BMI has been a widely used standard measure to evaluate obesity-related health risk for many years. It does not, however, measure fat distribution, particularly abdominal fat, which is more directly associated with chronic disease and mortality. In 2020, a consensus statement suggested BMI-specific WC cut points in an attempt to further stratify risk. The purpose of this study was to determine whether the use of these WC cut points in BMI categories would enhance prediction of 10- and 20-year mortality risks.
The analysis used data from 139,213 postmenopausal women 50 to 79 years old, sampled between 1993 and 1998, with follow-up through 2021. Patients were split into a development cohort (n = 67,774) and two external validation cohorts:
• Validation Cohort 2 (n = 23,104), with women from varied and geographically remote U.S. centers
Height, weight, and waist circumference were assessed at recruitment. Participants were stratified into five BMI groups:
• Normal weight (18.5–<25 kg/m²)
• Overweight (25–<30 kg/m²)
• Obesity-1 (30–<35 kg/m²)
• Obesity-2 (35–<40 kg/m²)
• Obesity-3 (≥40 kg/m²)
Each of the BMI groups was also stratified according to WC cutpoints:
≥80 cm for normal weight,
≥90 cm for overweight,
≥105 cm for obesity-1,
≥115 cm for obesity-2 and 3.
Key findings
• During a median follow-up of 24 years, 69,297 women died.
• Normal BMI but increased WC: HR = 1.17 (95% CI, 1.12–1.21)
• Overweight with increased WC: HR = 1.19 (CI, 1.15–1.24)
• These risks were comparable to women with obesity-1 and normal WC: HR = 1.12 (CI, 1.08–1.16)
• Obesity-1 with increased WC: HR = 1.45 (CI, 1.35–1.55)
• This risk was comparable with those with obesity-3 and normal WC: HR = 1.40 (CI, 1.28–1.54)
• For Validation Cohort 1, WC addition increased c-statistics by 0.7% (from baseline to 61.3%) and continuous NRI by 20.4% (CI, 17.3–23.6%) at 10 years.
• For Validation Cohort 2, there was a 12.3% improvement in risk stratification (CI, 8.5–16.0%) but no consistent improvement in discrimination.
• The results at 20 years were comparable to those at 10 years, suggesting long-term applicability of these measures.
In this big cohort of postmenopausal women, categorizing BMI by waist circumference thresholds modestly enhanced prediction of mortality risk, especially for women with greater abdominal fat. These data argue in favor of routine incorporation of waist circumference into assessment of obesity and cardiovascular risk in older women.
Reference:
Aragaki, A. K., Manson, J. E., LeBlanc, E. S., Chlebowski, R. T., Tinker, L. F., Allison, M. A., Haring, B., Odegaard, A. O., Wassertheil-Smoller, S., Saquib, N., Masaki, K., Harris, H. R., Jager, L. R., Bea, J. W., Wactawski-Wende, J., & Anderson, G. L. (2025). Development and validation of body mass index-specific waist circumference thresholds in postmenopausal women : A prospective cohort study: A prospective cohort study. Annals of Internal Medicine, ANNALS-24-00713. https://doi.org/10.7326/ANNALS-24-00713
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