Ethnic differences in bone mass explained
MedWire News: Much of the racial heterogeneity in measures of bone mass can be accounted for by variation in body composition, diet, and socio-demographic factors, study results show.
"Given the aging of the US population and the accelerating epidemics of obesity and diabetes, the role of body composition in fall and fracture risk demands increased attention," say Andre Araujo (New England Research Institutes Inc, Watertown, Massachusetts, USA) and colleagues in the journal Osteoporosis International.
They report that Black Americans have a decreased risk for fracture, elevated bone mineral density (BMD), and lower rates of osteopenia and osteoporosis relative to their White peers.
These factors appear to outweigh Black Americans' disproportionate exposure to detrimental factors and their increased risk for syndromes of aging, notes the research team.
In the present study, the researchers analyzed data from Black, Hispanic, and White men enrolled in the Boston Area Community Health/Bone (BACH/Bone) Survey to determine the contributions of risk factors to racial/ethnic differences in bone composition.
Bone mineral content (BMC), BMD, and body composition were ascertained by dual-energy X-ray absorptiometry (DXA). Socioeconomic status, health history, and dietary intake were gathered through interview while hormones and markers of bone turnover were obtained from non-fasting blood samples.
The researchers found that Black men had significantly greater BMC than their Hispanic and White peers.
Multivariate regression analysis showed that lean and fat mass, serum 25 hydroxyvitamin D, osteocalcin, estradiol, and aspects of socioeconomic status (such as education and income) together accounted for around 60-70% of the magnitude of racial/ethnic differences in BMC - with lean and fat mass causing the strongest effects.
While absolute differences in BMC were smaller at the distal radius than femoral neck, the proportionate reductions in racial/ethnic differences after covariable adjustment were comparable or greater.
The results for BMD followed a similar pattern, but were typically of lesser magnitude and statistical significance.
Discussing the findings, the researchers note that femoral and distal sites differ in the relative proportion of trabecular or cancellous bone; at the femoral neck site, approximately 25% of the bone is trabecular, whereas in the distal radius, up to 10% is trabecular.
"Because trabecular bone is thought to be more metabolically active than compact bone, it is conceivable that BMC/BMD in the femoral neck would demonstrate stronger associations with covariables lying along metabolic pathways leading to osteogenesis and turnover than would BMC/BMD at the radius," they comment.
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By Andrew Czyzewski