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.

Keywords: Comorbidity; Electrolytes; Epidemiology and outcomes; General population; Hyponatremia; Medications; Mortality; NHANES; Outpatient.

Copyright © 2013 Elsevier Inc. All rights reserved.

Figures

Figure 1

Distribution of serum sodium concentrations (corrected for dilutional hyponatremia) (Please note y axis extends from 0% to 20%)

Figure 2

Prevalence of hyponatremia by age and gender by weighted analysis in NHANES 1999-2004

Figure 3

Odds Ratio for hyponatremia in various subgroups on logarithmic scale (95% confidence interval). Values reported in Table 1.

Figure 4

Cumulative mortality in subjects with normonatremia and hyponatremia(Please note y axis extends from 0% to 20%) (1mmol/L = 1mEq/L for Na)

Figure 5

Restricted cubic spline depicting relationship between corrected serum sodium and all-cause mortality. Dashed lines represent the 95% confidence interval.

Figure 6

Hazard ratio associated with hyponatremia in patients with various comorbidities on logarithmic scale. (95% confidence interval). Confidence interval and p values reported in Table 4.