title: Prevalence of hyponatremia and association with mortality: results from NHANES.
abstract: BACKGROUND
  Hyponatremia is the most common electrolyte abnormality in hospitalized patients and is associated with adverse outcomes, but its prevalence and significance in the general US population is unknown. Our aims were to determine the prevalence of hyponatremia and its association with mortality in the population.
  
  
  METHODS
  We performed a population-based, cross-sectional study of 14,697 adults aged ≥ 18 years who participated in the nationally representative National Health and Nutrition Examination Survey for 1999-2004. By using measurements of serum sodium corrected for dilutional effect of hyperglycemia, we determined the association of hyponatremia with patient characteristics, comorbidities, and prescription medications, and performed unadjusted and adjusted Cox proportional hazards regression to find the association of hyponatremia with all-cause mortality.
  
  
  RESULTS
  We provide the first estimate of the prevalence of hyponatremia in the US population, which in our weighted analysis was 1.72%. Prevalence of hyponatremia was significantly higher in women (2.09%, P = .004) and increased with age. Hyponatremia was more common in subjects with hypertension, diabetes, coronary artery disease, stroke, chronic obstructive pulmonary disease, cancer, and psychiatric disorders, and less common in those with no comorbidities (1.04%, P < .001). There was a significant risk of death associated with hyponatremia in unadjusted (hazard ratio [HR], 3.61; P < .001) and adjusted Cox models controlling for demographics, smoking, comorbidities, and insurance status (HR, 2.43; P < .001). There was a U-shaped relationship between serum sodium and HR for mortality.
  
  
  CONCLUSIONS
  Our findings suggest that hyponatremia is a predictor of mortality in the general population independently of age, gender, and comorbid conditions.
authors.affiliation: Division of Nephrology, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY. Electronic address: sm2206@columbia.edu.
authors.forename: Sumit
authors.initials: S
authors.lastname: Mohan
authors.forename: Sue
authors.initials: S
authors.lastname: Gu
authors.forename: Amay
authors.initials: A
authors.lastname: Parikh
authors.forename: Jai
authors.initials: J
authors.lastname: Radhakrishnan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000453:epidemiology* / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D016016:Proportional Hazards Models; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Comorbidity; Electrolytes; Epidemiology and outcomes; General population; Hyponatremia; Medications; Mortality; NHANES; Outpatient