Low Sodium Raises Risk of Fracture

Compared with individuals without hyponatremia, those with chronic hyponatremia had a 4-fold increased odds of osteoporosis and 4.6- fold increased odds of fragility fracture.
Compared with individuals without hyponatremia, those with chronic hyponatremia had a 4-fold increased odds of osteoporosis and 4.6- fold increased odds of fragility fracture.
Hyponatremia is a risk factor for osteoporosis and fracture, a new study confirms. 

For the study, researchers matched 30,517 osteoporosis cases to 30,517 controls without osteoporosis and matched 46,256 fragility fracture cases to 46,256 controls without fragility fracture. Compared with individuals without hyponatremia, those with chronic hyponatremia had a 4-fold increased odds of osteoporosis and 4.6- fold increased odds of fragility fracture, according to a report published online ahead of print in The Journal of Clinical Endocrinology and Metabolism. Patients with recent hyponatremia had a 3-fold increased odds of both osteoporosis and fragility fracture. Patients with both chronic and recent hyponatremia had a 12- and 11-fold increased odds of osteoporosis and fragility fracture, respectively. 

The researchers defined recent hyponatremia as a serum sodium level below 135 mmol/L within 30 days before the end of the encounter window; they defined chronic hyponatremia as at least 2 consecutive serum sodium measurements below 135 mmol/L at least 1 year apart during the encounter window. 

Results also showed that lower serum sodium is associated with higher risk. For example, a median level of 130–134 mmol/L is associated with a 4.4-fold increased odds of osteoporosis and a 4.5-fold increased odds of fragility fracture, whereas a median level below 130 mmol/L is associated with a 6.6-fold and 7.0-fold increased odds of osteoporosis and fragility fracture, respectively. 

Women made up 66.3% of the osteoporosis cases and controls and 55.4% of the fragility fracture cases and controls. 

“This investigation adds to the accumulating evidence that even mild hyponatremia may have clinical implications for patients risk of osteoporosis and fragility fracture,” the researchers, led by Joseph G. Verbalis, MD, of Georgetown University Medical Center in Washington, D.C., wrote. 

Dr. Verbalis' group noted that their study potentially clarifies and expands the findings of the Rotterdam study, which found that hyponatremia at study entry was associated with a 1.4- fold increase in nonvertebral fractures over 7.4 years of follow-up and a 1.8- fold increase in prevalent, but not incident, vertebral or hip fractures.

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