Serum small dense LDL cholesterol is inversely associated with kidney stone prevalence: evidence from two independent cross-sectional studies.

This study investigated the association between serum small dense low-density lipoprotein cholesterol (sdLDL-C) levels and kidney stone formation in adults using two independent datasets. A hospital-based cross-sectional cohort included 757 participants (229 stone cases and 528 controls) from March 2022 to September 2025, with clinical data on blood biochemical markers and histories of hypertension and diabetes collected for analysis. Between-group comparisons were conducted using chi-square or Kruskal-Wallis tests, and the association between sdLDL-C and kidney stones was examined through multivariable logistic regression, subgroup analyzes. To evaluate the robustness and generalizability of the findings, data from 9,721 adults in the 2007-2016 National Health and Nutrition Examination Survey (NHANES) were also analyzed. In the Chinese cohort, higher sdLDL-C concentrations were independently associated with a lower risk of kidney stones (OR = 0.53, 95% CI: 0.38-0.74), with a non-linear inverse dose-response pattern. The NHANES cohort showed similar results, revealing a negative and linear association between sdLDL-C and stone risk (OR = 0.68, 95% CI: 0.50-0.91). Subgroup analyzes indicated that the protective association was most evident among individuals over 40 years and in both sexes in the Chinese cohort, whereas in NHANES it was more pronounced among participants aged 20-39 or 60-85 years and among females. These findings suggest that sdLDL-C is inversely associated with kidney stone risk across populations; however, prospective studies are required to determine causality.