* Fractures down 32 percent in women, 25 percent in men
* Osteoporosis drugs do not explain entire decrease

Hip fracture rates have declined among the elderly for a variety of reasons, but the disabling injury is still a major health threat as populations age, Canadian researchers said on Tuesday.

A steady year-over-year decline in fracture rates since 1985 predates widespread use of drugs used to treat osteoporosis and preserve bone density, the researchers said, even though drugs that first entered the market in the mid-1990s likely played a role.

I don't honestly think there's just one factor that accounts for all of this, said Dr. William Leslie of the University of of Manitoba in Winnipeg, who led the study published in the Journal of the American Medical Association.

Between 1985 and 2005, more than 570,000 Canadians were treated for hip fractures. Over those two decades, the rate of hip fractures declined 32 percent in women and 25 percent in men, with the largest decrease among adults aged 55 to 64.

A fractured hip can lead to complications from surgery such as infections, pneumonia, and blood clots arising from the loss of mobility. One in five elderly who suffer a hip fracture die within a year.

While fracture rates have declined since 1985, the overall number in North America and Europe has climbed as populations age. Worldwide, there are 9 million new hip fractures related to declining bone density every year, the report said.

The point is, there's no time for complacency, Leslie said in a telephone interview.

We can identify with bone density testing those with higher risk of hip fracture, and medications in the appropriate individuals are quite helpful in reducing the risk, he said.

Possible factors in the decline in fracture rates include better nutrition throughout life that has a lasting impact on bone health, more attention to the risk of falls, improved diagnostic and treatment options for those with thinning bones, and, curiously, higher rates of obesity, Leslie said.

Overweight people tend to suffer less from osteoporosis because they have more bone-strengthening hormones circulating in their bodies and more padding to protect hips during falls. Underweight people are also more at risk of osteoporosis.

We are in no way advocating obesity, Leslie said. People that are immobile tend to lose muscle strength and balance, so they be more at risk for falls.

Drugs used to strength bones include a class of products known as bisphosphonates. Among them are Merck & Co's (MRK.N) Fosamax, Roche Holding AG's (ROG.VX) Boniva, Novartis AG's (NOVN.VX) (NVS.N) Reclast, Procter and Gamble Co's (PG.N) Actonel, Sanofi Aventis' (SASY.PA) (SNY.N) Skelid and Novartis' Aredia and Zometa.

(Editing by Maggie Fox and Alan Elsner)

Medicine Canada