Hyponatremia at the time of hospital admission is associated with an increased risk of death and longer in-patient stays, according to a new study.

Louise Balling, MD, of the Department of Cardiology, Rigshospitalet, University of Copenhagen, Denmark, and colleagues studied 2,960 patients older than 40 years who were admitted to a hospital in Greater Copenhagen. 

Hyponatremia, defined as a plasma sodium level below 137 mmol/L at hospital admission, was present in 1,105 patients (37.3%). Patients had a median follow-up period of 5.16 years.

The 1-year mortality rate was higher for patients with hyponatremia than in those with normonatremia (27.55 vs. 17.7%), the researchers reported online ahead of print in the Internal Medicine Journal.

Hyponatremia independently predicted a significant 60% and 40% increased risk of short- and long-term all-cause mortality after 1 year and after the entire observation period, respectively, according to the investigators.

Patients with hyponatremia had a hospital stay of 7.6 days compared with 5.6 days for those with normonatremia, a significant difference between the groups.