Circadian organization of serum electrolytes in physiological aging.

Age-related structural and neurochemical changes occurring in the central nervous system have been related to changes in some rhythmometric parameters. In spite of their clinical importance, only a few studies have investigated the modifications over time of serum electrolytes in senescence. The aim of our study was to evaluate the circadian pattern of serum potassium, chloride, sodium, calcium and phosphorus in 30 clinically healthy elderly subjects, with no cognitive impairment, and to compare the findings with those given by 24 healthy young controls. The subjects were synchronized as regards their daily activities, sleeping/waking habits, time/quality of meals and dietary electrolyte intake. After an overnight fast, samples were taken beginning at 08.00 and every 4 h thereafter until 20.00, and every 2 h from 20.00 to 04.00. Both the young and the elderly subjects exhibited statistically significant circadian rhythms for all serum electrolytes considered. Our findings suggest that circadian organization of serum electrolytes is maintained in physiological aging, even though it should be noted that sodium and phosphorus acrophases differed significantly in the two experimental groups.