ZJU index and the prevalence of kidney stones in US adults: evidence from NHANES 2007-2018.

BACKGROUND

Kidney stones represent a prevalent urinary tract condition frequently observed in individuals with metabolic disturbances. The Zhejiang University (ZJU) Index, a composite metabolic indicator, has been proposed for metabolic evaluation; however, its connection with the occurrence of kidney stones has yet to be thoroughly investigated.

METHODS

This cross-sectional analysis utilized data from the 2007-2018 National Health and Nutrition Examination Survey (NHANES) to explore the association between the ZJU Index and kidney stone status. Multivariate logistic regression models were employed to estimate independent associations. Restricted cubic spline (RCS) and segmented regression methods were applied to characterize potential nonlinear trends. Robustness of findings was further examined through subgroup stratification and sensitivity procedures.

RESULTS

Among 14,593 participants, 1,401 reported a history of kidney stones. After adjustment for potential confounders, higher ZJU Index values were positively associated with kidney stone prevalence (odds ratio [OR] per 1-unit increase, 1.03; 95% confidence interval [CI], 1.03-1.04). Compared with the lowest quartile, the adjusted ORs for kidney stone prevalence were 1.45 (95% CI, 1.12-1.89), 1.75 (95% CI, 1.33-2.29), and 2.14 (95% CI, 1.62-2.82) across increasing ZJU Index quartiles (P for trend < 0.001). Restricted cubic spline analyses suggested a non-linear association, with a steeper increase at lower to moderate ZJU Index levels and attenuation of the association at higher levels. These associations were consistent across demographic subgroups and sensitivity analyses.

CONCLUSION

In U.S. adults, elevated ZJU index levels are nonlinearly and positively associated with the prevalence of kidney stones, suggesting that the ZJU index may serve as a potential metabolic indicator for assessing urolithiasis risk. Given the routine availability and accessibility of its component variables, the ZJU index holds promise as a valuable tool for epidemiological screening and metabolic risk management in populations at high risk for kidney stones.