Characterization and impact of disorders of gut-brain interaction: a national and international epidemiological project

Abstract

Disorders of gut-brain interaction (DGBI) are highly prevalent conditions, characterized by chronic or recurrent gastrointestinal (GI) symptoms. DGBI significantly impacts quality of life (QoL) and healthcare utilization, leading to high socioeconomic costs. Understanding the importance of these factors is key in optimizing resource allocation and management, highlighting an unmet need for a comprehensive report on these aspects of DGBI. This thesis aimed to enhance the knowledge of prevalence, characteristics, impact and healthcare utilization in several DGBI in international and national populations. In study I we report a high and stable positive predictive value of ICD-10 codes for irritable bowel syndrome (IBS) in the Swedish National Patient Register, supporting its use for identifying IBS patients, and provide guidance for future study planning and interpretation. In study II, we report an increased rate of doctor visits due to GI and other health problems, increased use of medication and excess abdominal surgeries amongst those fulfilling the criteria for IBS in the general population, and that frequent abdominal bloating influence the consulting behavior. Additionally, we found a possible sex-dependent bias in doctors when diagnosing IBS. Study III found that DGBI are common in the Swedish general population, with prevalence rates and impact similar to those in other countries. Bothersome GI symptoms and overlapping DGBI increased healthcare utilization. Our findings also provide support for the importance of non-GI somatic and psychological symptoms for consulting behaviors in DGBI. In study IV we report that functional bowel disorders (FBD) affect one in three adults worldwide, with minimal differences across regions. All FBD impact symptom burden, QoL and healthcare utilization, most pronounced in IBS and opioid-induced constipation. The major contributor to the decrease in IBS prevalence, comparing Rome IV vs. Rome III criteria, was the change in symptom frequency threshold for abdominal pain. We also report that less strict IBS definitions still identified a clinically relevant population. In summary, this thesis provides several epidemiolocal insights of value for current clinical practice, management guidelines, and for future research, including the refinement of diagnostic criteria.