Association between weight-adjusted waist index and C-reactive protein in adults: A population-based study

The weight-adjusted waist index (WWI) and C-reactive protein (CRP) have been independently associated with multiple chronic conditions. Given that central adiposity drives systemic inflammation, and WWI serves as a novel marker of central obesity, WWI may be associated with CRP levels. However, evidence on this relationship remains limited. This study aimed to explore the association between WWI and CRP in a nationally representative sample of US adults. This cross-sectional study included 8495 participants from the National Health and Nutrition Examination Survey. Weighted multiple regression and subgroup analyses were conducted to assess the association between WWI and CRP, adjusting for potential confounders. Generalized additive models and 2-piecewise linear regression were used to explore nonlinear relationships. After adjusting for potential confounders, a positive association was observed between WWI and CRP (β = 1.060, 95% confidence interval [CI] = 0.652-1.468). Subgroup analyses further revealed a significant positive association, particularly among participants with coronary heart disease (β = 4.357, 95% CI = 1.461-7.253), diabetes mellitus (β = 2.282, 95% CI = 1.031-3.532), or heavy drinking (β = 1.728, 95% CI = 0.758-2.698), as well as in non-Hispanic Black individuals (β = 1.650, 95% CI = 0.949-2.351). Nonlinear relationships were observed in current smokers and adults aged 20 to 60 years, with inflection points at 12.349 cm/√kg and 11.514 cm/√kg, respectively. The results indicate that higher WWI above the identified thresholds was associated with elevated CRP levels, particularly among current smokers and adults aged 20 to 60 years. These findings suggest that WWI may serve as a simple anthropometric indicator for identifying individuals with increased inflammatory risk. Further prospective studies are needed to validate these findings.