Electrolytes and cognitive function in the elderly: relationship between serum sodium and chloride concentrations and psychometric test scores.

BACKGROUND It is well known that nutritional status and CNS functions are closely related. Malnutrition leads to an impaired cognitive performance, and mental disturbances may be responsible for alterations in eating behaviour. The correlation between nutritional and cognitive status seems to be even closer in the elderly because of the higher incidence of neuropsychic syndromes and malnutrition. METHODS Given this background, we set up this study in order to correlate cognitive status (investigated using the Mini-Mental State Examination--MMSE--and the Geriatric Depression Scale--GDS) and various biochemical nutritional indicators (serum electrolytes, albumin, transferrin, erythrocytes, lymphocyte count, hematocrit, hemoglobin, total cholesterol, HDL cholesterol, triglycerides and total proteins) in 82 apparently healthy elderly people (mean age +/- SD 87 +/- 6). RESULTS Our data demonstrated a correlation between the MMSE score (26 +/- 2) and Na (138.1 +/- 3.0 mmol/L, r = -0.66, p < 0.001) and Cl (102.4 +/- 4.5 mmol/L, r = -0.62, p < 0.001) serum electrolytes, but no correlation with the other nutritional data. The demonstrated relationship does not appear to be causal because Na and Cl are chemically and physiologically linked. CONCLUSIONS These correlations underline the relevance of the correct intake and metabolism of electrolytes for functional CNS activity in the elderly.