Older women with larger waist circumference may be at much higher risk of death for any given BMI, according to an international study that followed women for more than two decades.

The study found that for postmenopausal women aged 50-79 years, considering waist circumference along with BMI better reflects the role of obesity in mortality risk than using BMI alone.

 The findings support recent recommendations by the International Atherosclerosis Society (IAS) and the International Chair in Cardiometabolic Risk (ICCR) to include waist circumference and BMI measurement in patient screening for high-risk obesity phenotypes. 

The results of the study are published in Annals of Internal Medicine.

Researchers from the Fred Hutchinson Cancer Center and colleagues analyzed data on 139,213 postmenopausal women aged 50 to 79 years in the Women's Health Initiative, a multicenter population-based study that enrolled participants from 1993 to 1998 and continued through 2021.

Participants were divided into three groups: the development group (67,774 participants), validation group 1 (48,335 participants with a high prevalence of overweight or obesity), and validation group 2 (23,104 participants from different geographically separate centers).

BMI categories included normal weight, overweight, and obesity grade 1 through 3 groups.

Nearly all obese-2 or obese-3 women had a waist circumference of 88 centimeters or greater, which is the current value for women and independent of BMI. The researchers found that mortality risk was higher for categories with a larger BMI and normal waist circumference.

In addition, mortality risk was similar for women with normal weight or overweight and large waist circumference and obese-1 women with normal waist circumference.