Race/ethnic differences in associations between bone mineral density and fracture history in older men.

SUMMARY: To determine whether there are race/ethnic differences in bone mineral density (BMD) by fracture history in men aged 65 years and older, we performed cross-sectional analysis in five large independent cohorts. Low BMD was associated with a higher prevalence of fracture in all cohorts, and the magnitude of the BMD differences by fracture status was similar across groups. INTRODUCTION: We aimed to determine whether there are race/ethnic and geographic differences in bone mineral density by fracture history in men aged 65 years and older. METHOD: The datasets included the Osteoporotic Fractures in Men (MrOS) Study (5,342 White, 243 African-American, 190 Asian, and 126 Hispanic), MrOS Hong Kong (1,968 Hong Kong Chinese), Tobago Bone Health Study (641 Afro-Caribbean), Namwon Study (1,834 Korean), and Dong-gu Study (2,057 Korean). The two Korean cohorts were combined. RESULTS: The prevalence of self-reported non-traumatic fracture was US white, 17.1 %; Afro-Caribbean, 5.5 %; US African-American, 15.1 %; US Hispanic, 13.7 %; US Asian, 10.5 %; Hong Kong Chinese, 5.6 %, and Korean, 5.1 %. The mean differences in hip and lumbar spine BMD between subjects with fracture and without fracture were statistically significant in all cohorts except US African American and US Asian men. There was a significant race/ethnic interaction for lumbar spine BMD by fracture status (p for interaction = 0.02), which was driven by the small number of Hispanic men. There was no interaction for femoral neck or total hip BMD. There were no significant race/ethnic differences in the odds ratio of fracture by BMD. CONCLUSIONS: Low BMD was associated with a higher prevalence of fracture in all cohorts and the magnitude of the BMD differences by fracture status was similar across groups suggesting homogeneity in the BMD-fracture relationship among older men.

The association of serum 25-hydroxyvitamin D with indicators of bone quality in men of Caucasian and African ancestry.

UNLABELLED: We examined the association of serum 25-hydroxyvitamin D [25(OH)D] with indices of bone quality in older men. Positive associations for 25(OH)D and bone mineral density, content, cortical thickness, and axial and polar strength strain indices were observed among Caucasians; however, among men of African descent findings were either null or negative. INTRODUCTION: There are limited data on serum 25(OH)D and bone measures in men of African ancestry. To better understand racial differences in vitamin D status and bone health, a cross-sectional study among 446 Caucasian men in the US and 496 men of African ancestry in Tobago (age ≥ 65 years) was conducted. METHODS: Serum 25(OH)D (liquid chromatography and tandem mass spectrometry) was measured, and peripheral quantitative computed tomography scans were administered. Bone measures estimated included trabecular and cortical volumetric bone mineral density (vBMD), bone mineral content (BMC), bone geometry (cross-sectional area and cortical thickness), and polar and axial strength strain indices (SSIp and SSIx). RESULTS: Men of African ancestry had higher 25(OH)D than Caucasians (34.7 vs. 27.6 ng/ml, p < 0.01). Among Caucasians, 25(OH)D was positively (p trend < 0.05) associated with cortical vBMD, total BMC, cortical thickness, SSIp, and SSIx at the distal radius after adjustment for potential confounders. Similar patterns were observed at the distal tibia. In contrast, in men of African ancestry, there was an inverse association (p trend < 0.05) between 25(OH)D and the cross-sectional area, and SSIx. Race modified (p for interaction < 0.05) the association between 25(OH)D and total BMC, cross-sectional area, SSIp, SSIx, and trabecular vBMD of the radius. In men of African ancestry, there was evidence of a threshold effect (at approximately 18 ng/ml) for 25(OH)D on tibial total BMC and cortical thickness. CONCLUSIONS: More studies are needed to better comprehend these race differences for 25(OH)D and bone density, geometry, and indices of bone strength.

Association of body composition and physical activity with proximal femur geometry in middle-aged and elderly Afro-Caribbean men: the Tobago bone health study.

Osteoporotic fractures are less prevalent in African Americans than in caucasians, possibly because of differences in bone structural strength. Bone structural adaptation can be attributed to changes in load, crudely measured as lean and fat mass throughout life. The purpose of this analysis was to describe the associations of leg lean mass, total body fat mass, and hours walked per week with femoral bone mineral density (BMD) and bone geometry in a cross-sectional sample of 1,748 men of African descent between the ages of 40 and 79 years. BMD, section modulus (Z), cross-sectional area (CSA), and subperiosteal width were measured from dual energy X-ray absortiometry (DXA) scans using the hip structural analysis (HSA) program. Multiple linear regression models explained 35% to 48% of the variance in bending (Z) and axial (CSA) strength at the femoral neck and shaft. Independent of all covariates including total body fat mass, one standard deviation increase in leg lean mass was significantly associated with a 5% to 8% higher Z, CSA, and BMD (P < 0.010) at the neck and shaft. The number of hours walked per week was not a strong or consistent independent predictor of bone geometry or BMD. We have shown that weight is the strongest independent predictor of femur BMD and geometric strength although the effect appears to be mediated by lean mass since leg lean mass fraction and total body fat mass fraction had significant and opposing effects at the narrow neck and shaft in this group of middle aged and elderly men.

The relation of endogenous sex steroid hormone concentrations to serum lipid and lipoprotein levels in postmenopausal women.

The relation of concentrations of endogenous estrogens and androgens to lipid and lipoprotein levels was examined in 176 white, postmenopausal women (mean age, 58 years) with an average of 9 years since the onset of menopause. All of the women were participants in a clinical trial of the effect of walking on postmenopausal bone loss. In that trial, women were randomized into either a walking group or a control group and were followed for 3 years. There were no differences in the serum hormones or lipids by randomized group, and hence, results from this study are presented for both groups combined. None of the women were on estrogen replacement therapy. Data were available from year 1 (1982-1983) of the trial for the estrogens, lipids, and lipoproteins. Information on androgens was available for 143 of these women. Hormone levels were determined by highly specific methods involving extraction, column chromatography, and radioimmunoassay. About 50% of the women had estradiol levels at or below the sensitivity level (2.5 pg/ml) of the assay; therefore, estradiol levels were viewed as dichotomous (measurable/not measurable), and the estradiol results should be interpreted with caution. There was little relation of the androgens to the lipid values. Univariate analyses suggested a direct relation between total cholesterol, low density lipoprotein cholesterol, and triglyceride levels with estradiol. An inverse relation was suggested between serum estrone and estradiol and total high density lipoprotein (HDL) cholesterol and HDL2 cholesterol, although none of these associations were statistically significant. Multiple regression analyses revealed that the primary determinant of the HDL cholesterol and triglyceride levels was the degree of obesity as estimated by the body mass index (weight (kg)/height (m)2). Addition of estrone or estradiol to the models did not contribute to the prediction of lipid levels. These results do not support the hypothesis of there being a relation between endogenous sex hormone levels and lipid levels in postmenopausal women. The results suggest that sex hormones cannot explain the sex difference in lipid levels and may not contribute to the rise in coronary heart disease that occurs in women around menopause.

Cigarette smoking and serum sex hormones in men.

The relation between cigarette smoking and serum sex hormone concentrations was examined in two samples of the Multiple Risk Factor Intervention Trial (MRFIT) population. One sample consisted of 121 men at the Pittsburgh, Pennsylvania MRFIT center who were followed longitudinally for four years. The other sample was drawn from the entire MRFIT cohort and consisted of 163 MRFIT participants who subsequently developed coronary heart disease and 163 matched controls. The results indicated a positive correlation between cigarette smoking and serum total androstenedione concentration. The association was independent of age, relative weight, alcohol drinking, blood pressure, and high density lipoprotein (HDL) cholesterol. Serum total and free testosterone concentrations were positively correlated with cigarette smoking among the longitudinal sample and the controls, but not for the baseline sera from the coronary heart disease cases. This positive correlation was also independent of age, relative weight, alcohol drinking, blood pressure, and HDL cholesterol. There was no association between either serum estradiol or estrone concentrations and cigarette smoking in this population. These observations may have important implications for epidemiologic studies of diseases with significant smoking relations.

The assessment of historical physical activity and its relation to adult bone parameters.

The aim of the present research was to determine the association between historical physical activity and baseline bone measurements in a group of 223 postmenopausal women participating in a clinical trial in Pittsburgh, Pennsylvania, from 1981 to 1986 by evaluating the effect of moderate physical activity on bone loss. Historical physical activity was assessed by a survey which divided the life span into four time periods (14-21, 22-34, 35-50, and 50+ years) and inquired about participation in leisure time physical activities for each period. From the responses, kilocalories of energy expenditure were calculated. Cortical bone density and area were measured in the radius with a computerized tomography scanner. The historical physical activity survey was administered a second time two to three months after the initial test to a 10% random sample of the women in order to determine the test-retest reliability of the instrument. Since the measurements of historical physical activity proved to be reliable, estimates of kilocalories determined for the entire population of women were correlated with bone area and density. A significant relation was found to exist between historical physical activity and dimensions of adult bone, particularly bone area. This association remained significant after adjustment for potential confounding variables and seemed to be strongest in the earlier age periods. To the authors' knowledge, this is the first report of a significant association between historical physical activity and bone.