Circadian rhythms of adenosine deaminase activity in human erythrocytes: a transverse study on young, elderly and senile demented subjects.

Adenosine deaminase activity (ADA) was determined around the clock in human plasma from different groups of subjects: presumably clinically healthy women in Minneapolis, USA; healthy medical students, healthy elderly men and women, and mentally ill patients in Paris, France. In addition to analyses of variance, circadian characteristics were estimated individually and summarized by population-mean cosinor for each group. Technical and sampling considerations are documented: the individualized assessment of a circadian rhythm in adenosine deaminase is feasible in 8 out of 11 series from clinically healthy women covering 24h at 20-min intervals. A circadian population rhythm could be determined for the elderly men and women (p less than 0.05) and tentatively (p = 0.053) for the senile demented patients. A difference in circadian group rhythm characteristics found between the healthy elderly subjects and patients with senile dementia deserves further exploration.