WHR Is a Better Predictor of All-Cause Mortality in Older Adults than BMI

Lead author Preethi Srikanthan, MD, from the University of Southern California, Los Angeles, said in a news release, "Basically, it isn't BMI that matters in older adults -- it's waist size.... Other studies have suggested that both waist size and BMI matter in young and middle-aged adults and that BMI may not be useful in older adults; this is one of the first studies to show that relative waist size does matter in older adults, even if BMI does not matter."

The goal of this study was to evaluate the association between 3 measures of obesity and all-cause mortality in a group of healthy older adults, using data from the MacArthur Successful Aging Study, a longitudinal study of high-functioning men and women aged 70 to 79 years at baseline. The association of BMI, waist circumference, and WHR with all-cause mortality risk was determined with use of proportional hazards regression to adjust for sex, race, age at baseline, and smoking status. The investigators tested for obesity interactions with sex, race, and smoking status and performed stratified analyses based on the results of interaction testing.

In both unadjusted and adjusted analyses, there was no association between all-cause mortality and BMI or waist circumference, whereas all-cause mortality increased with WHR. There was an interaction with sex, with a graded relationship between WHR and mortality in women (relative hazard, 1.28 per 0.1 increase in WHR; 95% confidence interval [CI], 1.05 - 1.55). In men, a threshold relationship was observed (relative hazard, 1.75 for WHR > 1.0 vs WHR ≤1.0; 95% CI, 1.06 - 2.91).

"WHR, rather than BMI or WC [waist circumference], appears to be the more appropriate yardstick for obesity-related risk stratification of high-functioning older adults, and possibly all older adults," the study authors write.

Limitations of this study include the possible underestimation of BMI because height and weight were self-reported. In addition, WHR, waist circumference, and BMI were based on single measurements.

The study authors concluded that, "Given our use of self-reported weight and height data, these findings need to be confirmed in other cohorts of older adults.... Further research into the mechanisms underlying the increased health risks associated with high WHR is also needed, specifically to delineate the role of intra-abdominal visceral fat, relative to pelvic bone size, gluteal muscle, and gluteal fat, in older adults' health risks."