Objectives: The vagus nerve influences the modulation of pain. Chronic pain is associated with disturbance of the descendent inhibitory pathway (DIP). Heart rate variability (HRV) is a proxy measure for vagal activity and may reflect dysfunction of the DIP. We aimed to investigate the association of HRV and pain in individuals with and without chronic pain.
Materials and methods: Drawing on cross-sectional data from 647 individuals, the present study explores the association of HRV and pain. The root mean square of successive differences (RMSSD), corresponding to parasympathetic regulation of the heart, was derived from 24-hour electrocardiogram recordings. Pain, demographic data, and health behaviors were assessed by self-administered questionnaires. Blood pressure was measured and inflammatory markers (white blood cell count, C-reactive protein, and fibrinogen) were analyzed from fasting blood samples.
Results: Those with chronic pain reported lower RMSSD. Results revealed a negative correlation of HRV and pain in multivariate-adjusted analysis only in respondents without chronic pain.
Discussion: Our results suggest that the DIP indexed by vagal activity operationalized as RMSSD is disturbed in persons with chronic pain. Furthermore, the correlations between RMSSD and pain are different between those without and those with chronic pain. The findings are discussed, emphasizing changes in brain activity and the comorbid dysregulation of emotion in patients with chronic pain, to provide implications for the treatment of chronic pain.