Abstract:

BACKGROUND: Mild hyponatremia (serum sodium 130-135 mEq/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.
METHODS: We enrolled 75 participants with mild hyponatremia and 2907 with normonatremia (serum sodium, 136-145 mEq/L) aged ≥70 years 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.
RESULTS: One-way analysis of covariance showed that elderly participants with mild hyponatremia had lower SMI (7.1 ± 0.2, 7.2 ± 0.2 kg/m2, p = 0.04), weaker GS (19.1 ± 1.9 vs 21.4 ± 1.8 kg, p = 0.01), slower WS (0.9 ± 0.1 vs 1.1 ± 0.1 m/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.

日本語要旨:

もの忘れ外来受診者において、軽度低ナトリウム血症と筋量、身体機能、認知機能との関連を調査した。軽度低ナトリウム血症は、筋量とは関連を認めなかったが、歩行速度、片脚立位時間などの身体機能や、抑うつと関連することを示した。