A comparison of DXA and CT based methods for estimating the strength of the femoral neck in post-menopausal women.

UNLABELLED: The study goal was to compare simple two-dimensional (2D) analyses of bone strength using dual energy x-ray absorptiometry (DXA) data to more sophisticated three-dimensional (3D) finite element analyses using quantitative computed tomography (QCT) data. DXA- and QCT-derived femoral neck geometry, simple strength indices, and strength estimates were well correlated. INTRODUCTION: Simple 2D analyses of bone strength can be done with DXA data and applied to large data sets. We compared 2D analyses to 3D finite element analyses (FEA) based on QCT data. METHODS: Two hundred thirteen women participating in the Study of Women's Health Across the Nation (SWAN) received hip DXA and QCT scans. DXA BMD and femoral neck diameter and axis length were used to estimate geometry for composite bending (BSI) and compressive strength (CSI) indices. These and comparable indices computed by Hip Structure Analysis (HSA) on the same DXA data were compared to indices using QCT geometry. Simple 2D engineering simulations of a fall impacting on the greater trochanter were generated using HSA and QCT femoral neck geometry; these estimates were benchmarked to a 3D FEA of fall impact. RESULTS: DXA-derived CSI and BSI computed from BMD and by HSA correlated well with each other (R=0.92 and 0.70) and with QCT-derived indices (R=0.83-0.85 and 0.65-0.72). The 2D strength estimate using HSA geometry correlated well with that from QCT (R=0.76) and with the 3D FEA estimate (R=0.56). CONCLUSIONS: Femoral neck geometry computed by HSA from DXA data corresponds well enough to that from QCT for an analysis of load stress in the larger SWAN data set. Geometry derived from BMD data performed nearly as well. Proximal femur breaking strength estimated from 2D DXA data is not as well correlated with that derived by a 3D FEA using QCT data.

Menopausal bone changes and incident fractures in diabetic women: a cohort study.

SUMMARY: The purpose of this study was to evaluate the rate of bone loss and incident fractures in women with diabetes mellitus (DM) across menopause. During menopause, DM women experienced bone mineral density (BMD) loss that was faster at hip and slower at spine and had a higher risk of fractures, perhaps because of their earlier menopause. The increasing DM epidemic will contribute to higher fracture burden. INTRODUCTION: Women with DM have a higher risk of fractures independent of age, body mass index (BMI), and BMD. Our objective is to evaluate if women with DM experience greater bone loss and more fractures across menopause. METHODS: Two thousand one hundred seventy one women, aged 42 to 52 years at baseline (1996), enrolled in the Study of Women's Health Across the Nation (SWAN), a prospective study, with 8 years of annual follow up. One thousand three hundred forty six (62%) completed annual visit 7 (2004). Women with baseline fasting blood glucose level of ≥126 mg/dl and those being treated for diabetes were designated as DM. Annual assessment of menopausal stage, BMD, and urinary N-telopeptide (NTx) were carried out. Rate of change in BMD across menopause and annual self-report data for risk of incident fractures by DM status were determined. RESULTS: Despite higher baseline BMD at hip (p = <0.001), and lumbar spine (p = <0.001), rate of decline in BMD was faster at hip (ß = -0.45 vs. -0.11 gm/cm(2)/year, p = <0.001) for DM women, compared to non-DM. However, lumbar spine bone loss was slower in women with DM as compared to non-DM women (ß = 0.04 vs. -0.25 gm/cm(2)/year, p = 0.004). DM women experienced menopause 3 years earlier than non-DM women (p = 0.002), and age adjusted incident fractures were two fold higher in women with DM compared to non-DM (RR = 2.20, 95% CI: 1.26-3.85, p = <0.006). CONCLUSIONS: BMD loss is greater in hip and slower at spine in DM women during menopausal transition. Women with DM have a higher risk of fractures, perhaps because of their earlier menopause.

Education eclipses ethnicity in predicting the development of the metabolic syndrome in different ethnic groups in midlife: the Study of Women's Health Across the Nation (SWAN).

OBJECTIVE: To determine the respective roles of socio-economic status (SES) and ethnicity in the risk of incident metabolic syndrome in middle-aged women. DESIGN AND PARTICIPANTS: A total of 3302 pre- and peri-menopausal women, not receiving hormone therapy at baseline, took part in the Study of Women's Health Across the Nation, a multi-site, community-based, longitudinal study of the menopausal transition. The main outcome measures were to ascertain the prevalence of the metabolic syndrome and the incidence of the metabolic syndrome over 5 years of follow-up. RESULTS: At baseline, the prevalence of the metabolic syndrome was 21% (n = 673). Among 2512 women without metabolic syndrome at baseline, 12.8% (n = 321) developed the metabolic syndrome during 5 years of follow-up. Both ethnicity and SES were significant univariate predictors of incident metabolic syndrome. In multivariate logistic regression models that included age at baseline, menopausal status and site, baseline smoking and alcohol consumption at follow-up visit 1, as well as baseline values of each of the components of the metabolic syndrome, only education was an independent predictor of incident metabolic syndrome. CONCLUSION: Approximately 13% of peri-menopausal women developed the metabolic syndrome during the 5-year follow-up period. Education, but not ethnicity, was an independent predictor of incident metabolic syndrome risk.

Small angle X-ray scattering study on bovine porphobilinogen synthase (5-aminolaevulinate dehydratase).

The quaternary structure of the native (zinc) porphobilinogen synthase (5-amino-laevulinate dehydratase) from bovine liver and its lead-substituted derivative is studied in solution by small angle X-ray scattering. In spite of the profound inhibitory effect of lead ions in the enzyme they do not produce a change in the quaternary structure detectable by small angle X-ray scattering. The most important molecular parameters of the native enzyme were found to be: radius of gyration Rg = 4.04 +/- 0.04 nm and maximum dimension Dmax = 12.0 +/- 0.5 nm. The corresponding values for the lead derivative are: Rg = 4.26 +/- 0.1 nm and Dmax = 12.5 +/- 0.5 nm. The quaternary structure of the enzyme in solution is described by a model, which fits the experimental scattering and distance distribution function.