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

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 5.6 ng/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.