The impact of inflammatory bowel disease on dementia risk: a current systematic review and meta-analysis

Abstract

Emerging evidence indicates that inflammatory bowel disease (IBD) and dementia may share underlying pathological mechanisms and risk factors. However, the association between a prior IBD diagnosis and the subsequent risk of dementia remains largely unexplored. We conducted a comprehensive search of PubMed, Embase, and the Cochrane Library up to February 4, 2025, without language restrictions. Two reviewers independently extracted data and evaluated methodological quality and risk of bias. Observational studies comparing dementia risk in IBD and non-IBD populations were included. Pooled effect estimates for odds ratios (OR) were calculated using random-effects models. A total of 10 population-based studies, involving 7,895,339 participants (269,387 with IBD), were included. Meta-analysis of eight studies showed a significant association between IBD and dementia risk (OR 1.17, 95% CI: 1.08-1.27, P = 0.0001). However, IBD was not associated with an increased risk of Alzheimer's disease (AD) (OR 1.15, 95% CI: 0.98-1.36, P = 0.09). Stratified analysis by IBD type revealed a positive association between both ulcerative colitis (UC) and Crohn's disease (CD) and dementia risk (UC: OR 1.15, 95% CI: 1.05-1.25, P = 0.002, I² = 81%; CD: OR 1.26, 95% CI: 1.11-1.43, P = 0.0003, I² = 53%). This study identifies a significant correlation between IBD and dementia, suggesting that IBD patients have an elevated risk of developing dementia. However, current evidence is insufficient to establish a causal relationship. Further research should explore whether effective IBD treatments can mitigate this risk and elucidate the underlying pathophysiological mechanisms connecting these conditions.

Keywords: Dementia; Inflammatory bowel disease; Meta-analysis.

Fig. 1

PRISMA flow diagram for study selection. *Consider, if feasible to do so, reporting the number of records identified from each database or register searched (instead of the total number across all databases and/or registers). **If automation tools were used, indicate how many records were excluded by a human and how many were excluded by an automation tool.

Fig. 2

Forest plot for the risk of dementia in patients with inflammatory bowel disease.

Fig. 3

Forest plot for the risk of Alzheimer’s disease in patients with inflammatory bowel disease.

Fig. 4

Analysis of effect estimates based on study design for the risk of dementia in patients with inflammatory bowel disease.

Fig. 5

Forest plot for the risk of dementia in patients with ulcerative colitis.

Fig. 6

Forest plot for the risk of dementia in patients with Crohn’s disease.

Fig. 7

Funnel plot of Odds Ratio vs. Standard Error for log Odds Ratio using a random effect model to evaluate publication bias for the risk of dementia in patients with inflammatory bowel disease.