David A. Barondess

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.

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 Womens 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.

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 ≥ 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%.

Comparison of Cross‐Sectional Geometry of the Proximal Femur in White and Black Women from Detroit and Johannesburg

There are known black‐white differences in bone density measured by DXA but less is known about bone architecture. We compared cross‐sectional geometric properties of the proximal femur in U.S. black (n = 86) and white (n = 151) and South African black (n = 60) and white (n = 48) postmenopausal women. Results are consistent with greater bone strength in the black groups in both countries.

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.

Alcohol consumption associated with collegiate American football pre-game festivities

Internationally, sporting events represent a specific context in which heavy episodic drinking is common. The current study assessed determinants of heavy episodic drinking among tailgaters (i.e., individuals engaging in pre-game social festivities) prior to American football games at two large universities. A total of 466 individuals at two universities completed a short interview and provided a breathalyzer sample to estimate breath alcohol content (BrAC) during the tailgating window (150min prior to and 10min after the start of the game). The plurality of participants, 48.5% at the southeastern university (School1) and 58.8% at the midwestern university (School2), engaged in heavy episodic drinking. Only 54 individuals (11.6%) from the combined sample at both universities abstained from alcohol (confirmed via BrAC). In total, 40.2% of participants at School1 and 31.9% at School2 produced breath samples over the legal limit for driving (i.e., BrAC=0.08 or higher). In site-specific regression analyses, younger ages, males, and non-students at School1, and younger ages and non-game attendance at School2 were associated with self-reported heavy episodic drinking and higher levels of estimated BrAC (p<0.05). Given the widespread participation in heavy episodic drinking among both students and non-students in this sample, public health interventions should be implemented both on- and off-campus to promote safety and to discourage heavy episodic drinking at American football games and other high-profile sporting events.

Uncovering Local Trends in Genetic Effects of Multiple Phenotypes via Functional Linear Models

Recent technological advances equipped researchers with capabilities that go beyond traditional genotyping of loci known to be polymorphic in a general population. Genetic sequences of study participants can now be assessed directly. This capability removed technology‐driven bias toward scoring predominantly common polymorphisms and let researchers reveal a wealth of rare and sample‐specific variants. Although the relative contributions of rare and common polymorphisms to trait variation are being debated, researchers are faced with the need for new statistical tools for simultaneous evaluation of all variants within a region. Several research groups demonstrated flexibility and good statistical power of the functional linear model approach. In this work we extend previous developments to allow inclusion of multiple traits and adjustment for additional covariates. Our functional approach is unique in that it provides a nuanced depiction of effects and interactions for the variables in the model by representing them as curves varying over a genetic region. We demonstrate flexibility and competitive power of our approach by contrasting its performance with commonly used statistical tools and illustrate its potential for discovery and characterization of genetic architecture of complex traits using sequencing data from the Dallas Heart Study.

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 Rochersquo;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.