Mild hyponatremia is associated with low skeletal muscle mass, physical function impairment, and depressive mood in the elderly

BackgroundMild hyponatremia (serum sodium 130-135mEq/L) is a common electrolyte disorder in the elderly. However, its association with both sarcopenia and cognitive function remains to be clarified. Therefore, here we investigated the association of mild hyponatremia with skeletal muscle mass, physical function, and cognitive function in the elderly.MethodsWe enrolled 75 participants with mild hyponatremia and 2907 with normonatremia (serum sodium, 136-145mEq/L) aged >= 70years who visited the Memory Disorder Outpatient Center of Japan's National Center for Geriatrics and Gerontology. Skeletal muscle mass index (SMI), grip strength (GS), walking speed (WS), one-leg standing (OLS) test times, and neuropsychological test scores were determined.ResultsOne-way analysis of covariance showed that elderly participants with mild hyponatremia had lower SMI (7.10.2, 7.2 +/- 0.2kg/m(2), p=0.04), weaker GS (19.1 +/- 1.9 vs 21.4 +/- 1.8kg, p=0.01), slower WS (0.9 +/- 0.1 vs 1.1 +/- 0.1m/s, p=0.001), and higher GDS- 15 score (6.4 +/- 0.9 vs 5.2 +/- 0.9, p=0.002) than those with normonatremia. Multiple logistic regression analysis indicated that mild hyponatremia was independently associated with sarcopenia (odds ratio [OR]: 2.2, p=0.02), slower WS (OR: 5.3, p=0.04) and shorter OLS time (OR: 2.5, p=0.02) as well as with severe depressive mood (OR: 2.6 p=0.006) but not with SMI (OR: 1.6, p=0.2) or GS (OR: 1.9, p=0.09).Conclusions Our results suggest that elderly people with even mild hyponatremia had physical function impairment and depressive mood.

Automated summary

The study found that mild hyponatremia is associated with reduced skeletal muscle mass, impaired physical function, and depressive mood in the elderly.