Twenty-four-hour beta-endorphin secretory pattern in Alzheimer's disease

A chronobiological study was carried out in 6 male patients (67-71 years), suffering from Alzheimer-type dementia (ATD) and 6 male patients (52-74 years) suffering from multi-infarct dementia (MID), to evaluate their 24-hour beta-endorphin and cortisol secretory patterns. Six healthy male adults (28-37 years) and 6 healthy elderly male subjects (78-84 years) constituted the control groups. Blood samples were drawn every 4 h from 8.00 to 20.00 h and every 2 h from 24.00 to 6.00 h. Mean 24-hour beta-endorphin levels were significantly (p < 0.05) higher in the ATD patients (39.2 +/- 1.5 ng/l) than in the other groups (33.8 +/- 1.1, 30.1 +/- 1.6 and 33.2 +/- 1.1 ng/l in the elderly subjects, the adults and the MID patients, respectively). The circadian rhythm was absent in the ATP patients, in the elderly subjects and the MID patients. No differences in plasma cortisol circadian rhythm were observed among the four groups. Our data indicate that changes in circulating beta-endorphin concentrations and circadian pattern may be due to the aging process.