Summary Background Inflammatory bowel disease (IBD) may be associated with increased dementia risk, but the literature is conflicting. Aim To investigate dementia risk in patients with IBD. Methods We conducted a nationwide population‐based cohort study in Denmark (1977–2018) including all patients with incident IBD matched with up to 10 general population comparators without IBD by sex, year of birth and region of residence. We calculated cumulative incidence proportions (CIPs) of dementia treating death as a competing risk, and adjusted hazard ratios (HRs) comparing IBD patients with matched comparisons. In a nested case–control analysis, we investigated the impact of IBD severity, steroid use, colorectal and small bowel surgery, and healthcare system contacts on dementia risk. Results Of 88,985 patients with IBD (69.6% with ulcerative colitis [UC], 30.4% with Crohn's disease [CD]) and 884,108 comparisons, 2076 patients (78.1% with UC) and 23,011 comparisons (76.6% UC comparisons) developed dementia. The 40‐year CIP of all‐cause dementia was 7.2% for UC patients and 5.8% for CD patients. UC patients had a slightly increased HR of all‐cause dementia (HR = 1.07 [95% confidence interval (CI): 1.01;1.12]) and Alzheimer's disease (HR = 1.10 [95% CI: 1.01–1.19]). CD patients had an increased HR of all‐cause dementia (HR = 1.15 [95% CI: 1.05–1.27]) and frontotemporal dementia (HR = 2.70 [95% CI: 1.44–5.05]). Dementia in IBD patients was associated with frequent healthcare system contacts. Conclusions UC and CD are associated with slightly increased all‐cause dementia risk, particularly frontotemporal dementia in CD patients. Frequent healthcare system contacts by patients with IBD and detection bias may play a role in the association.

Background Venous thromboembolism (VTE) may be a harbinger of cancer in the general population. Patients with kidney disease have an a priori increased VTE risk. However, it remains unknown how a VTE affects subsequent cancer risk in these patients. Objectives To examine the cancer risk in patients with kidney disease following a VTE. Methods We conducted a nationwide population-based cohort study in Denmark (1996–2017), including all VTE patients with a diagnosis of kidney disease. We calculated absolute risks of cancer (accounting for competing risk of death) and age-, sex-, and calendar-period standardized incidence ratios (SIRs) comparing the observed cancer incidence with national cancer incidence rates and cancer incidence rates of VTE patients without kidney disease. Results We followed 3,362 VTE patients with kidney disease (45.9% females) for a median follow-up time of 2.4 years (interquartile range: 0.6–5.4). During follow-up, 464 patients were diagnosed with cancer, of whom 169 (36.4%) were diagnosed within the first year. The 1-year absolute risk of any cancer was 5.0% (95% confidence interval [CI]: 4.3–5.8), with a SIR of 2.9 (95% CI: 2.5–3.4) when compared with the general population, and 2.0 (95% CI: 1.8–2.4) when compared with VTE patients without kidney disease. During subsequent years of follow-up, the SIRs declined to 1.5 (95% CI: 1.3–1.6) when compared with the general population, and 1.1 (95% CI: 0.9–1.2) compared with VTE patients without kidney disease. Conclusions Patients with hospital-diagnosed kidney disease have increased cancer risk after VTE, especially within the first year following the VTE diagnosis.

LINKED CONTENT This article is linked to Rønnow Sand et al papers. To view these articles, visit https://doi.org/10.1111/apt.17119 and https://doi.org/10.1111/apt.17234