Elsevier

The American Journal of Medicine

Volume 126, Issue 12, December 2013, Pages 1127-1137.e1
The American Journal of Medicine

Clinical research study
Prevalence of Hyponatremia and Association with Mortality: Results from NHANES

Preliminary analysis was presented at: the American Society of Nephrology annual meeting, October 30 to November 4, 2012, San Diego, California.
https://doi.org/10.1016/j.amjmed.2013.07.021Get rights and content

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.

Section snippets

Materials and Methods

The National Health and Nutrition Examination Survey (NHANES) is conducted by the National Center for Health Statistics. Since 1999, data have been collected continuously from a representative sample of the civilian non-institutionalized population of the United States via in-home personal interviews and physical examinations in mobile examination centers, including laboratory measurements of serum electrolytes, creatinine, protein, and lipids.25 NHANES uses a complex, multistage probability

Results

Overall, 31,116 subjects were surveyed during the continuous NHANES cycles between 1999 and 2004. Our analysis included 14,804 subjects aged 18 years or more who had a measured serum sodium concentration. Hyponatremia was defined as serum sodium below the reference ranges provided by the NHANES laboratory testing centers, which were 133 to 145 mmol/L for the 1999-2002 survey cycles and 136 to 144 mmol/L for 2003-2004.27, 28, 29 Subjects with hypernatremia were excluded (n = 88), as were 19

Discussion

We report, for the first time, an estimate of the prevalence of hyponatremia in the general US population and its relative prevalence in subjects with and without specific comorbidities. Our analysis demonstrates an increase in the prevalence of hyponatremia with age and a higher prevalence of hyponatremia among women in the general population, a finding that was suspected given similar trends previously reported among cohorts of patients in acute and long-term care facilities, and a previously

Conclusions

After excluding cases of pseudohyponatremia and correcting for dilutional hyponatremia, our analysis of the NHANES 1999-2004 cohort estimates the overall prevalence of hyponatremia to be 1.72% of the US population. We demonstrate an increasing prevalence of hyponatremia with increasing age in the population, higher rates of hyponatremia among women, and a significant association between hyponatremia and all-cause mortality that persists even after adjustments for age, gender, and several

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    Funding: This work was supported in part by Health Resources and Services Administration Contract 234–2005-370011C and National Institute of Diabetes and Digestive and Kidney Diseases Grant T35 DK093430.

    Conflict of Interest: None.

    Authorship: All authors had access to the data and played a role in writing this manuscript.

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