Evidence for Autonomic Nervous System Imbalance in Women with Irritable Bowel Syndrome

Autonomic nervous system function was assessedin women with and without irritable bowel syndrome usingfrequency domain measures of heart rate variability.Women were interviewed and placed into the irritable bowel syndrome (N = 25) group based on historyof diagnosis and self-report of current gastrointestinalsymptoms. Women in the control group denied a history ofchronic gastrointestinal symptoms (N = 15). Women werefollowed for one menstrual cycle with a symptom diary,and during mid-luteal phase they wore a Holter 24-hrelectrocardiograph monitor. Women with irritable bowelsyndrome demonstrated significantly lower vagal tone as measured by the highfrequency spectrum relative to control women. Inaddition, women with irritable bowel syndrome had aflattened 24-hr pattern of heart rate variability, withsignificantly lower levels of vagal tone during sleep. Theseresults suggest that systemic sympathovagal balance maybe shifted in a subset of women with irritable bowelsyndrome.