Heart Rate Variability-An Index of the Efficacy of Complementary Therapies in Irritable Bowel Syndrome: A Systematic Review

Abstract

Irritable bowel syndrome (IBS), as a functional and psychosomatic disease, reduces the quality of life and increases the risk of developing mental disorders. Deregulation of the autonomic nervous system (ANS) is one of the main causes of the disease. The objective of the present study was to identify the studies in which measurements of heart rate variability (HRV) were performed before and after therapeutic intervention, and to evaluate the effectiveness of IBS therapy in terms of a reduction of IBS symptoms and changes in autonomic tone. A systematic review of the literature was carried out in accordance with PRISMA standards. Six databases were searched for articles published before 2022: PubMed^®, MEDLINE^®, EBSCO, Cochrane, Scopus, and Web of Science. Inclusion criteria were experimental design, diagnosis of IBS (medical and/or diagnosis in accordance with the Rome Criteria), non-pharmacological intervention, and HRV measurement before and after the intervention. The quality of the studies was assessed by JBI Critical appraisal. In total, 455 studies were identified, of which, sixwere included in the review. Expected changes in HRV (increase in parasympathetic activity) were observed in four of the six studies (interventions studied: ear acupressure, transcutaneous auricular vagusnerve stimulation, cognitive behavioral therapy with relaxation elements, yoga). In the same studies, therapeutic interventions significantly reduced the symptoms of IBS. The present review indicated that interventions under investigation improve the efficiency of the ANS and reduce the symptoms of IBS. It is advisable to include HRV measurements as a measure of the effectiveness of interventions in IBS therapy, and to assess autonomic changes as a moderator of the effectiveness of IBS therapy.

Keywords: complementary therapies; heart rate variability; irritable bowel syndrome; mind-body therapies.

Figure 1

Schema the relationship between disturbed autonomic balance and IBS symptoms. Note: Permanent stress and negative emotions inhibit the vagus nerve function, which manifests itself in hypoactivity of the PNS. Under the stress, the homeostasis of the intestinal epithelium is disturbed, and the microbiota composition is modified, e.g., reduction of fecal microbial diversity, which may lead to dysbiosis. Impaired secretory and barrier functions of the intestinal mucosa are characterized by increased intestinal permeability and secretion, which contribute to the development of intestinal inflammation and disturbances in intestinal motility. Inflammation causes pain, problems with defecation (diarrhea/constipation), and the visceral hypersensitivity increases. These symptoms affect neurophysiological changes (including lowering the pain threshold) and mental changes (increased anxiety, depression) in the brain, which secondarily generates stress and reduces the anti-inflammatory efficiency of the vagus nerve. This simplified elaboration is based on Bonaz et al., 2018 [11] and Drossman, 2016 [1].

Figure 2

Flow diagram for systematic review.