Impaired ambulation and steroid therapy impact negatively on bone health in multiple sclerosis

BACKGROUND AND PURPOSE: The prevalence of osteopenia and osteoporosis is higher amongst patients with multiple sclerosis in comparison with the general population. In addition to the general determinants of bone health, two factors may contribute to reduced bone mineral density in multiple sclerosis: physical disability and corticosteroid therapy. The aim of this study was to examine the effect of physical disability and steroid exposure on bone health in weight-bearing bones and spine and on the incidence of low-trauma fractures in multiple sclerosis. METHODS: In this retrospective analysis of prospectively collected data, associations between bone mineral density (at the femoral neck, total femur and the lumbar spine) and its change with disability or cumulative steroid dose were evaluated with random-effect models adjusted for demographic and clinical determinants of bone health. The incidence of low-trauma fractures during the study follow-up was evaluated with Andersen-Gill models. RESULTS: Overall, 474 and 438 patients were included in cross-sectional and longitudinal analyses (follow-up 2347 patient-years), respectively. The effect of severely impaired gait was more apparent in weight-bearing bones (P ≤ 10(-15) ) than in spine (P = 0.007). The effect of cumulative steroid dose was relatively less pronounced but diffuse (P ≤ 10(-4) ). Risk of low-trauma fractures was associated with disability (P = 0.02) but not with cumulative steroid exposure and was greater amongst patients with severely impaired gait (annual risk 3.5% vs. 3.0%). Synergistic effects were found only between cumulative steroid dose in patients ambulatory without support (P = 0.02). CONCLUSIONS: Bone health and the incidence of low-trauma fractures in multiple sclerosis are more related to impaired gait than to extended corticosteroid therapy.