The correlation of hip fracture and hyponatremia in the elderly.

Background: 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.

Methods: 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.

Results: 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).

Conclusions: 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.