Hyponatremia Is Associated With Increased Osteoporosis and Bone Fractures in a Large US Health System Population

Context: The significance of studies suggesting an increased risk of bone fragility fractures with hyponatremia through mechanisms of induced bone loss and increased falls has not been demonstrated in large patient populations with different types of hyponatremia. Objective: This matched case-control study evaluated the effect of hyponatremia on osteoporosis and fragility fractures in a patient population of more than 2.9 million. Design, Setting, and Participants: Osteoporosis (n = 30 517) and fragility fracture (n = 46 256) cases from the MedStar Health database were matched on age, sex, race, and patient record length with controls without osteoporosis (n = 30 517) and without fragility fractures (n = 46 256), respectively. Cases without matched controls or serum sodium (Na+) data or with Na+ with a same-day blood glucose greater than 200 mg/dL were excluded. Main Outcome Measures: Incidence of diagnosis of osteoporosis and fragility fractures of the upper or lower extremity, pelvis, and vertebrae were the outcome measures. Results: Multivariate conditional logistic regression models demonstrated that hyponatremia was associated with osteoporosis and/or fragility fractures, including chronic [osteoporosis: odds ratio (OR) 3.97, 95% confidence interval (CI) 3.59–4.39; fracture: OR 4.61, 95% CI 4.15–5.11], recent (osteoporosis: OR 3.06, 95% CI 2.81–3.33; fracture: OR 3.05, 95% CI 2.83–3.29), and combined chronic and recent hyponatremia (osteoporosis: OR 12.09, 95% CI 9.34–15.66; fracture: OR 11.21, 95% CI 8.81–14.26). Odds of osteoporosis or fragility fracture increased incrementally with categorical decrease in median serum Na+. Conclusions: These analyses support the hypothesis that hyponatremia is a risk factor for osteoporosis and fracture. Additional studies are required to evaluate whether correction of hyponatremia will improve patient outcomes.