Fluid Intake and Kidney Function: A Systematic Review and Dose-Response Meta-analysis

INTRODUCTION: Fluid intake is widely recommended in clinical practice, yet evidence linking habitual fluid intake to kidney outcomes remains inconsistent. We evaluated dose-response associations between fluid intake volume and kidney function decline or prevalent advanced chronic kidney disease. METHODS: We searched EMBASE, PubMed, and the Cochrane Library through Feb 2025 for adult studies reporting total fluid intake, plain water intake, or urine volume in relation to eGFR decline or prevalent advanced-stage chronic kidney disease. Random-effects meta-regression and two-stage dose-response meta-analysis were used to assess linear and non-linear associations, with prespecified subgroup analyses by baseline kidney function. RESULTS: Sixteen studies including 70,053 participants were included. Higher total fluid intake was linearly associated with slower eGFR decline (p = 0.02; β = 0.97 mL/min/1.73 m²/year; 95% CI 0.15-1.79) and with lower odds of prevalent advanced-stage chronic kidney disease (p < 0.001; log-OR -0.27; 95% CI -0.43 to -0.11). In subgroup analyses, this association was observed in studies with mean baseline eGFR ≥60 mL/min/1.73 m² (p = 0.016), but not in studies with mean baseline eGFR <60 mL/min/1.73 m². Evidence for plain water intake and urine volume was limited. CONCLUSIONS: Higher daily total fluid intake, within the ranges studied, was associated with slower eGFR decline and lower odds of prevalent advanced CKD, particularly among studies with mean baseline eGFR ≥60 mL/min/1.73 m². Because the evidence was predominantly observational, these findings cannot establish that increasing fluid intake preserves kidney function. Future studies should distinguish plain water from other beverage categories and incorporate objective biomarkers of hydration and volume status. REGISTRATION: CRD42024627796.