Background: Hypovitaminosis D and a low calcium intake contribute to increased parathyroid function in elderly persons. Calcium and vitamin D supplements reduce this secondary hyperparathyroidism, but whether such supplements reduce the risk of hip fractures among elderly people is not known.
Methods: We studied the effects of supplementation with vitamin D₃ (cholecalciferol) and calcium on the frequency of hip fractures and other nonvertebral fractures, identified radiologically, in 3270 healthy ambulatory women (mean [±SD] age, 84±6 years). Each day for 18 months, 1634 women received tricalcium phosphate (containing 1.2 g of elemental calcium) and 20 μg (800 IU) of vitamin D₃, and 1636 women received a double placebo. We measured serial serum parathyroid hormone and 25-hydroxyvitamin D (25(OH)D) concentrations in 142 women and determined the femoral bone mineral density at base line and after 18 months in 56 women.
Results: Among the women who completed the 18-month study, the number of hip fractures was 43 percent lower (P = 0.043) and the total number of nonvertebral fractures was 32 percent lower (P = 0.015) among the women treated with vitamin D₃ and calcium than among those who received placebo. The results of analyses according to active treatment and according to intention to treat were similar. In the vitamin D₃—calcium group, the mean serum parathyroid hormone concentration had decreased by 44 percent from the base-line value at 18 months (P<0.001) and the serum 25(OH)D concentration had increased by 162 percent over the base-line value (P<0.001). The bone density of the proximal femur increased 2.7 percent in the vitamin D₃—calcium group and decreased 4.6 percent in the placebo group (P<0.001).
Conclusions: Supplementation with vitamin D₃ and calcium reduces the risk of hip fractures and other nonvertebral fractures among elderly women.