The correlation of hip fracture and hyponatremia in the elderly

Increasing age is considered one of the risk factors for hyponatremia. The concept of asymptomatic hyponatremia is not correct anymore as these patients have a greater risk for falls, bone fractures and attention impairment. The combination of old age and a fall is a common recipe for admission to a nursing home.

We identified 249 patients 65 years of age or older who were admitted to hospital with the diagnosis of hip fracture secondary to fall, during a 3-year period. We compared their serum Na level on admission with that of controls: 44 ambulatory patients admitted for elective hip or knee replacement surgery during the same time frame. Odds ratios (ORs) were calculated using logistic regression.

The prevalence of hyponatremia in cases was 16.9%, versus 4.6% in controls (p=0.03). Age and hyponatremia were strongly correlated with hip fracture secondary to fall. The univariate OR for hip fracture associated with each 10-year increase in age was 5.57 (p<0.0001). After controlling for age, cases were almost 5 times as likely as controls to be hyponatremic (OR=4.80, p=0.04).

Even mild hyponatremia in the elderly should be considered a risk factor for falls. Correction of hyponatremia in the elderly may reduce morbidity and mortality, and at the same time, it has a huge impact on socioeconomic status.