Autonomic functioning in irritable bowel syndrome measured by heart rate variability: a meta-analysis.

OBJECTIVE

To analyze autonomic functioning which presented as the high frequency (HF) component of heart rate variability, a measurement of vagal tone, and the ratio of low frequency (LF) to HF (LF : HF), an indicator of sympathovagal balance in irritable bowel syndrome (IBS) patients.

METHODS

We identified relevant studies by performing a literature search of MEDLINE, EMBASE and the ISI Web of Knowledge to 31 March 2013. Pooled effect sizes with 95% confidence interval (CI) were calculated using a random effects model. Between-study heterogeneity was assessed using the Q test and I(2) statistic.

RESULTS

In all, 11 articles including 392 IBS patients and 263 controls met the inclusion criteria of the analysis. IBS patients had lower HF band power (Hedges's g = -0.38, 95% CI -0.68 to -0.09) than the controls (I(2)  = 63.6%, P = 0.003). Moreover, IBS patients showed a higher LF : HF (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 for the IBS patients and controls. Additionally, constipation-predominant IBS (IBS-C) patients had decreased HF band power, whereas no significant difference was found in LF : HF.

CONCLUSIONS

Impaired parasympathetic functioning and abnormal sympathovagal balance may be involved in the pathogenesis of IBS. Vagal dysfunction is more obvious in the IBS-C subgroup.