PHYSIOLOGY OF SLEEP (REVIEW)–Interactions between stress and sleep: from basic research to clinical situations

Acute stress is a fundamental adaptive response which enables an organism to cope with daily threatening environmental stimuli. If prolonged and uncontrollable, the stress response may become inadequate and ultimately result in health damage. Animal models of stress in rodents indicate that both acute and chronic stressors have pronounced effects on sleep architecture and circadian rhythms. One major physiological response elicited by stress is activation of the hypothalamo-pituitary-adrenal axis. In both animals and humans, the hypothalamo-pituitary-adrenal axis plays an important role in sleep–wake regulation and in alterations of the sleep–wake cycle secondary to exposure to acute or chronic stressors. In humans, dysfunction of the neuroendocrine regulation of sleep can lead to severe sleep disturbances. The progressive decay of the hypothalamo-pituitary-adrenal axis in elderly people, which mimics chronic exposure to stress, may contribute to fragmented and unstable sleep in ageing. Shift workers, chronic insomniacs or patients suffering from mental disorders show abnormal hypothalamo-pituitary-adrenal secretory activity and concomitant sleep disturbances. Those sleep disorders and possible underlying mechanisms are briefly reviewed.