Racial differences in bone strength

Abstract

Osteoporosis has been defined as a systemic skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. The clinical consequences of fracture include short- and long-term morbidity as well as increased mortality. Several authors have examined data from the Health Care Financing Administration and noted that fracture risk, particularly risk of hip fracture, is higher in whites than blacks in both sexes; the most recent published data reported an age-adjusted annual incidence rate for hip fracture of 10.1 and 4.1 per 1000 in white and black women, respectively, and 4.3 and 3.1 per 1000 in white and black men, respectively. Other analyses estimated the actuarial risk of hip fracture of persons age 65 by age 90 to be 16.3 and 5.3 percent in white and black women, respectively, and 5.5 and 2.6 percent in white and black men, respectively. This lower incidence of fractures among blacks has generally been explained by greater bone strength among blacks, although differences in non-skeletal risk factors for fracture, such as falls, cannot be completely excluded. Data from the Study of Osteoporotic Fractures (SOF) and the Baltimore Men's Osteoporosis Study (MOST) show that, in both sexes, blacks have higher adjusted bone mineral density than whites and a slower age-adjusted annual rate of decline in bone mineral density. Genetic, nutritional, lifestyle and hormonal factors may contribute to these ethnic/racial differences in bone strength.

Fig. 1

Average annual age-adjusted incidence rates for hip fracture among whites and blacks, by sex, in the United States, 1992–1993.

Fig. 2

Mean bone mineral density at the femoral neck and total hip among 7334 older white and 636 older black women enrolled in the Study of Osteoporotic Fractures. Standard deviations for femoral neck BMD among white and black women were 0.11 and 0.15 g/cm2, respectively, and for total hip BMD among white and black women were 0.13 and 0.15 g/cm2, respectively. Distributions were significantly different by race at each site with P < 0.01.

Fig. 3

Mean bone mineral density at the femoral neck and lumbar spine among 503 older white and 191 older black men enrolled in the Baltimore Men's Osteoporosis Study. Standard deviations for femoral neck BMD among white and black men were 0.13 and 0.15 g/cm2, respectively, and for lumbar spine BMD among white and black men were 0.19 and 0.20 g/cm2, respectively. Distributions were significantly different by race at each site with P < 0.01.

Fig. 4

Average annual age-adjusted mean percent change in bone mineral among 6007 older white and 482 older black women enrolled in the Study of Osteoporotic Fractures. Distributions were significantly different by race at each site with P < 0.001.

Fig. 5

Average annual mean percent change in bone mineral among 349 older white and 119 older black men enrolled in the Baltimore Men's Osteoporosis Study. Distributions were significantly different by race at each site with P ≤ 0.01.