Low vagal tone is associated with impaired post stress recovery of cardiovascular, endocrine, and immune markers.

Reduced heart rate variability (HRV) and delayed blood pressure recovery are associated with increased cardiovascular risk. Besides this evident link, the vagus is thought to play an inhibitory role in the regulation of other allostatic systems, including inflammation and the hypothalamic-pituitary-adrenal (HPA) axis. However, human evidence is scarce. To further explore these associations and with special regard to the postulated mediating role of the vagus, we hypothesised that subjects with low vagal tone as indexed by reduced resting HRV would show impaired post-stress recovery of cardiovascular, endocrine and immune system markers involved in cardiovascular pathology. 44 healthy men underwent a standardised mental stress test. Besides continuous measurement of systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), and HRV serum cortisol, tumour necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were measured before, after, 20, and 60 min after stress. Low versus high HRV groups was defined by median split on resting HRV (RMSSD). The task elicited significant time effects for SBP, DBP, HR, HRV, cortisol, and TNF-alpha. Subjects with low baseline HRV showed almost no modulation of HRV coupled with overall reduced HRV levels, and impaired recovery of DBP, cortisol, and TNF-alpha. Confirming our hypothesis, low vagal tone was associated with impaired recovery of cardiovascular, endocrine, and immune markers in healthy males. The data support an inhibitory role of the vagus in the regulation of allostatic systems as described in the neurovisceral integration model. We posit reduced resting HRV as a risk marker for future cardiovascular and other stress-related disease.