Hyponatremia, a risk factor for osteoporosis and fractures in women

Hyponatremia has been linked to an increased risk of osteoporosis and fractures. We found an increased hazard ratio of major osteoporotic fractures adjusted for potential confounders, including osteoporosis and medication. A reduced BMD was not sufficiently explaining the association. Our data indicate that hyponatremia should be considered a risk factor for osteoporosis and fractures.

INTRODUCTION: Hyponatremia is the most common electrolyte disorder in clinical practice and could be a risk factor for both osteoporosis and fractures. Mild hyponatremia has traditionally been regarded as a benign and asymptomatic condition; however, data from large population and animal studies have led to a reappraisal of this view. The purpose of this study was to evaluate the association of hyponatremia with osteoporosis and major osteoporotic fractures (MOF) in women.

METHODS: This is a historical cohort study with fracture follow-up. The study consisted of 5610 patients with available serum sodium and a bone density measurement. Information on potential risk factor was obtained through a questionnaire. Additional information on medication, comorbidities, and fractures was obtained through national registries.

RESULTS: Hyponatremia was associated with significant lower T-scores at total hip and a borderline significant lower T-score at femoral neck in the multivariate analysis. No association was found between hyponatremia and the lumbar spine T-score. Hyponatremia was associated with an increased hazard ratio of sustaining a MOF in the period from 6 months prior to 12 months after serum sodium measurement. Finally, data showed a relationship with increasing serum sodium and an increasing T-score estimate and a decreasing hazard ratio of MOF.

CONCLUSIONS: Our data suggest that hyponatremia in women increases the risk of osteoporosis and MOF. The increased risk of MOF was independent of osteoporosis.