Associations of the body roundness index with cognitive function in US older adults and the mediating role of depression: a cross-sectional study from the NHANES 2011–2014

The body roundness index (BRI) accurately assesses body composition and visceral fat distribution, but its independent associations with cognitive function and cognitive impairment remain unclear. This study, which is based on data from the 2011-2014 U.S. National Health and Nutrition Examination Survey (NHANES), explores the associations between the BRI and cognitive function as well as cognitive impairment in older adults. Weighted linear regression and weighted logistic regression models were used for data analysis. Restricted cubic spline (RCS) models, subgroup analysis, and mediation analysis were conducted to explore effect modification, nonlinear associations, and the mediating role of depression. The BRI score was negatively correlated with the cognitive function score (DSST score β = -0.63, P = 0.037; Sum Score β = -0.83, P = 0.042) and was not significantly associated with cognitive impairment. As the BRI score increases, both the DSST score (trend P = 0.013) and the Sum Score (trend P = 0.023) show a linear decrease. The mediation effect analysis revealed that depression mediated 39.4% of the association between the BRI score and cognitive function, suggesting that the effect may be indirectly mediated through mental health pathways. Subgroup analysis and RCS models did not reveal significant interaction effects or nonlinear associations.