Association between hyponatremia and mortality in neurocritical patients with traumatic brain injury: A systematic review and meta-analysis.

Abstract

Traumatic brain injury (TBI) is a major global cause of death and disability. Hyponatremia is a frequent complication in neurocritical patients with TBI and has been associated with adverse clinical outcomes. However, the association between hyponatremia and mortality in patients with TBI remains uncertain and inconsistently reported. This systematic review and meta-analysis aimed to evaluate the association between hyponatremia and mortality compared with normonatremia in neurocritical patients with TBI and to estimate the incidence of mortality among patients with hyponatremia. PubMed, Scopus, and Web of Science were systematically searched through February 2026, complemented by searches in the Cochrane Central Register of Controlled Trials (CENTRAL), Clinical Trials registers, and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP). Observational studies evaluating the association between hyponatremia and mortality in adult patients with traumatic brain injury (TBI) were included. Pooled mortality proportions and pooled risk ratios (RRs) with 95% confidence intervals (CIs) were calculated using Der Simonian and Laird random-effects models. Subgroup analyses, sensitivity analyses, meta-regressions, and publication bias assessments were also performed. Eighteen studies were included in the systematic review and fourteen in the meta-analysis, comprising 6439 adult patients with traumatic brain injury. The overall mortality incidence among patients with hyponatremia was 11% (95% CI: 7-15%). Hyponatremia was not associated with increased mortality compared with normonatremia (RR: 1.06; 95% CI: 0.80-1.39). Subgroup analyses according to study design and timing of sodium assessment showed consistent findings without significant differences. Age, sex, and ICU length of stay did not significantly influence these associations. No significant publication bias was detected. Hyponatremia was not associated with increased mortality compared with normonatremia. Early monitoring of serum sodium concentrations may be of clinical interest in neurocritical TBI care, although the prognostic significance of hyponatremia should be interpreted with caution given the heterogeneity and observational nature of the available evidence.