The association between atherogenic index of plasma (AIP) and ultrasound attenuation parameter (UAP) in Chinese adults: a cross-sectional study

This study aimed to investigate the association between the atherogenic index of plasma (AIP) and the ultrasound attenuation parameter (UAP) in Chinese adults. A cross-sectional study was conducted among 6141 physical examinees. Demographic, anthropometric, biochemical, and FibroTouch data were collected. AIP was calculated as Log10(triglyceride (TG)/high-density lipoprotein cholesterol (HDL)). Linear and logistic regression, restricted cubic spline (RCS), Receiver operating characteristic (ROC) curves, E-value, IDI, and NRI analyses were performed with multivariable adjustment. Sex-stratified sensitivity analysis was conducted to address gender imbalance. The mean age was 47.9 ± 10.2 years (94.1% male), and NAFLD prevalence (UAP ≥ 244 dB/m) was 71.7%. AIP was linearly and positively associated with UAP (p < 0.001); each 1-unit AIP increase correlated with a 23.03 dB/m UAP elevation (95% CI 18.38–27.68). Elevated AIP was strongly associated with NAFLD (OR = 5.62, 95% CI 3.00–10.52). RCS confirmed linear dose–response relationships (both p for non-linearity > 0.05). The AUC of AIP for NAFLD was 72.22%, superior to TC (70.63%) and HDL (68.45%); IDI/NRI further validated its better predictive capacity. E-value analysis indicated robustness against unmeasured confounding. Among Chinese adults, AIP has a significant linear correlation with NAFLD and UAP. AIP can serve as an independent correlated marker for NAFLD, and its discriminatory efficacy is superior to that of traditional lipid markers.