Age and gender as risk factors for hyponatremia and hypernatremia

Abstract

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 303,577 samples on 120,137 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.

Introduction

There is little agreement on the prevalence of disturbances of sodium balance or on the importance of gender and age as markers of risk. Previous estimates of hyponatremia of 0.2–29.8% [1], [2] and hypernatremia of 0.3–8.9% [3], [4] have varied with the differences in the definitions of the disturbance and the population surveyed. Most studies on hyponatremia have examined elderly and/or psychiatric populations with particular emphasis on psychotropic medications as a cause of hyponatremia [5], [6]. Little has been published on the comparative prevalence of hypo- and hypernatremia in different patient populations (hospital or community). Female gender has been suggested as a risk factor for psychotropic [7], diuretic [8], and exercise-induced [9] hyponatremia. While some studies show increasing age to be a risk factor [7], others show no association with age [8], [10]. This study assesses gender and age as independent risk factors for hypo- and hypernatremia in a mixed community/hospital population and describes the prevalence of different levels of dysnatremia (hyponatremia and hypernatremia) in different population groups.