As the global population ages, understanding the relationship between body composition and mortality becomes increasingly important for public health strategies. A recent study with results published in the European Heart Journal conducted among the oldest-old individuals in China explored this complex relationship, examining the impact of body mass index (BMI) and waist circumference (WC) on all-cause and cause-specific mortality.
The study enrolled 5306 participants with a mean baseline age of 90.6 years. Participants were categorized based on BMI and WC measurements, and mortality outcomes were analyzed, taking into account various factors such as age, sex, smoking status, chronic diseases, and cognitive impairment.
Higher BMI was inversely associated with all-cause mortality among the oldest-old, with each 1 kg/m2 increase in BMI correlating with a decrease in mortality risk. This inverse association extended to cause-specific mortality, including cardiovascular disease (CVD) and non-CVD mortality, indicating a protective effect of higher BMI across different causes of death.
Utilizing Mendelian randomization (MR) analysis, the study delved into causal relationships between genetically predicted BMI and mortality. The findings revealed a significant causal relationship, with each 1 kg/m2 increase in genetically predicted BMI linked to a decrease in all-cause mortality risk.
While observational analyses pointed to an inverse association between WC and all-cause mortality, MR analysis uncovered a positive causal relationship, suggesting that higher WC was associated with increased mortality risk. This disparity underscores the importance of considering both observational and causal analyses to gain a comprehensive understanding of the relationship between body composition and mortality.
Subgroup analyses further highlighted the nuanced relationship between BMI, WC, and mortality. Participants with worse functional status, cognitive impairment, chronic diseases, or ADL disability exhibited more pronounced inverse causal effects of BMI on mortality, emphasizing the differential impact of body composition across diverse subpopulations. Participants with higher BMI and lower WC demonstrated the lowest mortality risk, suggesting that a combination of higher BMI and lower WC may confer protective effects against mortality among the oldest-old.
The study's findings have significant implications for public health interventions targeting the oldest-old population. They underscore the complexity of the relationship between body composition and mortality, emphasizing the need for tailored approaches that consider individual characteristics and risk factors. Future research could explore the underlying mechanisms driving these associations and investigate potential interventions to optimize body composition and reduce mortality risk among older adults.
Sources: European Heart Journal
