Predicting hip fracture risk in postmenopausal women

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To help doctors predict the five-year risk of hip fractures in their postmenopausal patients, a team of UC Davis researchers has developed a method that assesses nearly a dozen factors, including age, ethnicity and level of physical activity.

Working with data from tens of thousands of women who participated in the Women’s Health Initiative (WHI), UC Davis professor of medicine and internist John Robbins and his colleagues evaluated the clinical risk factors associated with hip fractures in women and created a process that they say could be useful in making decisions about screening and the use of medications for osteoporosis.

The research team’s work is in a study that appears in the November 28 issue of The Journal of the American Medical Association (JAMA).

“Because of the hundreds of thousands of women involved in the Women’s Health Initiative, we were able to develop a more powerful tool for the prediction of hip fracture than has been possible before,” said Robbins. “Part of the power of our method is its ability to put multiple factors in the same model. For example, adults with diabetes tend to be heavier. We can see from the model that individuals who weigh more are less likely to have hip fractures but diabetic individuals are more likely to have them. The algorithm can balance these two factors.”

The High Cost of Hip Fractures

The estimated 329,000 hip fractures that occur annually in the United States are associated with a high rate of illness, death and high costs. Prevention of hip fracture is a high priority for patients, physicians and public-health officials, the researchers stated.

The study included data on a total of 93,676 women who participated in the observational component of the WHI, a multiethnic study. Factors were identified that were predictors of hip fracture, which were then validated using data on 68,132 women who participated in the clinical trial. The model also was tested in a subset of 10,750 women who had undergone dual-energy x-ray absorptiometry scans (DXA, an imaging technique) for bone mass density assessment, which is used to predict risk of hip fracture.

During an average follow-up of 7.6 years, 1,132 hip fractures were identified among women participating in the observational study (annualized rate, 0.16 percent), while during an average follow-up of eight years, 791 hip fractures occurred among women participating in the clinical trial (annualized rate, 0.14 percent).

Eleven Factors for Predicting Hip Fractures

The study identified 11 factors that were predictive of hip fracture within five years: age, self-reported health, weight, height, race/ethnicity, self-reported physical activity, history of fracture after age 54, parental hip fracture, current smoking, current corticosteroid use and treated diabetes. Incorporating these factors into a clinical algorithm was useful in predicting the five-year risk of hip fracture among postmenopausal women of various ethnic backgrounds.

Robbins and his research colleagues indicated that further studies are needed to define the clinical implications of the algorithm and to confirm treatment benefits for those women who are considered to be at an increased risk for hip fracture. Ultimately, they said, the decision about whom to further screen for osteoporosis and whom to treat will need to be based on available resources and major social and political judgments.

The study concludes that knowing the five-year risk of fracture will permit patients and physicians to make informed choices when balancing making lifestyle changes against undergoing medical interventions.

Source: UC Davis Health System, USA

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