Age and gender as risk factors for hyponatremia and hypernatremia.

BACKGROUND: This study assesses gender and age as independent risk factors for hypo- and hypernatremia and describes the prevalence of hypo- and hypernatremia in different population groups.

METHODS: Details of all serum Na results with accompanying patient demographics for 2 years were downloaded from the laboratory database into Microsoft Access for multiple logistic regression analysis using SPSS. Female gender and age <30 years were the reference groups.

RESULTS: Data from 303577 samples on 120137 patients were available for analysis. Prevalence at initial presentation to a health care provider of Na<136, <116, >145, and >165 mmol/l were for acute hospital care patients: 28.2%, 0.49%, 1.43%, and 0.06%; ambulatory hospital care: 21%, 0.17%, 0.53%, and 0.01%; community care: 7.2%, 0.03%, 0.72%, and <0.01%. Age odds ratios rose with increasing age to 1.89 and 8.70 (Na<136 and <116 mmol/l) and 7.09 and 24.39 (Na>145 and >165 mmol/l, respectively) for age >81 years. Male gender was a mild risk factor for Na<136 mmol/l and was otherwise unimportant.

CONCLUSIONS: Hyponatremia is a common but generally mild condition while hypernatremia is uncommon. Increasing age is a strong independent risk factor for both hypo- and hypernatremia. Gender is not an important risk factor for disturbances of serum Na concentration.