Autonomic Dysregulation During REM Sleep

There has long been a recognized link between sleep and the autonomic nervous system in both health and disease. This relationship is by far best described in the context of cardiovascular mechanisms, where the autonomic nervous system exerts exquisite control with continuous and rapid adjustments of heart rate (HR), cardiac contractility, vasomotor tone, and vascular capacitance to maintain blood pressure and flow to vital organs. Vasoconstriction in response to sympathetic nervous stimulation modulates distribution of blood flow, particularly in cutaneous, splanchnic, renal, and skeletal muscle vasculature, although less so in cerebral vessels. HR and contractility are influenced by both vagal and sympathetic neural output. Autonomic impulses to the vasculature and heart originate from the vasomotor center in the brain stem, which in turn is modulated by higher nervous regions in the mesencephalon, diencephalon, and portions of the cerebral cortex. Thus, global and regional changes in brain activity have powerful effects on autonomic output, such as during the state change from wakefulness to sleep or, in contrast, those accompanying the increased brain activity characteristic of rapid eye movement (REM) sleep. Although dreaming is thought to occur primarily during REM sleep, the exact function of this sleep stage remains a mystery, but it is clear that physiologic processes that occur during REM sleep have a potentially major impact on cardiopulmonary homeostasis.