May-Choo Wang

Bone mass and hip axis length in healthy Asian, Black, Hispanic, and white American youths

The primary objective of this study was to examine the associations of ethnicity, diet (calcium, protein, energy), and weight‐bearing activity with dual‐energy X‐ray absorptiometry (DXA)‐measured bone mass and hip axis length (HAL) in 423 Asians, blacks, Hispanics, and non‐Hispanic Caucasians, aged 9–25 years. Bone mass was expressed as bone mineral content (BMC), bone mineral density (BMD), and bone mineral apparent density (BMAD). The data were analyzed using multiple linear regression, after stratifying for gender and pubertal stage and adjusting for height and weight. With few exceptions, Asians and Hispanics had comparable bone mass to whites at all pubertal stages. Greater femoral neck BMAD in black than white females was observed at all pubertal stages. Black males displayed greater BMD and BMAD than white males at all sites in early puberty and at the femoral neck in maturity. Calcium was positively and protein negatively related to BMAD at the femoral neck in early pubertal females. Among males, calcium was negatively associated with whole body BMC and BMD and spine BMD and BMAD in midpuberty. Weight‐bearing activity was not associated with bone mass in females; in males, it was positively related only to femoral neck BMC in early puberty. There was an absence of evidence for ethnic differences in HAL among females. In males, we observed shorter HAL in mature Asians and blacks than whites. Neither diet nor activity was associated with HAL.

Bone acquisition and loss in children and adults with cystic fibrosis: A longitudinal study☆☆☆★★★

OBJECTIVES To determine patterns of bone mineral acquisition in children and young adults with cystic fibrosis (CF) and to identify clinical and laboratory correlates of change in bone mineral density (BMD). STUDY DESIGN Bone mineral and clinical status were assessed in 41 patients with CF (26 female, aged 9 to 50 years) at baseline and 1.5 years later. Bone mineral content of the lumber spine, femoral neck, and whole body was determined by dual-energy x-ray absorptiometry and expressed as BMD and bone mineral apparent density (BMAD). Changes in weight, height, pubertal status, glucocorticoid use, physical activity, disease severity, and biochemical markers of bone turnover were examined for associations with changes BMD and BMAD. RESULTS Mean BMD Z-scores (adjusted for age and sex) were reduced at the spine, hip, and whole body at baseline in both adults and youths, and decreased further at all sites among youths at follow-up (-0.4 at spine, p < 0.05; -0.3 at hip, p < 0.10; -0.5 for whole body, p < 0.0005). These data indicate failure to gain bone mineral at the expected rate. BMAD was also reduced at follow-up, suggesting that the observed osteopenia could not be explained by small bone size. Bone loss at multiple sites was observed in four youths and two adults. In general glucocorticoid use, change in body mass, physical activity, and disease severity were the most significant correlates for change in BMD and in BMD Z-score. CONCLUSIONS Osteopenia in CF generally reflects inadequate gains in bone mineral, although bone loss may occur, particularly in patients requiring glucoc therapy. Late gains in bone mineral may accompany weight gain and pubertal development, but the catch-up appears to be incomplete.

Associations of vitamin C, calcium and protein with bone mass in postmenopausal Mexican American women

We investigated the associations of vitamin C, calcium and protein intakes with bone mass at the femoral neck and lumbar spine in postmenopausal Mexican American women. Bone mass was measured by dual-energy X-ray absorptiometry (DXA) and expressed as areal (BMD, g/cm2) and volumetric (bone mineral apparent density or BMAD, g/cm3) bone mineral density. Diet was assessed using a modified version of the National Cancer Institute Food Questionnaire, which was administered by trained bilingual interviewers familiar with Mexican dietary practices. Data gathered from 125 subjects were analyzed using multiple linear regression analysis with age, body mass index (BMI), acculturation, years of estrogen use, physical activity, total energy intake, and the nutrient of interest as independent variables. Neither calcium nor calcium/protein ratio was associated with bone mineral density. There was evidence of a positive association between dietary vitamin C intake and femoral neck BMD (β=0.0002 g/cm2 per mg/day, SE=0.0001,p=0.07) and BMAD (β=0.0001 g/cm3 per mg/day, SE=0.00006,p<0.05), but vitamin C was not associated with lumbar spine bone mass. Further investigation of the role of vitamin C in skeletal health is warranted.

A Comparison of Calcaneus Ultrasound and Dual X-Ray Absorptiometry in Healthy North American Youths and Young Adults

Quantitative ultrasound is the newest noninvasive method to be accepted for assessing bone mineral in adults. Heel ultrasound measurements correlate with bone density measurements by dual X-ray absorptiometry (DXA) and predict fracture risk in adults. Far less is known about the value of calcaneus ultrasound (CUS) in children. We determine spine, femoral neck, and whole-body bone mineral by DXA and heel bone mass by CUS in 125 youths (69 females, 56 males) ages 9-25 yr. CUS and DXA measurements of bone mass increased with age and pubertal development during adolescence in a parallel fashion. Among females, Tanner stage was a stronger predictor than age for all CUS and DXA measurements, and among males, pubertal stage was a stronger predictor for spine bone mineral apparent density (BMAD) and femoral bone mineral density (BMD). CUS measurements correlated moderately well with DXA measurements of the spine, femoral neck, and whole-body BMD and spine BMAD (r = 0.23-0.58, p < 0. 008). CUS warrants further study as a tool for assessing bone mineral acquisition in children.

Ethnic Differences in Bone Mass of Young Women Vary with Method of Assessment

To examine ethnic differences in bone mass measured by calcaneus ultrasound (CUS) and dual energy X-ray absorptiometry (DXA), and to compare the two methodologies, CUS was performed in 904 healthy Asian, African American, Latina, and Caucasian women 20-26 yr old using the Lunar Achilles Plus ultrasonometer. CUS measurements (broadband ultrasound attenuation [BUA] and speed of sound [SOS]) were made following standard methodology (standard CUS) and repeated adjusting for foot size using shims (with-shim CUS). Areal bone mineral density (BMD) and estimated volumetric bone density (BMAD) at the spine, femoral neck, and whole body were determined using the Lunar DPX-IQ. African Americans had greater height- and weight-adjusted BUA than Caucasians, while Asians and African Americans had greater SOS than Caucasians and Latinas. Additionally, African Americans had greater height- and weight-adjusted BMD and BMAD than all other groups. CUS and DXA measurements correlated moderately (r = 0.2-0.5). With-shim CUS values were 0.9-7.8% lower than standard CUS values. In conclusion, African American women had greater DXA measurements than all others and greater CUS measurements than Caucasians. In contrast to DXA, CUS measurements in Asians and Latinas were not significantly lower than those in African Americans. Most notably, Asians had greater values for SOS than Caucasians and Latinas. Discrepancies in ethnic comparisons and modest correlations suggest that CUS and DXA methods may capture different bone qualities.

Two measures of physical activity as predictors of bone mass in a young cohort.

Objective:To compare the association of two measures of physical activity with bone mass in healthy children and young adults, as part of a larger study on bone mineral acquisition in youth. Design:Cross-sectional observation study. Setting:General community, outpatient study. Participants:Subjects included 103 non-Hispanic white female (n = 54) and male (n = 49) healthy volunteers aged 9 to 25 years. Main Outcome Measures:Self-reported physical activity was measured by a 3-day activity diary of all activities and a questionnaire designed to capture recreational activities throughout the year. Activity was expressed as hours per week of weight-bearing and non-weight-bearing activity. Bone mass at the hip, spine, and whole body was measured by dual x-ray absorptiometry. Results:The activity measures were not well correlated with each other. In males, weight-bearing and non-weight-bearing activity reported in 3-day diaries was positively associated with bone mass at the hip, spine, and whole body (p < 0.05). Among females, only weight-bearing activity measured by the yearly questionnaires was significantly positively associated with bone mass (p < 0.05). In males and females, weight-bearing activity was more highly correlated with bone mineral than was non-weight-bearing activity. In addition, the associations between activity and bone mass varied by skeletal site. Conclusions:The association between physical activity and bone mass varied both in direction and in significance depending on the physical activity instrument used. Gender differences were observed in the associations between specific activity instruments, type of activity (weight-bearing and non-weight-bearing), and bone mass at different skeletal sites. Variability associated with the two physical activity measures may contribute to discrepant findings in this study and in the literature.

Disparities in Obesity: Prevalence, Causes, and Solutions

ABSTRACT Obesity rates are rising in the United States; less obvious, but equally alarming, are the increased disparities in the rates. Rates of change for racial/ethnic minorities are significantly greater than those of whites, making it critical for those in the obesity field to better understand the differentially changing food and physical environments that are at the root of these recent trends. The solution to stemming the rising obesity epidemic must be a coordinated multi-level environmental approach, involving multiple solutions from various government, local community, school, health care, and other groups. Only then can disparities in obesity be reduced.