Relationships of abdominal pain, reports to visceral and temperature pain sensitivity, conditioned pain modulation, and heart rate variability in irritable bowel syndrome.

Background Irritable bowel syndrome ( IBS) is a heterogeneous condition with a number of pathophysiological mechanisms that appear to contribute to symptom chronicity. One of these is altered pain sensitivity. Methods Women between ages 18-45 were recruited the community. Of those enrolled, 56 had IBS and 36 were healthy control ( HC) women. Participants completed questionnaires, kept a 4-week symptom diary and had a 12-h Holter placed to assess nighttime heart rate variability including high frequency power ( HF), low frequency power ( LF), and total power ( TP). At mid-follicular phase approximately 80% of women completed a thermal pain sensitivity test with conditioned pain modulation and visceral pain sensitivity using a water load symptom provocation ( WLSP) test. Key Results As expected, daily abdominal pain was significantly higher in the IBS compared to HC group. There were no differences between the bowel pattern subgroups ( IBS-diarrhea [ IBS-D], IBS-constipation plus mixed [ IBS- CM]). Thermal pain sensitivity did not differ between the IBS and the HC groups, but was significantly higher in the IBS- CM group than the IBS-D group. In the WLSP test, the IBS group experienced significantly more symptom distress than HCs and the IBS- CM group was higher than the IBS-D group. Heart rate variability indicators did not differ between the groups or IBS subgroups. Daily abdominal pain was positively correlated with LF and TP in the IBS group. Conclusions & Inferences Despite similar levels of abdominal pain in IBS, the IBS- CM group demonstrated greater sensitivity to both thermal and visceral testing procedures. [ABSTRACT FROM AUTHOR]