Vitamin D depletion in hip fracture women is associated with the occurrence of simultaneous upper limb fractures independently of bone mineral density

Abstract

IntroductionSevere vitamin D deficiency is associated with the occurrence of simultaneous fractures at both hip and upper limb due to a single fall. We hypothesized that reduced bone mineral density (BMD) could explain the association. MethodsWe investigated 549 white women consecutively admitted to a rehabilitation hospital because of their first fall-related hip fracture. Thirty-three (6%) of the 549 women sustained a concomitant upper limb fracture of either distal radius (24 women) or proximal humerus (nine women). We assessed serum levels of 25-hydroxyvitamin D, hip BMD by dual-energy X-ray absorptiometry, and spine deformity index scores by lateral spine radiographs, 19.5±7.1 (mean±SD) days after fracture occurrence. ResultsSerum levels of 25-hydroxyvitamin D were significantly lower in the 33 women with concomitant fractures of both hip and upper limbs than in the remaining 516 (mean difference between groups 5.6ng/ml, 95% CI from 3.5 to 7.6, P<0.001). Conversely, no significant differences were found in hip BMD or spine deformity index scores between the two groups. After adjustment for eight potential confounders, the occurrence of simultaneous fractures due to a single fall was significantly associated with low levels of 25-hydroxyvitaimn D (P=0.001), but not with femoral BMD or spine deformity index scores. ConclusionThe association between severe vitamin D deficit and the occurrence of concomitant fractures at both hip and upper limbs due to a single fall is independent of femur BMD. Further investigations should focus on altered fall pattern or reaction to fall.