39. Vagus nerve activity, a good night’s sleep, and recovery from acute infection

Abstract

Under normal circumstances, “falling asleep” is preceded by changes in autonomic signaling, notably increased parasympathetic (vagal) activity and reduction of sympathetic drive with a concomitant reduction in heart rate (HR) and increase in HR variability (HRV). In a series of studies we examined a role for nocturnal cardiac vagal activity in the experience of restorative sleep, and in mediating recovery from acute infection. HR was continuously monitored (via ECG) on two occasions in healthy students; in patients with CFS and matched healthy controls; and in an initial sample of patients with acute infective illness. Questionnaires assessed demographic information, physical and psychological state, and sleep quality. Vagal activity was inferred from HRV parameters; actimetry served to monitor sleep. The inflammatory marker, C-reactive protein, was quantified by ELISA in participants with acute infection. Repeated recordings of nocturnal HRV in healthy individuals showed a high level of reproducibility and were strongly linked to sleep quality. Compared to matched healthy participants, nocturnal HRV was significantly lower in patients with CFS and proved to be the best predictor of key sleep outcome variables. In patients with acute infections increased HRV was significantly associated with lower levels of C-reactive protein and shorter illness duration. This research confirmed that nocturnal vagal activation facilitates the recuperative effects of sleep and suggests a possible role for vagal activity in recovery from acute infection.