Interpreting Heart Rate Variability in Sleep: Why, When, and How?

Sleep and the autonomic nervous system (ANS) are biologically and clinically associated. Neuronal pathways located in the brain stem and basal forebrain responsible for the wake–sleep transition are connected with areas of the central nervous system regulating ANS activity. Indeed, at the forebrain diencephalic level, sleep itself may be considered to be one of the most highly integrated autonomic functions in which behavioral and homeostatic integration occurs. In turn, this integration is bidirectionally interconnected with the other hierarchical levels.