Association between inflammatory bowel disease and Alzheimer’s disease: multivariable and bidirectional Mendelian randomisation analyses

Correspondence to Dr Ji-Feng Guo, Neurology, Xiangya Hospital Central South University, Changsha, Hunan 410011, China; guojifeng2003@163.com We read with interest the study by Zhang et al,1 showing that inflammatory bowel disease (IBD) was associated with increased risk of dementia, specifically Alzheimer’s disease (AD). [...]Guo et al2 used univariable MR to estimate causal roles of Ulcerative colitis (UC) and Crohn’s disease (CD) in AD, which may lead to horizontal pleiotropy due to a high degree of instrumental variable overlap between them. AD, Alzheimer’s disease; BMI, body mass index; CD, Crohn’s disease; IBD, inflammatory bowel disease; SNP, single-nucleotide polymorphism; UC, ulcerative colitis.