Autonomic regulation of cardiac function during sleep in patients with irritable bowel syndrome

Several studies have provided evidence of abnormal autonomic activity in irritable bowel syndrome (IBS), suggesting that abnormal central nervous system-autonomic nervous system arousal mechanisms may be part of its pathophysiology. The goal was to investigate cardiac sympatho-vagal balance during waking and the different stages of sleep using heart rate variability analysis in IBS patients compared to healthy controls.

A total of 15 IBS patients (13 female, two male, mean age 34.9 +/- 2.1 yr) and 15 controls (13 female, two male, mean age 36.2 +/- 2.3 yr) were studied during 1 h of pre-sleep quiet waking and during seven-hours of sleep. Polysomnography was used for the determination of state of consciousness. Electrocardiography provided the beat-to-beat intervals, which were then subjected to spectral analysis for determination of the percentage of energy in the low and high frequency bands, respectively. The low frequency/high frequency band ratio was also calculated. For each subject, heart rate variability analysis was performed using 15-min segments of waking, non-rapid eye movement sleep, and rapid eye movement sleep.

The low frequency band power was significantly greater in IBS patients during waking. No group differences were found in high frequency band power during any state. The low frequency to high frequency band ratio was significantly greater in IBS patients during rapid eye movement sleep.

IBS patients have greater sympathetic activity during waking and greater overall sympathetic dominance during rapid eye movement sleep. These results support the presence of autonomic abnormalities in patients with IBS. The possibility is discussed that sympathetic dominance during rapid eye movement sleep may play a role in sensitizing the gut to waking stimulation.