(ORDO NEWS) — Scientists from China conducted a large-scale analysis that showed that people over 80 years old with a body mass index above the current recommended norm have a lower mortality rate. The results obtained demonstrate the need to revise the weight recommendations for this age group.
BMI indicators are used to assess how much a person’s weight corresponds to the norm for his height. Most recommendations suggest that a person with a score above 25 is overweight, while those with a score above 30 are considered obese.
Xiaoming Shi of the Chinese Center for Disease Control and Prevention in Beijing and colleagues have studied the mortality risk of more than 27,000 people over 80 across China since 1998. The average age of people was 93 years old when they entered the study, then they were followed until 2018 or death (if earlier).
The team took into account several factors, including socioeconomic status, education, and whether the person smoked.
The BMI recommendations are based on measurements taken in younger age groups, Shi says. As the world’s population ages, it is important to ensure that these recommendations also make sense for older age groups, he said.
Previous analyzes have found a correlation between higher BMI scores in older age groups and lower mortality rates, but this is the first study to address the issue with such a large sample size.
Researchers have found that the optimal BMI for people over 80 is around 29. This is mainly due to a lower risk of death from non-vascular causes such as cancer or respiratory disease.
In addition, this group had a low risk of death from cardiovascular disease, although this relationship was weaker. Even those with a BMI in the obese range of 30 to 35 had a lower mortality rate than those with a BMI in the 20 to 25 range.
As Shi points out, it’s not clear why a higher BMI is associated with a lower mortality rate. He suggested that this could be explained by the fact that such people have a more nutritious diet.
He also notes that, in general, the BMI rates in this population were lower than in the West. More than 40 percent of people over 60 in the US are obese. “Our results most likely cannot be extrapolated to other age and ethnic groups,” he clarifies.
“This study highlights the importance of considering age when considering the association between BMI and mortality or other health risks,” explains Louise Baur of the University of Sydney.
She says the study is unable to say exactly why being overweight might be associated with better health in people over 80. The researcher agrees that this can be explained by good nutrition.
“While BMI is an accessible and inexpensive way to assess a person’s health status, it should not be relied upon as the sole measure of health,” adds Nicholas Fuller, also from the University of Sydney.
BMI is based on body weight, but a person’s disease risk is related to body fat, not weight. It’s more important to focus on metrics that tell us more about body fat and where it’s distributed like around the waist to better understand health status and risks.”
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