Cross-sectional geometry, bone strength, and bone mass in the proximal femur in black and white postmenopausal women.

Osteoporosis is characterized by both a low bone mass and a disruption of the architectural arrangement of bone tissue, leading to decreased skeletal strength and increased fracture risk. Although there are well-known ethnic differences in bone mass and fracture risk, little is known about possible ethnic differences in bone structure. Therefore, we studied cross-sectional geometry in the hip in a sample of postmenopausal black and white women in order to investigate ethnic differences that might contribute to differences in bone strength and ultimately hip fracture risk. We recruited 371 postmenopausal black and white women who were entering the Women's Health Initiative (WHI) clinical trials in Detroit. Bone density measurements of the proximal femur were done by dual-energy X-ray absorptiometry (DXA) using a Hologic 1000 Plus bone densitometer. The DXA data were used for hip structure analysis, which treats the entire proximal femur as a continuous curved beam from the proximal shaft to the femoral neck. This permits the analysis of cross-sectional geometric properties in two narrow regions corresponding to thin (5 mm) cross-sectional slabs seen on edge. The results indicate significant ethnic differences in bone density, cross-sectional geometry, and dimensional variables. Specifically, the black women have a significantly higher bone density in both locations (10.1% and 4.1% for the neck and shaft, respectively); greater cross-sectional geometric properties in the neck (ranging from 6.1% to 11.6%), but a smaller endocortical diameter in the neck (3.6%). There are fewer significant differences in cross-sectional geometry in the shaft location. Our data suggest that the spatial distribution of bone is arranged in the femoral neck to resist greater loading in black women compared with white women.

A noninvasive measure of physical maturity as a predictor of bone mass in children.

OBJECTIVE: The purpose of this study was to describe the accumulation of whole body bone mass in a longitudinal study of prepubertal boys and girls using Roche's physical maturity index as a measure of developmental age. METHODS: We measured 561 children (39% white, 61% African-American) from a suburban school district, representing an ethnically mixed, middle-class community adjacent to Detroit. Anthropometric measures taken for the present study included recumbent length (cm), stature (cm), weight (kg), whole body bone mineral content (WBBMC in g) and a noninvasive measure of physical maturity (PM%). PM% was calculated from published formulae derived from data from the Fels Longitudinal Study, using recumbent length, weight, midparental stature, age, and age- and gender-specific regression coefficients. RESULTS: At average age 9.9 (+/-0.6) years, there were no significant gender differences in stature, recumbent length, weight, or WBBMC in either ethnic group. Average PM for girls was significantly greater than that for boys within each ethnic group. There were no significant ethnic differences in PM in either gender. Stature and WBBMC were significantly different in the two ethnic groups for both boys and girls. Regressions of WBBMC on PM and chronological age indicated that PM explained more of the variance in WBBMC than did age (r2 ranging from 0.28 to 0.75 for PM versus 0.01 to 0.06 for age). In the case of African-American boys, r2 was similar (0.09 for PM and 0.06 for age). CONCLUSIONS: PM is a useful, noninvasive measure of developmental age that is significantly correlated with bone mass in children. Our study also indicates that PM is a better predictor of WBBMC than chronological age. Because PM can be calculated without using invasive and potentially expensive methods, PM may be useful in some clinical as well as research settings.

Whole body bone, fat and lean mass in children: comparison of three ethnic groups.

We measured whole body bone, fat and lean mass, by dual-energy x-ray absorptiometry, of third-grade children in a suburban public school district adjacent to Detroit. Of 1,340 eligible children, 773 participated. Using U.S. Census categories, parents identified their children as black/African-American (57%), white (38%), or one of several other categories (5%). Some of the participants also identified with a relatively large Middle Eastern subgroup (Chaldeans). Of the 773 participants, 734 are included in this report (71 Chaldeans, 226 whites, and 437 black/African-Americans; other categories are omitted). We describe body size, body composition, and physical activity levels in the three groups. The Chaldean and black children have significantly higher average whole body bone mineral content (BMC) than whites (P > 0.05), but are not different from each other. Lean mass and height are significantly greater for Chaldeans and blacks than for whites. The ratio of BMC to height was also significantly greater in Chaldeans and blacks compared with whites. Chaldeans have a significantly higher weight and fat mass than either the black or white children, and report significantly less physical activity than either the white or the black children. The higher bone mass among the Chaldean children may be partially explained by their greater body mass, but there is no readily apparent explanation for the observed ethnic differences in body size. We cannot exclude genetic or environmental factors not evaluated in this observational study. Our unexpected finding that Chaldean children, when analyzed as a separate group, are more similar in body composition to black/African-American than to white children contributes to a growing body of literature indicating that the uncritical use of "race" categories may obscure rather than facilitate the identification of population differences.

Whole body bone, fat, and lean mass in black and white men.

This research describes the effects of age, ethnicity, and body size and composition on whole body bone mass and bone density in healthy black and white men. We measured 79 male subjects, 42 white and 37 black, ranging in age from 33 to 64 years. Whole body bone mineral content (WBBMC) and bone mineral density (WBBMD), as well as fat and lean mass, were evaluated with a Hologic 1000W bone densitometer. We explore the utility of different methods of controlling for variations in body size in the two ethnic groups. There are statistically significant ethnic differences only in the bone mass variables. The black men had a 15% higher WBBMC (3111 vs. 2712 g, p < 0.0001) and a 8% higher WBBMD (1.25 vs. 1.16 g/cm2, p = 0.001) than the white men. Dividing WBBMD by height reduced the black/white difference to 6%. WBBMC, WBBMC/height, and WBBMD are strongly and significantly correlated with weight, body mass index (BMI), and body composition; correlations tended to be lower for WBBMD/height. Age is not significantly correlated with any of the variables in either ethnic group (p > or = 0.10). In multivariate linear regression models for predicting WBBMC or WBBMD, the two best models contained height, weight, and an interaction of ethnicity and weight (model r2 = 0.72 for WBBMC and r2 = 0.47 for WBBMD); and height, lean mass, and an ethnicity-fat interaction (model r2 = 0.69 for WBBMC and r2 = 0.46 for WBBMD). Using analysis of covariance, we found that controlling for lean mass and height reduced the black/white difference in bone mass from 14.7 to 9.8%.

The accumulation of whole body skeletal mass in third- and fourth-grade children: effects of age, gender, ethnicity, and body composition.

The purpose of this longitudinal study is to describe bone mass and body composition, and the annual changes in these measurements, among third grade students recruited from a suburban school district. Whole body bone mineral content (WBBMC), bone mineral density (WBBMD), fat, and lean mass were measured by dual-energy X-ray absorptiometry. Bone mass in the lumbar spine (LBMC) region of the whole body scan was also utilized. 773 students (38% white, 57% black, 5% other) had baseline visits; 561 had a second measurement a year later. At baseline, black children have significantly higher WBBMC, WBBMD, height, and lean mass than whites. Black males, but not black females, have a greater LBMC. There are no significant gender differences in body size, WBBMC, or WBBMD, although girls have a greater LBMC and fat mass, and boys have a higher lean mass. Most of these differences persist in visit 2. The annual change in bone and lean mass is greater in blacks. Stepwise linear regression analyses of bone mass on body size, gender, and ethnicity and their interactions indicate that log-transformed weight explains most of the variance in both WBBMC and WBBMD (multiple r2 = 0.90 and 0.64, respectively). There are significant black/white differences in intercepts and slopes. Other variables explain only another 1%-2% of the variance. The strongest Pearson correlations are between changes in bone mass and changes in lean mass and log-transformed weight (r ranging from 0.62 to 0.84, p = 0.0001). We conclude that there is a significant black/white, but not male/female difference in whole body bone mass and bone density before puberty. Ethnic and gender differences in bone and body composition suggest that the lean component may contribute to a greater peak bone mass in blacks vs. whites, and perhaps in males vs. females.

Ethnic differences in regional bone density, hip axis length, and lifestyle variables among healthy black and white men.

There are few published data on bone mass, measured by dual-energy X-ray absorptiometry (DXA), in healthy white or black men. Similarly, a recently described predictor of hip fracture among white women, hip axis length (HAL), has not been studied in men. We recruited 160 white and 34 black men, aged 23-80 years, and screened for diseases and drug exposures that adversely affect skeletal health. We measured bone mineral density (BMD) in the lumbar spine, femoral neck, and radial shaft by DXA; height and weight; skin color by reflectometry; and hip axis length both directly from DXA output and using automated software in a subsample. We also obtained historical data on education, smoking, exercise, and fractures. There were no significant black/white differences in mean weight, height, body mass index (BMI), or HAL. The black men had higher BMDs than did the white men at every site (5% for the radius, 10% for the lumbar spine, and 20% for the femoral neck). Skin pigmentation and BMD were not significantly correlated in either group (p > 0.38). Among the white men, smoking was associated with lower lumbar BMD, but there was no significant relationship between BMD and exercise frequency in either group. There was no significant ethnic difference in fracture experience. We conclude that: (1) the higher BMD in black men than in white men is not due to greater body size, (2) the lower hip fracture risk reported for black men than for white men is not due to a difference in hip axis length; (3) skin color is not related to BMD in either sex.

The effects of aging on the comparability of antemortem and postmortem radiographs.

To study the effects of aging on the ability to make positive identifications from radiographs of the postcranial axial skeleton, we collected early and later exposed abdominal X-rays from five patients whose period of treatment spanned from ten to twenty-three years. Corresponding lumbar vertebrae from each pair of radiographs were compared for similarities and differences in several of the criteria that have been reported as useful for individualization. These include shapes of the bodies, spinous processes, transverse processes, pedicles, and osteophytic extrusions. It is our conclusion that even though bone is a flexible tissue and changes constantly during life, aspects of the criteria chosen are quite stable and that even after two-and-a-half decades the ability to make positive identifications from postcranial axial material is not necessarily diminished.