Lack of association between vitamin D levels and bone mineral density in patients with multiple sclerosis

Background: There is conflicting evidence regarding the association of vitamin D status with bone mineral density (BMD) in adult patients with multiple sclerosis (MS). We evaluated cross-sectionaly the determinants (including vitamin D levels) of low BMD in patients with relapsing-remitting MS (RRMS).

Methods: The BMD at lumbar level (L2-L4) and femoral neck was measured in consecutive adult, ambulatory, RRMS patients by dual-energy X-ray absorptiometry. Blood samples were collected for total serum calcium, phosphorus, magnesium, 25-hydroxyvitamin D(3) and parathormone. Osteopenia and osteoporosis were defined according to the World Health Organization operational BMD definition. MS severity was assessed using the EDSS-score. Cross-sectional associations were evaluated using Spearman's correlation-coefficient and multiple linear regression models.

Results: A total of 119 patients were evaluated (mean age 39.2 ± 10.4 years; 40% men). Osteopenia at lumbar spine (L2-L4) and femoral neck was present in 26% (95%CI: 18%-35%) and 50% (95%CI: 41%-60%) of the patients respectively. Osteoporosis was documented at lumbar spine and femoral neck of 3% (95%CI: 0%-8%) and 11% (95%CI: 6%-18%) of the study population respectively. There was no correlation (p>0.1) of 25-hydroxyvitamin D3 levels with any of BMD measurements (including Z- and T-scores) both in lumbar spine and in femoral neck. Increasing MS duration and increasing dosage of intravenous corticosteroids were independently and negatively associated with both lumbar spine and femoral neck BMD.

Conclusions: We documented no correlation between vitamin D levels and decreased BMD at femoral neck and lumbar spine in RRMS patients. Vitamin D insufficiency appears not to be the underlying cause of secondary osteoporosis in MS.