Serum melatonin rhythm in demented patients

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The daily rhythm of serum melatonin levels in patients with Alzheimer's disease was measured, in order to see whether patients with a history of the daily rhythm disorders show a pattern of melatonin rhythm different from that of normal subjects.Sixteen hospitalized patients with Alzheimer's disease were studied. The degrees of abnormality were moderate or severe. The mean age of these patients was 69 years. As control groups, 13 age-matched healthy people and 10 healthy young adults were measured. Blood samples were collected every 3h over a period of 24h. Serum melatonin was measured by radioimmunoassay procedure.Demented patients are inclined to suffer rhythm disorders. However, nearly 63% of the Alzheimer patients showed melatonin rhythm. The data suggest that the oscillators of these patients are functioning. Although the precise mechanism and pathogeneses of Alzheimer's disease are not identified at present, the rhythm disorder appears more often in the advanced stage of dementia. The sensitivity of the clock to the Zeitgebers decreases with aging. So, the sensitivity to the Zeitgebers, not only the disorder of the SCN and the related nervous pathways, must have an important role for the occurrence of the rhythm disorder in demented patients. Improving the Zeitgebers for the less-sensitive biological clock system may help to recover from the rhythm disorders.