Longitudinal patterns of abdominal visceral and subcutaneous adipose tissue, total body composition, and anthropometric measures in postmenopausal women: Results from the Women's Health Initiative.

BACKGROUND: Abdominal adiposity, including visceral and subcutaneous abdominal adipose tissue (VAT and SAT), is recognized as a strong risk factor for cardiometabolic disease, cancer, and mortality. OBJECTIVE: The primary aim of this analysis is to describe longitudinal patterns of change in abdominal adipose tissue in postmenopausal women, overall and stratified by age, race/ethnicity, and years since menopause. METHODS: The data are from six years of follow up on 10,184 postmenopausal women (7828 non-Hispanic White women, 1423 non-Hispanic Black women, and 703 Hispanic women) who participated in the Women's Health Initiative (WHI). The WHI is a large prospective cohort study of postmenopausal women across the United States. All participants in this analysis had DXA scans in the 1990s as part of the WHI protocol. Hologic APEX software was used to re-analyze archived DXA scans and obtain measures of abdominal adipose tissue. Analyses examined differences in abdominal adipose tissue, overall adiposity, and anthropometric variables. RESULTS: There were important differences in VAT and SAT by age and race/ethnicity. In women <60 years, VAT increased over the follow-up period, while in women ≥70 years, VAT decreased. Non-Hispanic Black women had the highest levels of SAT. Hispanic women had the highest VAT levels. Women more than ten years since menopause had less SAT and more VAT than women less than ten years since menopause, resulting in a higher VAT/SAT ratio. There was a moderate to strong correlation between measures of abdominal adipose tissue and anthropometric measurements of body size. Still, there were substantial differences in the quantity of VAT and SAT within BMI and waist circumference categories. CONCLUSIONS: These results demonstrate differences in VAT and SAT according to age, race/ethnicity, time since menopause, and compared to standard measures of body composition in a large and diverse cohort of postmenopausal women.

Confounders in the association between exercise and femur bone in postmenopausal women.

INTRODUCTION: Abundant animal and human evidence demonstrates that loading stimuli generate positive adaptive changes in bone, but effects of activity on bone mineral density (BMD) are often modest and frequently equivocal. HYPOTHESIS: Physical activity effects on the femur would be better reflected in measurements of geometry than BMD. STUDY DESIGN: Cross-sectional cohort study. METHODS: We used data from 6032 women of mixed ethnicity aged 50-79 yr who had dual-energy x-ray absorptiometry (DXA) scans of the total body and hip from the Women's Health Initiative observational study. Subjects were distributed in three ways: self-report categories included 1) tertiles of MET and 2) reported minutes per week walking for exercise. A third, more objective, category was based on tertile of lean body mass fraction (LMF) from DXA scans. Femur outcomes included conventional femoral neck and total hip BMD, bone mineral content and region area, and geometry measurements using the Hip Structure Analysis software. Outcomes were compared between activity groups using models adjusted for common confounders. RESULTS: Adjusted bone measurements showed similar activity effects with all three grouping variables, but these were greater and more significant when evaluated by LMF tertile. Women in the highest LMF tertile had the widest femurs. Differences in section modulus between highest and lowest tertile of LMF were 50%-80% greater than the association with bone mineral content and two to three times that on BMD. CONCLUSIONS: More active women in the Women's Health Initiative observational study had geometrically stronger femurs, although effects are underestimated, not apparent, or sometimes negative when using BMD as an outcome. CLINICAL RELEVANCE: Exercise improves the strength of the femur largely by adding bone to the outer cortical surface; this improves resistance to bending, but because of the way DXA measurements are made, this may paradoxically reduce BMD.