Secular Trends and Prognostic Value of the Body Shape Index in U.S. Adults.

Abstract

Objective: A Body Shape Index (BSI), previously developed and evaluated as an improvement over traditional adiposity measures for predicting health risks, has not been comprehensively characterized with respect to its temporal trends, population disparities, and prognostic value in the United States.

Methods: This analysis examined data from 47,762 adults across 10 NHANES cycles (1999-2018). BSI trends were assessed across demographic and health-related subgroups. All-cause mortality risk was evaluated using Cox regression, with adjustment for multiple confounders. Interaction and restricted cubic spline analyses explored effect modification and nonlinearity.

Results: Mean BSI increased significantly over the two decades. Disparities persisted or widened over time. Elevated BSI was independently associated with higher mortality risk, particularly above the median, with a nonlinear escalation in risk at higher BSI levels. The impact of high BSI on all-cause mortality was stronger in males and varied by race/ethnicity, while lower BSI showed no protective effect.

Conclusions: BSI demonstrates a rising trend and persistent disparities among U.S. adults, with high BSI independently predicting adverse all-cause mortality in a nonlinear manner. These findings from the analyzed data supported the utility of BSI in risk stratification and highlighted the need for targeted interventions. Future research should explore BSI's role in public health strategies.