Sleep-related autonomic disturbances in symptom subgroups of women with irritable bowel syndrome.

The objective was to investigate whether predominant symptom patterns in women with irritable bowel syndrome (IBS) affect autonomic activity during sleep. Seventy-five women with IBS underwent a polysomnographic sleep study. Twenty-two of the IBS patients were diarrhea-predominant (IBS-D), 33 were constipation-predominant (IBS-C), and 20 patients had alternating symptoms (IBS-A). Autonomic activity was measured by heart rate variability. The IBS-D group had significant vagal withdrawal compared to the IBS-A group during REM and non-REM sleep (P < 0.05). The IBS-D symptom subgroup had significantly (P < 0.05) greater sympathetic dominance during non-REM than IBS-A patients. Lower abdominal pain correlated with sympathetic dominance during sleep in the IBS-D group (r=0.54, P < 0.01). The IBS-D patients were physiologically distinct with regard to autonomic functioning during sleep compared to the alternating patients, but not the constipated patients. Sleep appears to unmask differences in autonomic activity that may distinguish IBS patients.