Association between lipid accumulation product and visceral adiposity index and rheumatoid arthritis: NHANES 1999–2018

While the Lipid Accumulation Product (LAP) and Visceral Adiposity Index (VAI) offer improved assessment of visceral fat distribution compared to traditional measures, their connection with rheumatoid arthritis (RA) has not been thoroughly explored. This research aimed to assess the links between LAP, VAI, and RA occurrence using nationally representative datasets. This cross-sectional study analyzed information from the National Health and Nutrition Examination Survey (NHANES) covering the years 1999–2018. RA status was determined based on self-reported physician diagnosis. Sex-specific formulas were employed to calculate LAP and VAI. Statistical techniques included weighted multivariable logistic regression with three progressive models, restricted cubic spline (RCS) analysis, piecewise linear regression, and subgroup analyses. The study comprised 15,918 individuals, including 1,988 RA cases and 13,930 non-RA controls. RA patients demonstrated distinct demographic and clinical profiles compared to non-RA participants, exhibiting older age, greater female representation, reduced educational attainment (P = 0.03), and elevated frequencies of smoking, hypertension, and diabetes (all P < 0.001). Both LAP and VAI measurements were markedly elevated in the RA group (P < 0.001). After comprehensive covariate adjustment, LAP maintained a significant association with RA prevalence (OR = 1.002, P < 0.001). Individuals in the highest LAP tertile displayed 41.0% greater RA prevalence (OR = 1.410, P < 0.001), demonstrating a clear dose-response pattern (P for trend < 0.001). RCS analysis identified a significant nonlinear LAP-RA relationship (P for nonlinearity < 0.001), with a threshold effect at LAP = 43.45. Below this value, the association was notably stronger (OR = 1.0028, P < 0.001), whereas above it the relationship plateaued (P = 0.096). In contrast, VAI exhibited no significant association with RA (P for overall = 0.397) or nonlinear pattern (P for nonlinearity = 0.864). Stratified analyses revealed that hypertension status significantly modified the LAP-RA association (P for interaction = 0.040), with hypertensive individuals showing more pronounced effects. Borderline age-related differences were also noted, with stronger associations among younger participants (< 60 years) and in non-Hispanic White and non-Hispanic Black subgroups. This research indicates a potential link between LAP and RA occurrence, possibly highlighting the influence of abdominal fat deposition in RA development. Being an easily obtainable indicator that solely necessitates waist measurement and triglyceride assessment, LAP could function as an efficient preliminary screening method for identifying RA susceptibility in general healthcare environments. Additionally, it might contribute valuable insights for developing preventive approaches targeting metabolic factors in RA management. Not applicable.