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Irritable bowel syndrome (IBS) is currently defined as a disorder of the gut-brain axis, characterized by abdominal pain related to defecation and changes in consistency and/or frequency of bowel movements. Both central and gut-specific neuronal mechanisms play a role in its pathophysiology. The current classification for IBS often overlooks medical/psychiatric comorbidities and diet or lifestyle patterns that may drive a patient's unique IBS phenotype. This pattern is further propagated in IBS treatment, with FDA-approved drugs only targeting pain and bowel dysfunction.

In a study recently published in , Byale et al. used the Mayo Clinic Biobank to survey patients using a questionnaire incorporating Rome III criteria for IBS. They identified 4,021 IBS patients (mean age 64 years, 75% women) after applying exclusion criteria. Factors associated with IBS (lifestyle/diet behaviors, weekly leisure activity score, and comorbid conditions) were determined, and latent class analysis, a model-based clustering, was performed on IBS cases.

Using 26 variables separating cases from controls, the optimum clustering revealed seven latent clusters characterized by perceived health impairment (moderate or severe), prevalence of psychoneurological diagnoses (psychoneurological or psychiatric or neurological), and bowel dysfunction (diarrhea or constipation predominance). While health impairment clusters reported more pain, with the "severe" cluster also having more psychiatric comorbidities, the psychoneurological clusters had a unique mix of psychiatric and neurological conditions, but were not enriched for pain, bowel dysfunction, or perceived impairment in health. The last two clusters were characterized by bowel dysfunction but had lower-than-average perceived health impairment or other comorbidities. More subtle lifestyle variables such as dietary fiber intake, sugar and fat intake, smoking, and alcohol use were also observed as trends within the different clusters.

Clinically, the findings in this study are very useful for stratifying a complex IBS patient population in which disease pathophysiology and expression are not a one-size-fits-all model. Through classifying patients into clusters, we can focus on treating the underlying lifestyle, medical, or neuropsychiatric factors that may be driving their symptoms. The differing prevalence of pain and lifestyle impairment through the clusters also brings into question the FDA's criteria for approving IBS therapies and opens the door for a more individualized and inclusive approach to IBS treatment. Last but not least, this study opens the door for more robust prospective clinical trials focusing on a diverse (race, age, gender, socioeconomic status) patient population to improve IBS care.

Arushi Kohli, MD, is a gastroenterology fellow at Boston Medical Center.

You can read an interview with the senior study author here, and the abstract of the study here.