Is asymptomatic hyponatremia really asymptomatic?

Area of Science:

• Nephrology
• Geriatrics
• Neurology

Background:

• Mild hyponatremia is often overlooked and considered asymptomatic.
• Clinicians may tolerate stable mild hyponatremia, especially serum sodium >125 mEq/L.
• The potential consequences of mild chronic hyponatremia on neurological function are not well understood.

Purpose of the Study:

• To investigate the impact of mild chronic hyponatremia on attention, posture, and gait.
• To determine the association between mild hyponatremia and the risk of falls.
• To challenge the concept of asymptomatic hyponatremia.

Main Methods:

• Assessed 16 patients with asymptomatic hyponatremia using eight attention tests and gait analysis (tandem walk).
• Compared performance on attention and gait tests with normonatremic controls and age-matched volunteers with alcohol intake.
• Analyzed hospital admission data for 122 patients with mild hyponatremia, focusing on fall-related admissions.

Main Results:

• Patients with hyponatremia showed increased response latency (58 msec) and errors (20%) on attention tests (P <0.001).
• Gait stability was impaired in hyponatremic patients, with greater center of pressure travel (1.3 vs 1 m, P <0.003).
• In a cohort of 122 patients, 21% were admitted for falls; adjusted odds ratio for falls in hyponatremia was 67.

Conclusions:

• Mild chronic hyponatremia significantly impairs attention, posture, and gait mechanisms.
• The concept of asymptomatic hyponatremia is not supported by detailed analysis of falls or sensitive neurological tests.
• Hyponatremia is a significant, independent risk factor for falls, even at mild serum sodium levels.