Associations between novel anthropometric indices and cognitive function among U.S. older adults

Background Previous obesity indices have struggled to accurately account for the relationship between obesity and cognitive function, and the purpose of this study was to investigate the relationship between two novel anthropometric indices: A body size index (ABSI) and body roundness index (BRI), and cognitive function in an older population in the United States. Methods This study utilized data from the National Health and Nutrition Examination Survey (NHANES) 2011–2012 and 2013–2014. To evaluate cognitive function, three cognitive assessments were employed: the Consortium for the Establishment of an Alzheimer's Disease Registry (CERAD) test, the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST). Logistic regression analyses were further applied to investigate the association between ABSI/BRI and cognitive test scores, as well as with the odds of cognitive impairment (CI) prevalence, respectively. A smoothed fitting curve was also used to describe the nonlinear negative association between the above two novel anthropometric indices and cognitive function. Interaction tests and subgroup analyses were also performed. Results The study included 2639 older participants aged 60 years and older. After adjusting for confounding variables, our analyses revealed a statistically significant negative association between ABSI and BRI and cognitive function. Compared with individuals in the lowest quartile of the ABSI, individuals in the highest quartile had decreased CERAD scores (β = -0.69, 95% CI: -1.36, -0.03, p -value = 0.0401) and decreased DSST scores (β = -2.15, 95% CI: -3.58, -0.72, p -value = 0.0033). Individuals in the second quartile had decreased CERAD scores compared to individuals in the lowest quartile of BRI (β = -0.68, 95% CI: -1.35, -0.01, p -value = 0.0479). In addition, higher ABSI was significantly associated with a higher prevalence of CI, with an increased odds of CI prevalence in individuals in the highest quartile compared to individuals in the lowest quartile of ABSI (CERAD OR = 1.50, 95% CI: 1.01, 2.24, p -value < 0.0458; DSST OR = 1.68, 95% CI: 1.20, 2.33, p -value = 0.0093). Conclusions ABSI and BRI were strongly associated with cognitive decline among US. older adults. In addition, higher ABSI levels may be positively associated with the odds of CI prevalence.