Hyponatremia predicts mortality after stroke

Background: Hyponatremia, the commonest electrolyte imbalance encountered in clinical practice, is associated with adverse outcomes. Despite this, understanding of the association between hyponatremia and stroke mortality outcome is limited. Aims: To investigate the association between admission serum sodium and mortality at various time-points after stroke. Methods: Cases of acute stroke admitted to Norfolk and Norwich University Hospital consecutively from January 2003 until June 2013 were included, with mortality outcomes ascertained until the end of December 2013. Odds ratios (OR) or Hazards ratio (HR) for death were constructed for various time points (within 7 days, 8-30 days, within 1 year and over full follow-up). Results: 8540 participants were included (47.4% male, mean age 77.3 (± 12.0) years). Point prevalence of hypernatremia and hyponatremia were 3.3% and 13.8%, respectively. In fully adjusted models controlling for age, sex, pre-stroke modified Rankin score, stroke type, Oxford community stroke project class and laboratory biochemical and hematological results, the ORs (up to one year)/HRs (for full follow up) for the above time points were 1.00, 1.11, 1.03, 1.05 for mild hyponatremia, 1.97, 0.78, 1.11, 1.2 for moderate hyponatremia, 3.31, 1.57, 2.45, 1.67 for severe hyponatremia and 0.47, 1.23, 1.30, 1.10 for hypernatremia. When stratified by age-groups, outcomes were poorer in younger hyponatremic patients (aged <75 years). Conclusions: Hyponatremia is prevalent in acute stroke admissions and is independently associated with higher mortality in patients