High BMI and low waist circumference positively impact the mortality in elderly: Study

A recent study published in the European Heart Journal highlighted the complexities of longevity among the oldest-old with emerging evidence that suggests a paradoxical relationship between body mass index (BMI), waist circumference (WC) and mortality.

This study from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) spanned for two decades and encompassed a total of 5306 individuals who were of 80 years and above. This research by Yuebin Lv and team looked into the causal associations between BMI, WC and mortality in the elderly population of China.

Contrary to traditional information which often associates lower BMI with better health outcomes, the findings of this study challenge this belief. The observational analyses revealed that higher BMI and WC were correlated with decreased mortality risk among the oldest-old, with each incremental increase linked with a significant reduction in mortality risk.

The most intriguing findings emerged from the Mendelian randomization models that provided insights into the causal link between genetic predispositions for BMI, WC and mortality. While genetically predicted increases in BMI were associated to lower mortality risk, the relationship with WC was notably different.

For every 1 kg/m² increase in genetically predicted BMI, there was a 4.5% decrease in all-cause mortality risk which suggested that a slightly higher BMI might be optimal for the oldest-old. Also, higher WC was causally associated with increased mortality risk from cardiovascular diseases (CVD) and non-CVD causes. The non-linear analyses of this study further highlighted the nature of these associations by indicating that the lowest mortality risk was observed at a BMI of around 28.0 kg/m² that reinforces the notion of an 'obesity paradox' among the elderly.

As the findings suggest, interventions focusing solely on reducing BMI may not be appropriate for this demographic. Instead, a more precise approach considering both BMI and WC with an emphasis on maintaining higher BMI levels alongside lower WC measurements for optimal longevity may be require. Overall, the findings of this research illuminate the need for a better understanding of obesity and its impact on health outcomes among the elderly population.

Source:

Lv, Y., Zhang, Y., Li, X., Gao, X., Ren, Y., Deng, L., Xu, L., Zhou, J., Wu, B., Wei, Y., Cui, X., Xu, Z., Guo, Y., Qiu, Y., Ye, L., Chen, C., Wang, J., Li, C., Luo, Y., … Shi, X. (2024). Body mass index, waist circumference, and mortality in subjects older than 80 years: a Mendelian randomization study. In European Heart Journal. Oxford University Press (OUP). https://doi.org/10.1093/eurheartj/ehae206