MO508: Estimated Glomerular Filtration Rate and the Risk of Inflammatory Bowel Disease in Adults: A Swedish Population-Based Study

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Abstract BACKGROUND AND AIMS Chronic kidney disease (CKD) and inflammatory bowel disease (IBD) share many risk factors. While kidney complications are seen in 4%–23% of patients with longstanding IBD, it is unknown whether low kidney function may predispose to developing IBD. METHOD We analyzed the association between estimated glomerular filtration rate (eGFR) and the risk of being diagnosed with IBD among 1 612 160 adults without prior IBD history who accessed healthcare in Stockholm during 2006–18. We categorized eGFR into five groups: <30, 30–59, 60–89, 90–104, 105 + mL/min/1.73m2 with 90–104 being the reference group. Flexible parametric survival models with stepwise adjustments and piecewise linear splines were used to investigate the association between eGFR, IBD and IBD-subtypes (Crohn's disease, ulcerative colitis and IBD unclassified). IBD cases were identified by two or more records with an IBD diagnosis. Subgroup analyses explored the consistency of the associations between age strata, sex, background education and the presence of selected comorbidities. To explore the possibility of detection bias and reverse causation, we estimated IBD risks from the first year after baseline eGFR. RESULTS We detected 9663 new cases of IBD (Crohn's disease: n = 3299 and ulcerative colitis: n = 5072), over a median follow-up of 9 years. Linear splines suggested the association between eGFR and IBD to be J-shaped, with higher IBD risk at both eGFR extremes. After multivariable adjustment and compared with eGFR 90–104 mL/min/1.73 m2 lower eGFR strata were associated with higher IBD risk {adjusted hazard ratio (HR), 1.14; [95% confidence interval (95% CI) 0.99–1.32] for eGFR = 30–59 mL/min and 1.63; 1.14–2.33 for eGFR <30 mL/min}. This association was stronger in magnitude for Crohn's disease, with an HR of 1.32 (1.03–1.71) for eGFR = 30–59 mL/min and 2.22 (1.24–3.97) for eGFR <30 mL/min. Subgroup analyses showed consistency across age, education categories, presence of diabetes and of CVD, but suggested that the association between low eGFR and IBD was stronger in women and in the absence of hypertension (P for interaction <.05). Associations were slightly attenuated after excluding IBD cases during the first year of follow-up, indicating the presence of detection bias and/or reverse causation. CONCLUSION We observed an association between decreased eGFR and the risk of developing IBD, which was stronger in magnitude for Crohn's disease, but that could be partly explained by bias.