Is asymptomatic hyponatremia really asymptomatic?

Consequences of hyponatremia are generally mild and remain unnoticed by both physician and patient. When water restriction, usually prescribed to avoid water intoxication, fails to normalize serum sodium values, clinicians will tolerate mild stable hyponatremia (especially when serum sodium is >125 mEq/L [1 mEq/L = 1 mmol/L]). In a recent study, we observed that mild chronic hyponatremia contributes to an increased rate of falls, probably due to impairment of attention, posture, and gait mechanisms. Eight attention tests were used to assess 16 patients with asymptomatic hyponatremia (mean serum sodium, 128 +/- 3 mEq/L) due to syndrome of inappropriate antidiuretic hormone secretion. On attention tests for visual and auditory stimuli, there was an increase in mean response latency of 58 msec (P