How well does the body adiposity index capture adiposity change in midlife women?: The SWAN fat patterning study

摘要

Objectives: The body adiposity index (BAI) is a proposed alternative to the body mass index (BMI) that has shown good cross-sectional agreement with percent body fat (%BF) in validation studies. The objective of this study was to examine the ability of BAI to track adiposity change over time in a biracial sample of midlife women. Methods: African-American (n = 159) and Caucasian (n = 206) women, aged 42-60 years, at the Chicago site of the Study of Women's Health Across the Nation were followed from 2002 to 2008. BAI and BMI were calculated from measurements taken at annual assessments. %BF was quantified using whole-body dual-energy X-ray absorptiometry. Difference scores (BAI Δ, BMI Δ, and %BF Δ) quantified adiposity change over a mean of 1.6 (SD = 0.7) years. Lin's concordance correlation (ρ c) and Bland-Altman limits-of-agreement assessed agreement between BAI and %BF. Results: In examining adiposity change, BAI Δ showed poor agreement with %BF Δ in the overall sample (ρ c = 0.41), African-American women (ρ c = 0.36), and Caucasian women (ρ c = 0.43). BAI Δ estimated %BF Δ with minimal bias (+0.4%) but low precision (±6.3%BF limits-of-agreement). %BF Δ had weaker correlations with BAI Δ (rs = 0.38-0.48) than with BMI Δ (rs = 0.48-0.59). BAI and BMI showed similar cross-sectional associations with %BF in the overall sample and within each race (rs 0.74). Conclusions: We conclude that BAI is less accurate than BMI in tracking adiposity change in midlife women, and would not be a suitable replacement for BMI in most research applications involving adiposity change.