Is autonomic function associated with (central) pain processing in individuals with chronic pain? A systematic review

Abstract

Background and aims: Dysfunctions of the autonomic ner­ vous system (ANS) are hypothesized to be associated with al­ tered central pain processing (CPP). Altered CPP characterizes nociplastic pain, which is common in non-specific chronic pain conditions. However, the exact interaction between ANS func­ tion and chronic pain remains unclear. Methods: PubMed, SCOPUS, and Web of Science were searched, followed by a two-phased screening by two indepen­ dent researchers (IM & CQ). Risk of bias (Newcastle-Ottawa Scale), level of evidence and data collection were performed double-blind. Results: Two cohort studies, 10 cross-sectional studies, and one case-control study were included. ANS function was measured by cardiovascular measurements (blood pressure, heart rate, and heart rate variability), sympathetic skin response, plasma catecholamines, and skin temperature. All studies used ques­ tionnaires to assess pain, nine used additional quantitative sensory testing. Significant associations between autonomic function (heart rate and blood pressure) and pain intensity (VAS) were found in patients with Irritable Bowel Syndrome (p < 0.05). Patients with chronic musculoskeletal pain showed significant associations between conditioned pain modulation