Body roundness index and mental health in middle-aged and elderly adults: a prospective cohort study.

The global rise in mental disorders presents a significant public health challenge, highlighting the need for a deeper understanding of their underlying risk factors. Existing studies on obesity and brain health primarily rely on metrics such as body mass index and waist-to-hip ratio, which inadequately capture central obesity, a fat distribution strongly associated with increased health risks. This underscores the need for more precise metrics, with the body roundness index (BRI) emerging as a promising option. 321,596 UK Biobank participants were analyzed in this study. Cox regression models assessed associations between BRI and incident mental disorders, while logistic and multiple linear regression models explored relationships with psychiatric symptoms and white matter integrity, respectively. Results indicated that higher BRI was significantly associated with increased risks of incident overall mental disorders (HR [95% CI] = 1.12 [1.09, 1.15]), as well as specific high-prevalence disorders including substance use disorder (1.05 [1.01, 1.11]), depressive disorder (1.34 [1.24, 1.45]), and anxiety disorder (1.09 [1.03, 1.15]). An overall positive association was also observed between elevated BRI and adverse psychiatric symptoms and reduced white matter integrity. These findings highlighted BRI as a potential indicator of mental health. BRI's association with clinical and subclinical psychiatric outcomes emphasized its relevance in understanding the interplay between central adiposity and brain health.