Osteoporosis in older men and women is a public health problem around the world, especially as people in many countries live longer. As bones become more fragile with age, they are more likely to break or fracture. In some countries, the lifetime risk of an older woman having either a hip, wrist or vertebral fracture is between 40 and 50 percent.

"Hip fractures are the most devastating consequence of osteoporosis," according to Dr. Jane Cauley from the University of Pittsburgh School of Medicine. She points out that many older people who fracture a hip die within one year of the incident, and many more lose their independence. "Fifty percent of women or men after their hip fractures aren't able to carry out their activities of daily living."

Cauley was one of the international researchers who worked on the trial of a drug called zoledronic acid. It is a member of a class of drugs called bisphosphanates, which have been used for decades to prevent the bone density loss associated with developing osteoporosis.

One interesting property of these medications, Cauley notes, is how long they stay active in the body, a property known as half-life. "The half-life is ten years or more, and that's why they can be given intermittently, and the patterns of use of some of the oral bisphosphanates is at least weekly or monthly."

In the trial, Cauley and the other researchers gave 4,000 women a single yearly intravenous infusion of zoledronic acid and studied what happened to their rate of hip fractures. They compared those women to another 4,000 women who received a placebo. The study lasted for three years.

Cauley reports that women in the first group experienced a significant reduction in their risk of fracture. "Their risk of vertebral fracture was reduced by 70 percent, their risk of hip fracture was reduced by 40 percent and all fractures were reduced by about 25 percent."

The researchers will continue to study all the women for at least three more years.

Cauley notes that funding for the research is being provided by the company that manufactures zoledronic acid. The research was published in a recent issue of the New England Journal of Medicine.