A Cross-sectional Data Analysis between Serum Total Bilirubin and Potential Obesity Indices in US Adults

Obesity is a major risk factor for metabolic and cardiovascular disorders. Recently, emerging biomarkers, such as the Visceral Adiposity Index (VAI) and Lipid Accumulation Product (LAP), have garnered attention for their utility in assessing visceral obesity. Bilirubin, a potent endogenous antioxidant, has been associated with protective effects against various diseases. This study aims to investigate the relationship between serum total bilirubin (STB) levels and VAI/LAP in adults.

This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) collected between 2003 and 2020. The calculation of VAI and LAP was performed computationally. Weighted multivariate regression models were used to explore the potential correlation between STB levels and VAI or LAP. RCS curves were used to identify the potential non-linear relationship. Moreover, subgroup analyses were conducted to examine heterogeneity across different populations.

The analysis included a cohort of 10,625 individuals aged 20 to 85 years. Both unadjusted and adjusted statistical models revealed a significant negative association between STB levels and VAI or LAP (all P< 0.001). RCS indicates that these relationships are linear. Subgroup analyses identified particularly strong associations in non-smokers aged 20-59 without hypertension/diabetes (P < 0.05).

Our study's strengths include the use of nationally representative data with appropriate weighting, comprehensive adjustment for confounding variables, and pioneering research on the link between serum bilirubin levels and visceral fat indices, which may indicate early metabolic risk markers. This finding highlights the significant role of bilirubin in body fat distribution and lipid metabolism.

This study revealed that STB was associated with VAI or LAP among the specific general American population aged 20-59 without hypertension/diabetes. Further prospective investigations are warranted to clarify the temporal relationship between STB and novel obesity indices.