Gut microbiota are more strongly associated with impairments in health-related quality of life than disease activity in inflammatory bowel disease

Background and Aims: Inflammatory bowel disease (IBD) impacts health-related quality of life (HRQoL). Gut dysbiosis in IBD is common and may contribute to this observation. The aims of this study were to measure HRQoL and its association with clinical and microbial features in patients with IBD and healthy controls (HC). Methods: Fecal and oral samples, demographics, SF-36 and IBDQ-32 surveys were collected at baseline from patients with Crohn’s disease (CD), ulcerative colitis (UC) and HCs enrolled in The Australian IBD Microbiome Study. Samples underwent 16S rRNA sequencing. Associations between HRQoL variables and alpha diversity, beta diversity and microbial taxa abundance were measured using R. Results: 751 participants (305 HC, 232 CD, 214 UC) were included. HRQoL was lower in IBD participants compared to HCs using the SF-36 (physical component summary 51.6 vs. 55.7, p < 0.0001 and mental component summary score 45.1 vs. 52.2, p < 0.001). Despite high rates of remission, impaired IBD-HRQoL (IBDQ-32 score <170) was common in CD (42%) and UC (41%). Patients with impaired IBDQ-32 scores demonstrated lower alpha diversity (Chao1 155.2 vs. 172.4, p = 0.015) and distinct beta diversity (R 2 = 0.003, p = 0.019) compared to those with preserved IBD-HRQoL. 62 genera were associated with at least one HRQoL measure in both UC and CD patients. The number and strength of associations between genera and HRQoL measures outweighed microbial associations with clinical and biochemical activity. Conclusion: Alterations in gut microbiota are associated with HRQoL outcomes in patients with IBD and healthy controls .