SAN DIEGO—Hyponatremia is a relatively common electrolyte abnormality in the general U.S. adult population, and it is associated with an increased risk of death, according to data presented at Kidney Week 2012.

Using 1999-2004 data from the National Health and Nutrition Examination Survey, Sue Gu, a fourth-year medical student, and colleagues at Columbia University Medical Center in New York looked for the presence of hyponatremia, defined as a serum sodium level below 135 mEq/L, among individuals aged 18 years and older. The overall prevalence was 3.38%, and was significantly higher among men than women (4.32% vs. 2.37%). The prevalence increased with age. It was 2.82%, 3.32%, and 5.31% among individuals aged 18-44, 45-64, and 65 and older, the researchers found. This trend was found among men (1.75%, 2.63%, and 4.13%) and women (3.89%, 3.97%, and 6.19%). Gu’s team found that hyponatremia was associated with a significant 2.3 times increased risk of death in unadjusted analyses. The association remained significant in adjusted analyses.

“We see our results as particularly interesting, as this is the first known study to estimate the prevalence of hyponatremia in a general outpatient population,” Gu told Renal & Urology News. “While it was previously known that hyponatremia was associated with poor outcomes and mortality in hospitalized patients, we have found that it also portends a poor prognosis in the ambulatory setting as well.”

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In another study, researchers at the University of Texas Southwestern Medical Center in Dallas found that hyponatremia is associated with an increased risk of death in an ambulatory young and ethnically diverse population.

Fabrice Gankam Kengne, MD, and collaborators studied 3,551 individuals enrolled in the Dallas Heart Study. Subjects had a median age of 43 years. Hyponatremia was present in 6.9% of the cohort.

At the end of a median follow-up of 8.4 years, 202 deaths occurred, including 29 among individuals with hyponatremia (serum sodium level below 135 mEq/L). In unadjusted analyses, hyponatremia was associated with a twofold increased risk of death. After adjusting for age, gender, ethnicity, hypertension, dyslipidemia, diabetes, smoking, alcohol use, renal function and other potential confounders, hyponatremia was associated with a significant 75% increased risk of death.