Irritable Bowel Syndrome in Teens
While these findings provide further evidence of central pain mechanisms in IBS, researchers of a new study discovered interesting novelties—including normal pain tolerance—that may lend more knowledge to the pathophysiology of chronic pain in IBS patients.1,2
Norwegian researchers conducted extensive physical examinations of nearly a 1,000 girls and boys between the age of 15 to 17 years, as well as administered a questionnaire to measure symptomatic scores in psychological distress and comorbid chronic pain levels.1
Of the entire patient population, 8.2% met the researchers' definition for IBS, they reported in a recent article in The Journal of Pain.1 Chronic abdominal pain was unanimous in IBS cases, where moderate pain was reported the most often (51.9%). Mild and severe pain were reported less often, 26% and 22.1%, respectively.
IBS patients had noticeably lower thresholds for heat and pressure pain when compared to controls. While IBS patients with mild pain did not have any noticeable differences in their heat pain thresholds when compared to controls, IBS patients with moderate and severe pain scores had pain thresholds decreased by 1.0 to 1.6 degrees Celsius, respectively.
According to lead author Niklas Stabell, MD, from the University of Tromsø in Tromsø, Norway, these results could be evidence of a dose-response relationship between chronic abdominal pain and pain thresholds, where severe chronic pain influences a much lower pain threshold.
Pain tolerance, on the other hand, showed no discernible differences between the IBS adolescent patients and controls, a surprising finding given that previous studies of adult IBS cases reported lower pain tolerances.3-4 Last year, Dr. Stabell’s group conducted a study of adult IBS patients and found similar results.5 The question arises: Why do adolescent IBS cases show normal tolerance levels in contrast to adults?
Dr. Stabell and colleagues suggested that pain tolerance in IBS patients experiences an "age effect," where pain tolerance alters after substantial time with IBS symptoms. This would explain why adult IBS patients have lower pain tolerance while adolescents do not.
"As far as we know, no prospective studies of chronic pain have investigated whether pain tolerance is related to the duration of pain symptoms," noted the researchers.
"One could speculate that persistence of chronic visceral pain results in neuroplastic remodeling of the brain6 and that such remodeling is associated with reduced pain tolerance."
Sex Bias Also Seen
Furthermore, prior to Dr. Stabell's latest study, researchers never examined the possible sex differences in heat and pressure pain thresholds in a pediatric patient group. In the current study, females with IBS had noticeably more sensitive bias with their pain thresholds, following the trend of research seen in adult cases.7,8 Some research suggests that this dimorphism emerges and grows in prevalence during puberty.7
There may be limitations to this study's validity, however. The IBS cases were reported solely through self-reported data, which means a lack of clinical diagnoses could have caused inaccurate results. While many organic diseases can be misclassified as IBS, pediatric patients with abdominal pain commonly have gastrointestinal disorders, IBS being the most common one.9-11 So, the prevalence of IBS symptoms limits this risk.
Regardless, Dr. Stabell's study featured robust statistical analysis, a high response rate, and significant population data. Moreover, their findings of lower pain thresholds in adolescent IBS cases provides evidence of widespread hyperalgesia occurring in the pediatric IBS population and establishes additional support for the theory of central pain sensitization in IBS patients.2,12
The Northern Norway Regional Health Authority funded the study. None of the researchers reported any conflicts of interest.