Association between the Zhejiang University index and kidney stone risks in US adults: evidence from NHANES 2007-2018.

BACKGROUND: Kidney stones carry a substantial population health burden and are demonstrated to be increasingly associated with metabolic dysregulation. We examined whether the Zhejiang University (ZJU) index, a composite metabolic parameter derived from routine clinical data, is associated with kidney stone history in US adults. METHODS: We used National Health and Nutrition Examination Survey (NHANES) 2007-2018 to assess the association between the ZJU index and self-report kidney stone history among adults aged 20 years or older. We applied survey-weighted logistic regression models to examine the relationship between the ZJU index and kidney stone history. Non-linearity was assessed using flexible spline and segmented regression. Discrimination was evaluated using receiver operating characteristic analysis. RESULTS: Among the 25,605 participants analyzed, 2,484 (9.7%) reported a history of kidney stones. Prevalence increased across ZJU index quartiles, from 4.09% in quartile 1 to 16.90% in quartile 4. In fully adjusted models, higher ZJU index was associated with higher odds of kidney stones (odds ratio 1.210, 95% CI: 1.186-1.234), with evidence of non-linearity and a turning point at 38.1. The ZJU index showed favorable discrimination (area under the curve 0.819) and an empirically derived threshold of 36.78 (sensitivity 76.2%, specificity 71.5%). CONCLUSION: Higher ZJU index was positively associated with kidney stone history in a nationally representative US sample, supporting its potential application in population-level risk stratification and prevention-oriented public health planning.