Daily rhythm of serum melatonin in patients with dementia of the degenerate type

The daily rhythm in serum melatonin levels was measured in patients with dementia of the degenerate type (Alzheimer's disease, Pick's disease and senile dementia of the Alzheimer type) by radioimmunoassay. Thirteen patients (age: 69.0 +/- 8.0 years, mean +/- S.D.) were studied. All patients were hospitalized at the time of the study and had a history of sleep-wake disturbances, nocturnal wandering and/or delirium. We also studied 13 age-matched healthy control subjects (control group 1), ten young adults (control group 2), and nine hospitalized patients without dementia (control group 3). Two subjects in the control groups showed no measurable changes in melatonin level throughout the day, while the other 30 control subjects exhibited a clear daily rhythm with the peak concentration occurring during the night. On the other hand, four out of the 13 patients with dementia did not show any melatonin rhythm. Two of the demented patients who did not exhibit melatonin rhythm displayed clinical symptoms of rhythm disorders. One out of the nine patients with melatonin rhythm presented with clinical symptoms, such as delirium and sleep-wake disturbance. Our results suggest that the probability of absent melatonin rhythm is higher in demented patients compared with subjects without dementia. However, a lack of melatonin rhythm is not always associated with symptomatic rhythm disorders. Since the melatonin rhythm reflects that of the suprachiasmatic nucleus, it follows that the SCN function of the patients having a history of rhythm disorders was not always severely damaged.