Introduction: Lower socioeconomic status (SES) is associated with higher stone burden at presentation, requiring more frequent and invasive procedures. Unhealthy dietary patterns and impaired access to healthy food in low-income communities are thought to exacerbate this problem. To investigate whether the relationship between SES, diet and stone disease is reflected in 24-hour urine composition, we investigated the associations between 24-hour urine parameters and median income by home zip code in stone patients. Methods: The Registry for Stones of the Kidney and Ureter was queried for all adult subjects who underwent a 24-hour urine test between 2015 and 2022. A similar number of subjects who were prospectively followed but did not complete 24-hour urine testing were also evaluated. Demographic data including home zip code and clinical characteristics were abstracted for analysis. We then used publicly available zip-code level data from the U.S. Census Bureau to stratify patients into quintiles by median income and 24-hour urine parameters were compared. A multivariable linear regression model was created to identify significant independent predictors among demographic and past medical history characteristics. Results: Of 1,224 subjects who met inclusion criteria, 635 (52%) had undergone 24-hour urine testing. Compared to those in the top quintile, individuals in the bottom quintile of income were younger, more likely to be non-white and had a higher proportion of diabetes (16% vs 9%, p = 0.014), chronic kidney disease (6.2% vs 2.4%, p = 0.038) and chronic obstructive pulmonary disease (5% vs 1.6%, p = 0.036). These patients were also less likely to have 24-hour urine testing (42% versus 52%, p = 0.004). On comparison of 24-hour urine data, individuals in the bottom quintile of income had higher mean urinary sodium and on multivariable linear regression controlling for demographic and clinical characteristics, lower income remained significantly associated with increased urinary sodium (ß = 5.2 ± 2.3, p = 0.025). Conclusions: Lower SES is associated with higher levels of urinary sodium. In addition to reinforcing the need for more epidemiologic investigation and public health intervention, this finding highlights SES as a consideration for tailoring dietary modifications. SOURCE OF Funding: none
