**Background:** Kidney stones are a common urologic disease with increasing prevalence, placing substantial clinical and economic burdens on healthcare systems. Sarcopenia, defined as progressive loss of skeletal muscle mass and function, shares several pathophysiological pathways with kidney stone formation, including obesity, insulin resistance, inflammation, and physical inactivity. However, no prior study had directly examined the association between sarcopenia and kidney stones.
**Methods:** This cross-sectional study analyzed data from the National Health and Nutrition Examination Survey (NHANES) across seven cycles from 2011 to 2018. From an initial pool of 39,156 participants, 9,472 adults aged ≥20 years were included after applying exclusion criteria (age <20 years, missing kidney stone or sarcopenia data, missing covariate data). Sarcopenia was assessed using the sarcopenia index, calculated as total appendicular skeletal muscle mass (kg) divided by BMI (kg/m²), measured by dual-energy X-ray absorptiometry (DEXA). Sarcopenia was defined as a sarcopenia index <0.789 for men and <0.512 for women. Kidney stone history was self-reported. Covariates included age (<40/≥40 years), gender, race, education, marital status, BMI, hypertension, smoking, alcohol use, physical activity, blood urea nitrogen, creatinine, and uric acid. Multiple logistic regression models were constructed with progressive adjustment: Model 1 (univariate), Model 2 (gender, age, race), Model 3 (plus education, marital status, BMI), and Model 4 (plus hypertension, smoking, alcohol, physical activity, blood urea nitrogen, creatinine, uric acid). Restricted cubic spline (RCS) regression was used to assess dose–response relationships. Propensity score matching (PSM) was performed to address confounding.
**Key Results:** Among 9,472 participants, 759 (8.0%) reported a history of kidney stones and 811 (8.6%) met criteria for sarcopenia. Stone formers were more likely to be aged ≥40 years (63.8% vs. 48.1%, p<0.001), non-Hispanic white (49.1% vs. 35.1%, p<0.001), married (53.2% vs. 48.4%, p=0.011), have BMI ≥30 (47.2% vs. 36.1%, p<0.001), have hypertension (36.6% vs. 22.3%, p<0.001), and be current smokers (26.6% vs. 22.1%, p<0.001). Sarcopenia was more prevalent in stone formers (12.6% vs. 8.2%, p<0.001). Before PSM, logistic regression in Model 4 (fully adjusted) showed sarcopenia was significantly associated with kidney stones in all participants (aOR 1.286, 95% CI: 1.006–1.643, p=0.044) and those <40 years (aOR 1.697, 95% CI: 1.065–2.702, p=0.026), but not in those ≥40 years (aOR 0.965, 95% CI: 0.700–1.330, p=0.827). After PSM, the association became significant across all age groups in Model 4: all participants (aOR 2.365, 95% CI: 1.598–3.500, p<0.001), age <40 years (aOR 6.793, 95% CI: 2.619–17.618, p<0.001), and age ≥40 years (aOR 1.771, 95% CI: 1.138–2.757, p=0.011). RCS analysis demonstrated a non-linear inverse dose–response relationship between sarcopenia index and kidney stone prevalence, with lower sarcopenia index (indicating greater sarcopenia) associated with higher kidney stone risk.
**Clinical Implications:** This study provides the first evidence that sarcopenia is independently associated with increased odds of kidney stones in the U.S. adult population, particularly among younger adults (<40 years). The association persisted after rigorous adjustment for confounders and propensity score matching. Shared pathophysiological mechanisms—including obesity-induced inflammation, insulin resistance promoting muscle catabolism, and physical inactivity—may underlie this relationship. These findings suggest that sarcopenia assessment could help identify individuals at elevated risk for kidney stones, and that interventions targeting muscle mass preservation (e.g., resistance training, adequate protein intake) might have dual benefits for both sarcopenia and kidney stone prevention. However, as a cross-sectional study, causality cannot be established, and the study did not account for stone composition, size, or location. Prospective studies are needed to confirm these findings and explore underlying mechanisms.