A bigger waist may increase the risk of dying for older women

Older women with larger waist circumference may be at a much greater risk of dying for any given BMI, according to international research, which monitored women over more than two decades. The study found that for post-menopausal women aged 50–79, taking waist circumference into account along with BMI, better reflected the role obesity plays in the risk of dying than using BMI alone.

A prospective cohort study found that stratifying BMI categories by BMI-specific waist circumference thresholds modestly improved mortality risk stratification in postmenopausal women, with larger waist circumference predicting greater mortality in women across BMI groups.

The findings support recent International Atherosclerosis Society (IAS) and International Chair on Cardiometabolic Risk (ICCR) recommendations to include waist circumference measurement with BMI in patient screenings to identify high-risk obesity phenotypes. The study is published in the Annals of Internal Medicine. An Editorial and Summary for Patients were also published in the same issue.

Researchers from the Fred Hutchinson Cancer Center and colleagues analyzed data for 139,213 postmenopausal women aged 50 to 79 years from the Women’s Health Initiative, a multicenter, population-based study with enrollment from 1993 to 1998 and follow-up through 2021. The participants were divided into three cohorts: development cohort (67,774 participants), Validation Cohort 1 (48,335 participants with a high prevalence of overweight or obesity), and Validation Cohort 2 (23,104 participants from diverse, geographically separate centers).

Researchers developed three models to predict mortality risk: a mortality model; the mortality model plus BMI (BMI model); and the mortality model plus BMI plus BMI-specific waist circumference thresholds (BMI-WC model). BMI categories included normal weight, overweight, and obesity classes 1 to 3, and were stratified by prespecified waist circumference thresholds of ≥80, ≥90, ≥105, ≥115, and ≥115 cm, respectively.

Validation Cohort 1 had a higher prevalence of large waist circumference (21.9%), according to BMI-specific waist thresholds, than Validation Cohort 2 (18.2%). Nearly all women with obesity-2 or obesity-3 had waist circumference of 88 cm or larger—the current guideline for women and independent of BMI.

After stratification, the researchers found that mortality risk was greater for BMI categories with larger waist circumference than their counterparts with normal waist circumference. Additionally, mortality risk was similar for women with normal weight or overweight and large waist circumference and women with obesity-1 and normal waist circumference.

Overall, stratifying BMI categories by waist circumference thresholds modestly improves risk stratification for all-cause mortality in healthy postmenopausal women with a high prevalence of overweight or obesity. These results suggest that clinical guidelines for assessing adiposity would benefit from the incorporation of waist circumference with BMI measures.