Hyponatremia and mortality among very elderly residents in a geriatric health service facility.

INTRODUCTION: Hyponatremia is common among elderly patients. This study aimed to examine the prognostic value of hyponatremia among elderly residents in a geriatric facility.

METHODS: We retrospectively examined the association between serum sodium levels and mortality among 118 residents (82% female, mean age 85.5 years) in a single geriatric health service facility. We defined hyponatremia as Na < 135 mEq/L. On the basis of single measurements of serum sodium at periodic examinations, the patients were divided into hyponatremia and non-hyponatremia groups. Multivariable Cox proportional hazards models were used to evaluate the effect of hyponatremia on mortality from May 2005 to April 2007.

RESULTS: Thirty-three patients (28%) had hyponatremia. Over a 1-year follow-up period, the cumulative survival rate was significantly lower in patients with hyponatremia than in those without hyponatremia. In a multivariate analysis, including traditional risk factors for death, hyponatremia was associated with an increased mortality risk (adjusted hazard ratio 2.73; 95% confidence interval 1.01-5.16; p = 0.047).

CONCLUSIONS: Hyponatremia is common and is a predictor of mortality in the near future among very elderly residents of a geriatric facility.