Seasonal fluctuations in serum levels of vitamin D in Japanese patients with multiple sclerosis.

We explored the presence of seasonal fluctuations in serum vitamin D levels and potential relationship between vitamin D levels and disease severity or prognosis in patients with multiple sclerosis (MS) in northern Japan. Serum levels of 25(OH)D in spring were significantly lower than in summer and autumn, whereas no differences in 1,25(OH)2D levels were demonstrated among four seasons. Seasonal fluctuations in 25(OH)D were demonstrated in patients with EDSS ≤3.5, but not in those with EDSS≥4.0. Negative correlations between 25(OH)D and EDSS or MSSS were found in each season. Seasonal fluctuations in 25(OH)D levels may be affected by physical disabilities.