Oestrogen plus a progestin increased bone density in the spine by 5 per cent and in the hip by 3.9 per cent in elderly women, says a study led by Creighton University researcher J. Chris Gallagher, MD, Professor of medicine and head of the Women's Health Centre. "The addition of an active form of vitamin D (calcitrol) to oestrogen further increased bone density in the spine by 7 per cent and in the hip by 5.3 per cent," he said. About 500 elderly women enrolled in the three-year study, which was supported by the National Institute on Ageing . Additionally, the researchers found that the use of vitamin D significantly reduced the number of falls that elderly women suffered over three years by about 30 per cent and also tended to reduce the chance of fractures. The results of the study, published in the Journal of Clinical Endocrinology and Metabolism, show that such combination therapy can increase the number of women who respond to therapy and increase the gain in bone density. According to Dr. Gallagher, combination therapy may offer benefits that are not achieved with single-medication therapy. "Combination therapy is best used in women who lose bone on a single drug, or who present with multiple fractures," he said.