Barriers to hydration and dietary sodium reduction for kidney stone prevention: a population-based study with 12-month clinical outcomes

Background: The global burden of kidney stone disease is increasing, with prevention reliant on achieving high urine volume and reducing dietary sodium. However, real-world adherence and its behavioral, environmental, and occupational drivers remain poorly understood, with limited studies validating self-reported behaviors against 24-h urine biomarkers. Methods: = 872) validated self-reported adherence against urine volume (≥2.5 L/day) and urinary sodium (≤100 mmol/day). Outcomes were adherence and symptomatic recurrence at 12 months; model performance was summarized using C-statistics and calibration indices. Multivariable logistic models identified predictors of adherence and recurrence. Results: Among 1,723 participants, adherence was 56.5% for hydration, 3.0% for sodium, and 1.2% for both; mean urine volume was 2.3 L/day and sodium excretion 178.4 mmol/day (≈10.3 g/day salt). Self-report showed high accuracy (hydration: sensitivity 87.2%, specificity 91.7%; sodium: sensitivity 78.6%, specificity 95.3%); prior counseling, higher knowledge, and greater self-efficacy increased adherence, while access/affordability barriers reduced it (C-statistics: 0.698 hydration, 0.784 sodium, 0.843 composite). Hydration adherence was lower with night shift (OR 0.67), rotating shifts (OR 0.58), limited workplace water (OR 0.52), and restricted bathrooms (OR 0.64), but higher at ambient temperature >25 °C (OR 1.67). At 12 months, recurrence was 18.1% (312/1,668); hydration (OR 0.68) and sodium adherence (OR 0.31) were protective, as were higher urine volume (OR 0.54 per L) and citrate (OR 0.93 per 100 mg/day), whereas higher urinary sodium (OR 1.42 per 50 mmol/day), calcium (OR 1.15 per 50 mg/day), and ambient temperature (OR 1.19 per 5 °C) increased risk; the recurrence model C-statistic was 0.723. Conclusions: Sodium restriction adherence is low, hydration moderate, biomarkers validate behaviors. Counseling, knowledge, self-efficacy, urban residence are associated with adherence; barriers impede it. Integrated interventions with monitoring and support may help reduce recurrence.