Study suggests obesity paradox for those over 80 due to non-cardiovascular disease mortality

A team of researchers affiliated with multiple institutions in China and the U.S. has found that the obesity paradox for those over 80 is driven mostly by non-cardiovascular disease mortality rates. In their paper published in the journal Nature Aging, the group describes their study of 20 years' worth of health-related data for several thousand older people living in China and what they learned from it. Jean Woo, with the Chinese University of Hong Kong, has published a News & Views piece outlining the history behind the use of the body mass index (BMI) and the work done by the researchers in this new effort, in the same journal issue.

For many years, people around the world have been told that in order to live a healthy life, they need to keep their BMI below 25. But as Woo notes, the BMI was created using data from younger people. In recent years, an obesity paradox has emerged for people older than 65—those with a higher-than-recommended BMI live longer than those who have adhered to the standard. In this new effort, the researchers found evidence that suggests this paradox is driven mostly by decreased non-cardiovascular mortality rates.

The work by the team involved analyzing health-related data collected from 27,026 older people (mean age approximately 93 years old) living in China over the years 1998 to 2018. Included in that data was the BMI of each individual as they grew older, the age at which they died and the cause.

The researchers found evidence of the obesity paradox—those people over 80 who had a BMI in the overweight to slightly obese range lived the longest. But they also found that it was mostly due to non-cardiovascular mortality rates. Such people tended to live longer if they had a respiratory disease or even cancer. Even those who were clearly obese tended to live longer than those who were under the BMI guidelines. The researchers also found a very slight increase in longevity for those with cardiovascular disease, but suggest it was negligible.

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