse risk only among persons on IFN-β ( p 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.