TUESDAY, May 3, 2005 (HealthDayNews) -- While bone mineral density levels are a key predictor of the risk of fractures in older women, they seem to be less so in older black women, a new study suggests.
Black women had a 30 percent to 40 percent lower risk of fracture, compared to white women, no matter what their bone mineral density levels were, University of Pittsburgh researchers found.
According to the report in the May 4 issue of the Journal of the American Medical Association, newly released information on bone health and osteoporosis from the U.S. Surgeon General says that one out of two individuals older than 50 are at risk for fractures from osteoporosis.
The government report noted that osteoporosis is a risk for any older man or woman with low bone mineral density (BMD), and BMD is an important predictor for fracture risk. But whether it is associated with fractures in older black women, who have lower fracture rates in general, has not been known.
"It has been well-established in white women that measures of bone mineral density can be used to identify women at risk of fracture," said study author Jane A. Cauley, a professor of epidemiology at the University of Pittsburgh. "However, the information in nonwhites has been lacking."
In their study, Cauley's team collected data on 7,334 white women aged 67 to 99 and 636 black women aged 65 to 94. The women all participated in the Study of Osteoporotic Fractures and were followed for an average of 6.1 years, according to the report.
"We found that the relationship between bone density and the risk of fracture within the African-American women was very similar to what we observed in the Caucasian women," Cauley said. "Women with low bone mineral density had a higher rate of fractures."
This suggests that measurements of bone mineral density in black women can be used to identify women at risk of fracture, she said.
However, Cauley said that when they combined the data of white and black women, they found that at every bone density level, the fracture rate among black women was 30 to 40 percent lower than among white women.
"Even among the women with the lowest level of bone density, the fracture rate of African-American women was still 30 to 40 percent lower than white women, and that was the same when we looked at women who had high bone density," she noted.
Cauley said that these findings suggest that other factors beyond bone mineral density are involved in the risk of fractures among black women. "These other factors could include hormones, the rate of bone regeneration or genetic factors."
Cauley believes all older women should have their bone density checked, so that those who are at risk for fracture can receive treatment. "We want to identify women at high risk of fracture," she said. "These women may benefit from different interventions, and bone density can be used to identify these women.
"The paper is interesting, and it tends to confirm the current observations that lower bone mineral density values are associated with increased risk of non-spinal fractures in both black and white women," said Dr. Stephen Honig, director of the Osteoporosis Center at New York City's Hospital for Joint Diseases.
Honig notes that the study suggests the reasons that black women have lower rates of fractures may be related to lower bone turnover, racial differences in hip axis length or bone size differences.
"This concept relates to bone turnover, repair, size and connectivity, and factors related to bone strength, but these references are only conjecture, since bone biopsies and other technologically difficult studies were not conducted as part of this study," Honig said.
"The bottom line," he said, "is that black women have the same concerns regarding fracture risk as white women, but overall are much less likely to sustain non-spinal fracture, even with the same profile as white women."
In an accompanying editorial, Dr. Louise S. Acheson, from Case Western Reserve University argues that race is not a good measure to use in treating osteoporosis, since it is often tough to distinguish one racial group from another based on superficial characteristics.
"An important issue is whether evidence about ethnic differences indicates a different threshold for treating patients with the same bone mineral density based on differences in skin color, facial features, or self-identified racial groups," Acheson wrote.
"This approach is fallible to the extent that race is a non-biological category, an extremely crude surrogate for biological, environmental, cultural and behavioral differences among individuals and human populations," she adds.
Acheson notes that factors other than race might be better in determining the best course of treatment. "If, besides bone mineral density, bone geometry, body composition, bone metabolism, physical capacity, fall risk, and eventually genotype are race-related variables determining fracture risk, measurements related to these factors could be evaluated clinically. Research will be needed to test their value. This step will be more appropriate than using race as a variable to determine treatment threshold," she concluded.
The National Institutes of Health can tell you more about osteoporosis.