LONG-TERM EFFECTS OF CALCIUM SUPPLEMENTATION ON BONE LOSS AND FRACTURES IN POSTMENOPAUSAL WOMEN - A RANDOMIZED CONTROLLED TRIAL

PURPOSE: To determine the long-term effects of calcium supplements or placebo on bone density in healthy women at least 3 years postmenopaus e. PATIENTS AND METHODS: Eighty-six women from our previously reported 2-year study agreed to continue on their double-blind treatment alloc ation (1 g elemental calcium or placebo) for a further 2 years, with 7 8 women (40 on placebo) reaching the 4-year end point. Median (interqu artile range) dietary calcium intakes for the whole group were 700 mg (range 540 to 910) per day at baseline, 670 mg (range 480 to 890) per day at 2 years, and 640 mg (range 460 to 880) per day at 4 years. The bone mineral density (BMD) of the total body, lumbar spine, and proxim al femur was measured every 6 months by dual-energy, x-ray absorptiome try. RESULTS: There was a sustained reduction in the rate of loss of t otal body BMD in the calcium group throughout the 4-year study period (P = 0.002), and bone loss was significantly less in the calcium-treat ed subjects in years 2 through 4 also (difference between groups 0.25% +/- 0.11% per year, P = 0.02). In the lumbar spine, bone loss was red uced in the calcium group in year 1 (P = 0.004), but not subsequently. There was, however, a significant treatment effect at this site over the whole 4-year period (P = 0.03). In the proximal femur, the benefit from calcium treatment also tended to be greater in the first year an d was significant over the 4-year study period in the femoral neck (P = 0.03) and the trochanter (P = 0.01). Nine symptomatic fractures occu rred in 7 subjects in the placebo group and 2 fractures in 2 subjects receiving calcium (P = 0.037). CONCLUSIONS: Calcium supplementation pr oduces a sustained reduction in the rate of loss of total body BMD in healthy postmenopausal women.