Association of hyponatremia and risk of in-hospital mortality in patients with acute stroke: a systematic review and meta-analysis

Objective Hyponatremia is among the most common electrolyte disturbances in acute stroke and has been increasingly recognized as a potential predictor of early complications. We aimed to evaluate whether hyponatremia on admission is associated with increased in-hospital mortality in patients with acute ischemic stroke (IS) and hemorrhagic stroke (HS). Methods We conducted a comprehensive systematic search of PubMed, Scopus, and Embase to identify relevant studies published between 1st January 2000 and 30th October 2025. Eligible studies included patients with acute stroke, reported admission serum sodium levels, and compared outcomes between hyponatremic and normonatremic groups. Pooled risk ratios (RRs) with 95% confidence intervals (CIs) were estimated using a random-effects model. Subgroup analyses were performed based on stroke type. Results Seventeen studies involving patients assessed within 24–72 h of stroke onset were included. Hyponatremia on admission was significantly associated with higher in-hospital mortality (RR 1.41, 95% CI 1.14–1.74). The association remained significant in ischemic stroke (RR 1.29, 95% CI 1.16–1.42) and in studies including mixed IS and HS populations (RR 1.59, 95% CI 1.19–2.12). No significant association was observed in hemorrhagic stroke alone (RR 1.47, 95% CI 0.70–3.10). Between-study heterogeneity was moderate ( I 2 = 58.9%, p < 0.001). Funnel plot assessment suggested no significant publication bias. Conclusions Hyponatremia on admission is associated with increased in-hospital mortality in acute stroke, particularly in ischemic stroke. Early identification and management of hyponatremia may have prognostic and therapeutic relevance in acute stroke care. Systematic Review Registration PROSPERO: CRD420251110001.