Pathophysiology underlying irritable bowel syndrome--from the viewpoint of dysfunction of autonomic nervous system activity.
ABSTRACT Although irritable bowel syndrome (IBS) is the most common gastrointestinal disease and is found in up to 50% of patients referred to gastroenterologists, its pathogenesis remains unexplained. Lately most attention has been focused on visceral hypersensitivity related to dysfunction of the autonomic nervous system. Although there have been many reports regarding the autonomic nervous system in IBS patients, the results have not always been consistent. In many studies, increased sympathetic nervous system activity and decreased parasympathetic nervous system activity have been the most frequently noted differences when IBS patients are compared with healthy controls. There are also some differences among IBS symptom subgroups and some differences between men and women. Data from previous studies have been inconsistent, with complicating factors resulting in difficulties in classification and the possibility of multiple physiological pathways for a similar symptom picture. Further studies based on the Rome III criteria are required to evaluate whether or not autonomic functions significantly differ from each other. However, although there are many methods of measurement for evaluation of the autonomic nervous system, there are few of these methods that are not only accurate but also cost-effective, non-invasive, and easy to perform. Recently, we developed a new method with the abovementioned advantages for measuring fingertip blood flow in evaluating the autonomic nervous system by continuous-wave Doppler sonography. Using this method, we found that abnormal fingertip blood flow responses suggested the presence of excess sympathetic activity.
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ABSTRACT: To analyze automatic functioning which presented as the high frequency (HF) component of heart rate variability (HRV), a measurement of vagal tone, and the low frequency (LF)/HF ratio, an indicator of sympathovagal balance, in IBS patients. We identified relevant studies by performing a literature search of MEDLINE, EMBASE, and the ISI Web of Knowledge until March 31, 2013. Pooled effect sizes with 95% confidence interval (CI) were calculated using a random-effects model. Between-study heterogeneity was assessed using Q test and I(2) statistic. Eleven articles including 392 IBS patients and 263 healthy controls were included in the analysis. The IBS patients had lower HF band power (Hedges's g = -0.38; 95% CI -0.68 to -0.09) than the healthy controls (I(2) = 63.6%, P = 0.003). Moreover, IBS patients showed a higher LF/HF ratio (Hedges's g = 0.43, 95% CI 0.13-0.74), with no significant heterogeneity. A subgroup analysis of the HF index according to the recording time yielded different results between the IBS patients and healthy controls. Additionally, constipation-predominant IBS (IBS-C) patients had decreased HF band power, whereas no significant difference was found for the LF/HF ratio. Impaired parasympathetic functioning and abnormal sympathovagal balance may be involved in the pathogenesis of IBS. Vagal dysfunction was more obvious in the IBS-C subgroup.Journal of Digestive Diseases 08/2013; DOI:10.1111/1751-2980.12092 · 1.92 Impact Factor
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ABSTRACT: Objective : To determine if cognitive processing, and subjective and physiological responses to stress and relaxation differed between an irritable bowel syndrome (IBS) group and control group. How these variables relate to the severity of IBS symptoms was also determined. Methods : Twenty-one IBS participants and 20 controls provided cognitive (attention and processing), subjective (perceived stress and vigour), and physiological (heart rate, blood pressure, and skin conductance) data during a relaxation and stress phase. Logistic regression analyses determined which variables related to the IBS group and hierarchical linear regression assessed how the variables related to the severity of IBS symptoms. Results : Subjective and cognitive factors (drowsiness at baseline, total vigour, and reduced Stroop colour-naming accuracy for negative words) significantly related to IBS, χ2 (3, N = 41) = 23.67, p < .001, accurately categorising 85% of participants. IBS symptom severity was associated with both subjective (drowsiness at baseline and a smaller reduction in tiredness from relaxation to stress) and physiological (smaller increase in systolic blood pressure from baseline to stress phase and lower skin conductance at baseline) variables. This model predicted IBS severity, F (4, 16) = 11.20, p < .001, and accounted for 74% of the variability in scores. Conclusions : A negative attention bias, which may be related to a negative self-schema, as well as perceived low vigour were important in categorising IBS. Low subjective vigour and reduced physiological reactivity to both relaxation and stress conditions was associated with IBS severity, suggestive of illness-related allostatic load.Journal of Psychosomatic Research 07/2014; DOI:10.1016/j.jpsychores.2014.04.009 · 2.84 Impact Factor
The American Journal of Gastroenterology 01/2015; 110(1):18-44. DOI:10.1038/ajg.2014.395 · 9.21 Impact Factor