Impairment of Neurocognitive Functioning, Motor Performance, and Mood Stability in Hospitalized Patients With Euvolemic Moderate and Profound Hyponatremia

BACKGROUND:The impact of chronic moderate and profound hyponatremia on neurocognitive perfor-mance, motor skills, and mood stability has not been investigated systematically so far, and results regard-ing mild to moderate hyponatremia are inconsistent. Furthermore, it is not known whether treatment hasan effect on outcome in these patients.METHODS:A total of 130 hospitalized patients with confirmed euvolemic hyponatremia (<130 mEq/L)were subjected to a test battery (Mini-Mental State Examination, DemTect, Trail-Making Tests A and B,Beck Depression Inventory, Timed-up-and-go Test) before and after treatment; additionally, 50 normona-tremic group-matched patients served as reference group.RESULTS:The scores of all tested domains were significantly worse in the hyponatremia group (medianserum sodium [Na+] 122 (119-126) mEq/L) as compared to the reference group (P<0.001), and the oddsof obtaining a pathological test result increased markedly with more profound hyponatremic states (oddsratios between 5.0 and 21.8 in the group with Na+<120 mEq/L compared to reference group). Inversely,treatment led to a significant amelioration of all test results with medium to large effect sizes. Linearregression models revealed the increment of Na+as an important predictor of test outcome.CONCLUSION:We demonstrate a clear association between lower levels of Na+beyond mild hyponatremiaand impairment of neurocognitive and motor performance as well as mood disorders. Our analysis furthersuggests a causal role of hyponatremia in this context. However, there are apparent differences betweenthe distinct tested domains warranting further investigations.