A new study is complicating the long-standing use of body mass index as a measure of health in older adults, finding that waist circumference may offer a more reliable signal of early death risk than the widely used BMI formula.

The research, published Aug. 19 in the Journal of the American Geriatrics Society, found that among adults 65 and older, having a larger waist circumference was linked to a higher risk of early death. But being classified as overweight by BMI was, counterintuitively, associated with a lower risk of early death in the same population — a seemingly contradictory finding that has prompted closer examination from medical experts.

Researchers analyzed data from nearly 7,000 adults age 65 and older who were tracked as part of a large, nationally representative study funded by the U.S. National Institutes of Health. Participants were followed for up to 14 years, allowing scientists to examine how changes in BMI and waist circumference correlated with mortality risk over time.

Compared with men whose BMI fell in the normal range, men classified as overweight, with a BMI between 25 and 29.9, had a 46% lower risk of death. Men with class I or II obesity, defined as a BMI between 30 and just under 40, also showed a lower risk of death relative to the normal-BMI group.

Among women, those classified as overweight had a 27% lower risk of death compared with those in the normal BMI range. However, class I or II obesity was not associated with a statistically significant difference in mortality risk for women, and for both men and women with class III obesity, defined as a BMI of 40 or higher, there was no statistically significant difference in mortality risk compared with the normal-BMI group.

The pattern shifted........

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