Mild Hyponatremia Is Not Associated With Degradation of Trabecular Bone Microarchitecture Despite Bone Mass Loss

Hyponatremia is associated with increased risk of osteoporosis and fractures. The impact of hyponatremia on noninvasive indices of bone quality, however, is unknown.

To evaluate whether trabecular bone microarchitecture, assessed noninvasively by trabecular bone score (TBS), is altered in patients with hyponatremia.

We conducted a cross-sectional analysis of the population-based 2005-2008 cycles of the National Health and Nutrition Examination Survey, in which TBS measurement was performed. The main outcome measures were TBS values and bone mineral density (BMD) T-scores at the lumbar spine, total hip and femoral neck.

A total of 4204 subjects aged 50 years or older were included (4041 normonatremic, 163 hyponatremic-90.8% with mild hyponatremia). Univariate analyses did not show any difference in TBS between patients with and without hyponatremia (1.308 ± 0.145 vs 1.311 ± 0.141, P = .806). Hyponatremic subjects had lower BMD T-score at total hip (-0.70 ± 1.46 vs -0.13 ± 1.32, P < .001) and femoral neck (-1.11 ± 1.26 vs -0.72 ± 1.14, P = .004), while no difference was observed at lumbar spine (-0.27 ± 1.63 vs -0.31 ± 1.51, P = .772). After adjustment for relevant confounders, hyponatremia was confirmed as an independent predictor of lower BMD T-score at the total hip (β = -0.20, 95% confidence interval [CI]: [-0.39, -0.02], P = .029), while the significance was lost at the femoral neck (P = .308). Again, no association between hyponatremia and lumbar spine BMD (P = .236) or TBS (P = .346) was observed.

Hyponatremia, at least in mild forms, is not associated with a degradation of trabecular microarchitecture, assessed noninvasively by TBS. An independent association between hyponatremia and loss of bone mass is confirmed, particularly at the total hip.