Characteristics and outcome of acute medical admissions with hyponatremia: even mild hyponatremia is associated with higher mortality.

Hyponatremia is a common finding in hospitalized patients. In this retrospective cohort study we assessed the characteristics and outcome of acute medical admissions with hyponatremia. Compared to the normal sodium group, those with hyponatremia were significantly older and the Charlson Comorbidity Index (CCI) was higher. The number of admissions to MCU/ICU between both groups was similar, but hyponatremic patients had a longer length of stay and both 28-day and one-year mortality were higher, even in patients with mild hyponatremia. Hyponatremia was independently associated with mortality after adjustment for age, CCI and polypharmacy, as was found in the subgroup with mild hyponatremia.