Single BMD, fracture history accurately predict fracture over 25 years

By Will Boggs MD

NEW YORK (Reuters Health) - A single bone mineral density (BMD) measurement and fracture history accurately predict the risk of fractures over the ensuing 20 to 25 years in postmenopausal women, according to results from the Study of Osteoporotic Fractures (SOF).

One standard-deviation decrease in BMD is associated with a doubling or tripling of future hip fracture risk and about a 50% increased risk for all nonvertebral fractures, but most studies have assessed this relationship over only three to five years.

A history of nonvertebral fractures is also associated with an increased risk of future fracture, but the longest follow-up of studies investigating this association is 16 years.

Dr. Dennis M. Black from the University of California, San Francisco, and colleagues used SOF data from more than 8,100 white women to investigate how well dual-energy x-ray absorptiometry (DXA) BMD and fracture history predict fracture risk for up to 25 years.

At the baseline visit, 38.4% of women reported a history of at least one nonvertebral fracture and 2.3% reported a history of hip fracture since age 50 years. The average femoral neck BMD T-score was -1.4.

Over the next 25 years, 15.9% of women experienced one or more hip fractures, and during 20 years of follow-up, 43.7% of women had one or more nonvertebral fractures, the researchers report in the Journal of Bone and Mineral Research, online July 18.

Femoral-neck BMD strongly predicted the long-term incidence of hip and nonvertebral fractures, even after adjusting for age and accounting for the competing risk of mortality.

Each standard-deviation decrease in baseline BMD was associated with a doubling of the relative hazard of hip fracture and a 50% increase in the relative hazard of nonvertebral fracture.

BMD remain strongly predictive of long-term hip fracture risk regardless of age at baseline (<70, 70-74, or 75+ years).

History of nonvertebral fracture was associated with a 40% increased risk of hip fracture over 25 years and a 60% increased risk of nonvertebral fracture over 20 years.

History of hip fracture was slightly more predictive of future hip fracture risk than was history of any nonvertebral fracture, whereas history of nonvertebral and hip fracture were equally predictive of nonvertebral fracture risk.

The predictive value of femoral-neck BMD for hip fracture and for nonvertebral fracture declined slightly across five-year intervals, but remained statistically significant.

The pattern was slightly different for fracture history: it predicted hip fracture risk for the first 15 years, but was not statistically significant thereafter. Its predictive value for nonvertebral fractures attenuated slightly over time, but remained statistically significant out to 20 years.

The researchers conclude that “hip BMD is a remarkably persistent predictor of hip and nonvertebral fractures over 20 to 25 years and that self-reported history of any fracture also remains predictive over the very long-term. By following this cohort of older women for so long, we show directly that lifetime risk of hip fracture in community-dwelling women over age 75 years is extremely high. These results strongly support the value of risk assessment and consideration of treatment even in the oldest, highest risk women.”

Dr. Tuan Nguyen from St. Vincent's Clinical School, UNSW Australia, in Darlinghurst, Australia, who has researched various aspects of osteoporosis and bone fractures, told Reuters Health by email, "I think the implication for patient management is that doctors do not need to re-measure BMD for assessing fracture risk. Another implication is that the loss of BMD with time is so small that it does not have a substantial impact on fracture risk.”

“I think it is important to distinguish between association and prediction here,” said Dr. Nguyen, who was not involved in the study. “Association is about effect of an outcome variable (e.g., fracture), whereas prediction is about classification of the outcome variable. The present data suggest that a single BMD measurement is associated with future fracture risk, but the data do not necessarily suggest that BMD can be used for predicting the risk of fracture up to 25 years.”

Dr. Black did not respond to a request for comments.

SOURCE: http://bit.ly/2u3Oo6V

J Bone Mineral Res 2017.

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