RT Journal Article SR Electronic T1 Ranking microbiome variance in inflammatory bowel disease: a large longitudinal intercontinental study JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP 499 OP 510 DO 10.1136/gutjnl-2020-321106 VO 70 IS 3 A1 Adam G Clooney A1 Julia Eckenberger A1 Emilio Laserna-Mendieta A1 Kathryn A Sexton A1 Matthew T Bernstein A1 Kathy Vagianos A1 Michael Sargent A1 Feargal J Ryan A1 Carthage Moran A1 Donal Sheehan A1 Roy D Sleator A1 Laura E Targownik A1 Charles N Bernstein A1 Fergus Shanahan A1 Marcus J Claesson YR 2021 UL http://gut.bmj.com/content/70/3/499.abstract AB Objective The microbiome contributes to the pathogenesis of inflammatory bowel disease (IBD) but the relative contribution of different lifestyle and environmental factors to the compositional variability of the gut microbiota is unclear.Design Here, we rank the size effect of disease activity, medications, diet and geographic location of the faecal microbiota composition (16S rRNA gene sequencing) in patients with Crohn’s disease (CD; n=303), ulcerative colitis (UC; n = 228) and controls (n=161), followed longitudinally (at three time points with 16 weeks intervals).Results Reduced microbiota diversity but increased variability was confirmed in CD and UC compared with controls. Significant compositional differences between diseases, particularly CD, and controls were evident. Longitudinal analyses revealed reduced temporal microbiota stability in IBD, particularly in patients with changes in disease activity. Machine learning separated disease from controls, and active from inactive disease, when consecutive time points were modelled. Geographic location accounted for most of the microbiota variance, second to the presence or absence of CD, followed by history of surgical resection, alcohol consumption and UC diagnosis, medications and diet with most (90.3%) of the compositional variance stochastic or unexplained.Conclusion The popular concept of precision medicine and rational design of any therapeutic manipulation of the microbiota will have to contend not only with the heterogeneity of the host response, but also with widely differing lifestyles and with much variance still unaccounted for.Data are available on reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information. Sequence data are available at NCBI SRA PRJNA414072.