Somatostatin Impairs Sleep in Elderly Human Subjects

With increasing age, sleep becomes more shallow and fragmented and sleep-associated growth hormone (GH) release declines. GH secretion is regulated physiologically by opposite actions of GH-releasing hormone (GHRH) and somatostatin (SRIF). The administration of GHRH promotes sleep in both young and elderly controls, whereas SRIF does not induce sleep-EEG changes in young subjects. Because the influence of peripheral SRIF administration on sleep EEG in the elderly is unknown, we administered 50 μg SRIF-14 every hour between 2200 and 0100 hours to controls with an age range from 60 to 73 years (mean ± SD 67.4 ± 5.1 years). After SRIF administration, total sleep time and rapid eye movement (REM) sleep decreased significantly, and more time was spent awake in the first sleep cycle, suggesting that SRIF induces sleep deterioration in the elderly. The peptide may become more effective on sleep EEG in older than in younger subjects, because of the decline of GHRH–GH axis activity, which may contribute to sleep disturbances in aging. The increased efficacy of SRIF in the elderly also may be explained by enhanced leakage of the blood-brain barrier.