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Nephrol Dial Transplant. 2016 Oct;31(10):1662-9. doi: 10.1093/ndt/gfw029. Epub 2016 Mar 23.

Mild prolonged chronic hyponatremia and risk of hip fracture in the elderly.

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Renal Consultants of Houston, Houston, TX, USA Nephrology Section, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.
Internal Medicine Research Unit, Internal Medicine Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.
Instituto de Investigaciones Metabólicas, Universidad del Salvador, Buenos Aires, Argentina.
Division of Nephrology, Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Division of Nephrology and Hypertension, University of California, Irvine, CA, USA Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
Nephrology Division, Massachusetts General Hospital, Boston, MA, USA.
Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA Departments of Epidemiology, Biostatistics and Medicine, University of California, San Francisco, San Francisco, CA, USA Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA, USA.



Hip fractures are among the most serious bone fractures in the elderly, producing significant morbidity and mortality. Several observational studies have found that mild hyponatremia can adversely affect bone, with fractures occurring as a potential complication. We examined if there is an independent association between prolonged chronic hyponatremia (>90 days duration) and risk of hip fracture in the elderly.


We performed a retrospective cohort study in adults >60 years of age from a prepaid health maintenance organization who had two or more measurements of plasma sodium between 2005 and 2012. The incidence of hip fractures was assessed in a very restrictive population: subjects with prolonged chronic hyponatremia, defined as plasma sodium values <135 mmol/L, lasting >90 days. Multivariable Cox regression was performed to determine the hazard ratio (HR) for hip fracture risk associated with prolonged chronic hyponatremia after adjustment for the propensity to have hyponatremia, fracture risk factors and relevant baseline characteristics.


Among 31 527 eligible patients, only 228 (0.9%) had prolonged chronic hyponatremia. Mean plasma sodium was 132 ± 5 mmol/L in hyponatremic patients and 139 ± 3 mmol/L in normonatremic patients (P < 0.001). The absolute risk for hip fracture was 7/282 in patients with prolonged chronic hyponatremia and 411/313 299 in normonatremic patients. Hyponatremic patients had a substantially elevated rate of hip fracture [adjusted HR 4.52 (95% CI 2.14-9.6)], which was even higher in those with moderate hyponatremia (<130 mmol/L) [adjusted HR 7.61 (95% CI 2.8-20.5)].


Mild prolonged chronic hyponatremia is independently associated with hip fracture risk in the elderly population, although the absolute risk is low. However, proof that correcting hyponatremia will result in a reduction of hip fractures is lacking.


bone; falls; hip fracture; hyponatremia; osteoporosis

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