Single BMD Scan Predicts Future Fracture Risk in Older Women

Pam Harrison

July 21, 2017

A single measurement of bone mineral density (BMD) at the femoral neck in women 67 years of age and older predicts a woman's risk of having either a nonvertebral or hip fracture over the next 20 to 25 years, respectively, a new analysis of the Study of Osteoporotic Fractures (SOF) indicates.

Also strongly predictive of a woman's risk of fracture over the long term is a history of any nonvertebral fracture, say Dennis Black, PhD, University of California, San Francisco, and colleagues in their study published online July 18, 2017 in the Journal of Bone and Mineral Research. 

The ability of BMD and other risk factors to predict fracture risk is well-established for 5 to 10 years, but their value in predicting longer-term risk had not previously been studied, they explain.

"We conclude that a single BMD and fracture history assessment [in a woman aged 65 years and older] can predict fracture risk over 20 to 25 years," they state.

They also discovered that remaining lifetime fracture probability seems to be higher than previously indicated, approximately twice as high, among women over aged 65 years ― who had a 25-year risk of hip fracture of almost 18%.

And in those aged over 80, they found a 25-year risk for hip fracture of 23%, which is at least as high as seen in similar studies.

Dr Black told Medscape Medical News that some healthcare professionals believe that "the 10-year risk of hip fracture goes down as people get older because of competing mortality risks."

"But this study really dispels this thinking. So one of the important messages from this paper is that physicians should be paying attention to the oldest women, as their risk of hip fracture is very high, and they should be screened [for risk factors] and potentially treated [for osteoporosis] if they meet guideline criteria." 

"Treatment — which has been shown to be safe and effective in the oldest of the old — can prevent the devastating consequence of fracture," he added.

History of Any Fracture An Important Predictor

Dr Black and colleagues used data from the SOF cohort of 7959 primarily Caucasian women, mean age 73.4 years, among whom BMD was first measured by dual-energy X-ray absorptiometry (DXA) between 1988 to 1990.

Overall, 38.4% of women reported a history of at least one nonvertebral fracture, while 2.3% of the cohort reported a history of experiencing a hip fracture from age 50 years onwards.

Over the next 20 years of follow-up, 43.7% of women had one or more nonvertebral fractures, while 15.9% of the cohort sustained one or more hip fractures over the next 25 years.

There has been some controversy about whether the history of hip fracture is superior to that of nonvertebral fractures in predicting risk of future hip fracture, the authors say.

"Our results showed no important advantage to history of hip fracture compared with history of any nonvertebral fracture for predicting subsequent fracture," they note.

"Moreover, a history of any fracture is much more common than a history of hip fracture, and therefore will be more useful on a population level as a predictor."

BMD at Femoral Neck Is Strongly Predictive

BMD at the femoral neck was "strongly predictive" of the long-term risk of both hip and nonvertebral fractures — even after accounting for competing mortality risks.

The long-term risk of having a hip fracture was almost five-fold higher over the next 25 years for women in the lowest BMD quartile (29.6%) compared with those in the highest BMD quartile (7.6%).

Corresponding rates for nonvertebral fracture were almost twice as high among women in the lowest BMD quartile (59.7%) vs the highest BMD quartile (32.9%).

And, "BMD remained very strongly predictive within each age group," the investigators observe.

For example, in women over age 75 years at baseline, the risk of sustaining a hip fracture over the next 25 years went from a low of 7.1% for women with a femoral neck T-score in excess of –1.0 to a high of 31.5% for women with a T-score below –2.5 at baseline. 

Still, "as expected, the cumulative incidence of both hip and nonvertebral fractures was related to age," the researchers note.  

For women over age 80 years at baseline, the risk of sustaining a hip fracture over 25 years was 22.6%, compared with only 13.9% for women under age 70 years at baseline.

For nonvertebral fracture, women over age 80 years at baseline had a 50% risk over the next 20 years, compared with 42.6% of women under age 70 years at baseline. 

Only One BMD Measurement Needed

Explaining that their results show just a single BMD measurement is sufficient to predict fracture risk, Dr Black told Medscape Medical News: "Some have suggested that BMD measurements should be done very frequently, such as every year or every 2 years, in older women."

"But we found that [a single measure of] bone density is a very strong predictor of a very important disease, which is fracture ― particularly hip fracture ― over the long term," he added.

"And while bone density can suddenly change if, for example, women start using glucocorticoids or there is marked weight loss," knowing a woman's single BMD measurement "can help you stratify patients in terms of how worried you are about their fracture risk. And if a woman has a BMD of –1 at the age of 65, you certainly don't have to worry about her for another 5 years," he added.

SOF is supported by the National Institutes of Health. Dr Black reports receiving grant support from Alexion and consulting fees from Amgen, Merck, Asahi-Kasei, and Radius.

J Bone Miner Res. Published online July 18, 2017. Abstract

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