RESEARCH - Bone-loss rate predicts fracture risk regardless of baseline BMD

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Bone-loss rate predicts fracture risk regardless of baseline BMD

Rheumawire

Sep 8, 2005

Janis

Sydney, Australia - The rate of bone loss at the femoral neck predicts

fracture risk independently of baseline bone-mineral density (BMD) and age,

according to Dr Tuan V Nguyen (Garvan Institute of Medical Research, St

's Hospital, Sydney, Australia) [1]. Nguyen reports in the July 2005

issue of the Journal of Bone and Mineral Research that a 5% loss of femoral

neck BMD translates into a 40% increase in the risk of fracture in normal,

ambulatory elderly women.

" At present, depending on the country, women with low BMD (eg, osteoporosis)

or a recent history of fracture are eligible for treatment [with

antiresorptive agents]. Women whose BMD is above the threshold of

osteoporosis and without any other osteoporosis symptoms are not treated.

Results of our study suggest that those with low BMD (not necessarily

osteoporosis) who have excessive bone loss should also be considered for

treatment, " Nguyen tells rheumawire.

Tiny increase in bone-loss rate causes large increase in fracture risk

This study, which Nguyen says was the first to assess the rate of bone loss

and fracture in the general population, used data from the ongoing Dubbo

Osteoporosis Epidemiology Study (DOES). The investigators analyzed data from

966 women, mean age 69.9 years, who had at least two BMD measurements

separated by an average interval of 2.7 years. Average duration of follow-up

was 10.7 years.

During the follow-up period there were 43 hip fractures, 71 symptomatic

vertebral fractures, 37 proximal humerus fractures, 46 forearm and wrist

fractures, and 27 rib and pelvis fractures. About two thirds of the fracture

subjects were older than 70 years of age.

Multivariate analysis identified age, baseline femoral-neck BMD, and rate of

bone loss as independent predictors of fracture risk overall. Rate of

femoral-neck bone loss was significantly associated with hip, symptomatic

vertebral, and proximal humerus fractures (but not with fractures at other

sites), and this association was independent of femoral-neck BMD and age.

Each 0.12 g/cm2 loss in femoral-neck BMD was associated with a 3.1-fold

increase in hip-fracture risk.

The researchers note that since 45% of fractures could be attributed to

osteoporosis, high rate of bone loss, and advancing age, effective primary

prevention of bone loss beginning before menopause might have a significant

effect on the incidence of fractures in the general population.

This study also might help explain clinical-trial data showing that

antiresorptive therapies such as potent bisphosphonates produce only a

modest 4% to 8% increase in BMD but reduce the rate of fractures by half.

Nguyen thinks this might reflect changes in the rate of bone loss.

" Low BMD accounts for about half of fracture cases. The question is which

other factors account for the rest? In this study we show that bone loss,

even short-term bone loss, is an independent factor that accounts for some

of the fracture cases that are not explained by low BMD. In the field of

osteoporosis, people have been talking about 'bone loss' and fracture risk

for a long time, but strictly, what they have talked about is 'low bone

density,' not 'loss,' because of the lack of longitudinal data. This is the

first longitudinal study that demonstrates that bone loss is a risk factor

for fracture risk. Therefore, osteoporosis is not just a disease of low bone

density; excessive bone loss is also a risk factor, " Nguyen says.

Source

1. Nguyen TV, Center JR, Eisman JA, et al. Femoral neck bone

loss predicts fracture risk independent of baseline BMD. J Bone Miner Res

2005; 20:1195-1201.

Not an MD

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Mayo Clinic in Rochester

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