University of Bergen/Haukeland University Hospital
Department of Clinical Medicine

Author Of 1 Presentation

Epidemiology Poster Presentation

P0500 - The impact of seasonal fluctuations of vitamin D on long-term disability progression in MS (ID 1353)

Abstract

Background

Vitamin D is associated with inflammatory activity in MS, but it is less clear whether seasonal fluctuations of vitamin D levels can affect long-term prognosis in MS.

Objectives

We examined whether seasonal fluctuations of serum vitamin D levels were associated with long-term (10 years) disability scores in a well-defined group of adult Norwegian MS patients.

Methods

A cohort of 80 patients with relapsing-remitting MS completed a randomized controlled study on ω-3 fatty acids between 2004 and 2008. During the study period of 24 months, serum 25-hydroxyvitamin D (25[OH]D) were measured at 9 time points: at baseline, and then at month 1, 3, 6, 7, 9, 12, 18, and 24. A mean value per season (summer, fall, winter, spring) was calculated from these values. In 2017, a follow-up study was conducted, including disability assessment by the Expanded Disability Status Scale (EDSS). In linear regression models, we explored the association between dichotomized values of 25(OH)D (“above median” and “below median”) per season and the change in EDSS score 10 years later.

Results

The highest 25(OH)D levels were seen during summer (June-August: mean = 85.9 nmol/L, median = 81.0 nmol/L) when solar radiation peaks in Norway, and the lowest 25(OH)D levels were seen during spring (March-May: mean 55.8 nmol/L, median = 52.5 nmol/L). Higher 25(OH)D levels during winter, spring, and summer were significantly associated with less disability progression after 10 years in separate models adjusted for age, sex, and baseline EDSS score. However, in a model mutually adjusted for 25(OH)D levels for all four seasons, only spring levels remained significantly associated with disability progression. In this model, the EDSS change was 0.71 point (95% CI: 0.02 to 1.40) lower for patients with above compared to below median spring levels. The effect estimate remained similar after further adjusting for disease duration and disease-modifying treatment.

Conclusions

In our study population, low vitamin D levels during spring were significantly associated with greater long-term disability progression. This finding suggests that vitamin D supplements may be of extra importance during this season.

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