Nonlinear association between atherogenic index of plasma and chronic kidney disease: a nationwide cross-sectional study

Abstract Background: Chronic kidney disease (CKD) is a kind of chronic disease which endangers human health seriously. The relationship between chronic kidney disease and atherogenic index of plasma (AIP) has rarely been explored. The present study investigates the association between AIP and CKD. Methods: We utilized a weighted multivariate logistic regression model to rigorously assess the relationship between AIP and CKD, complemented by the generation of smooth curves to delineate the interplay between these variables. Upon discerning a non-linear relationship, we engaged a recursive partitioning algorithm in conjunction with a two-stage linear regression model to precisely determine the inflection point. Furthermore, stratified analyses were meticulously performed to dissect and elucidate the heterogeneity within population subgroups. Results：The study involved 23888 participants from the United States. Within the regression model that accounted for all covariates, the odds ratio (OR) correlating CKD with AIP was calculated at 1.12 (95% CI: 0.91, 1.36), suggesting no significant association between AIP levels and the prevalence of CKD. However, the results of the linear trend test suggested that the relationship between them may be non-linear. Smooth curve analysis confirmed the non-linear relationship between AIP and CKD, and identified an inflection point at -0.55. Below this threshold, AIP exhibited a significant inverse correlation with CKD. In contrast, beyond the inflection point, a pronounced positive correlation was detected. Further stratified analyses elucidated distinct patterns: a non-linear association between AIP and CKD was observed in female participants and those aged 50 and above, whereas a linear association was noted among male participants and those below the age of 50. Subgroup analyses, focusing on the interplay of BMI, alcohol consumption, and smoking status, disclosed significant variations within these demographic subsets. Conclusion：We found a curvilinear relationship between chronic kidney disease and atherogenic index of plasma.