title: Hyponatraemia at hospital admission is a predictor of overall mortality.
abstract: BACKGROUND
  Hyponatraemia is a prognostic marker of increased mortality and morbidity in selected groups of hospitalised patients. The aim of the present study was to examine the prevalence and prognostic significance of hyponatraemia at hospital admission in an unselected population with a broad spectrum of medical and surgical diagnoses.
  
  
  METHODS
  Consecutive patients >40 years of age admitted to a general district hospital in Greater Copenhagen between 1 April 1998 and 31 March 1999. Median follow-up time was 5.16 years (range 0-4372 days). Plasma sodium measurements were available in 2960 patients, and hyponatraemia defined as P-Na(+) <137 mmol/L at hospital admission was present in 1105 (37.3 %) patients.
  
  
  RESULTS
  One-year mortality was higher for hyponatraemic patients than for normonatraemic patients: 27.5% versus 17.7%. Moreover, hyponatraemia was an independent predictor of short and long-term all-cause mortality after 1 year and after the entire observation period respectively: hazard ratio (HR) 1.6 (95 % confidence interval (CI) 1.4-1.9, P < 0.0001) and HR 1.4 (95 % CI 1.3-1.6, P < 0.0001). Patients with hyponatraemia had longer hospitalisations than patients with normonatraemia: 7.6 (±0.38) days vs 5.6 (±0.21) days, P < 0.001. There was no interaction between hyponatraemia at admission and any admission diagnoses (P > 0.05 for all interaction analyses).
  
  
  CONCLUSIONS
  Hyponatraemia is associated with increased all-cause mortality and longer admission length independently of diagnosis and clinical variables.
authors.affiliation: Department of Cardiology, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark.
authors.forename: L
authors.initials: L
authors.lastname: Balling
authors.forename: F
authors.initials: F
authors.lastname: Gustafsson
authors.forename: J P
authors.initials: JP
authors.lastname: Goetze
authors.forename: M
authors.initials: M
authors.lastname: Dalsgaard
authors.forename: H
authors.initials: H
authors.lastname: Nielsen
authors.forename: S
authors.initials: S
authors.lastname: Boesgaard
authors.forename: M
authors.initials: M
authors.lastname: Bay
authors.forename: V
authors.initials: V
authors.lastname: Kirk
authors.forename: O W
authors.initials: OW
authors.lastname: Nielsen
authors.forename: L
authors.initials: L
authors.lastname: Køber
authors.forename: K
authors.initials: K
authors.lastname: Iversen
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization / Q000706:statistics & numerical data*; D006779:Hospitals, Public; D006801:Humans; D007010:Hyponatremia / Q000097:blood* / Q000401:mortality*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010343:Patient Admission; D011237:Predictive Value of Tests; D012016:Reference Values; D018570:Risk Assessment; D012720:Severity of Illness Index; D016019:Survival Analysis; D014505:Urban Population
keywords: all-cause mortality; electrolyte disturbance; hyponatraemia