Can early gut microbiota screening reduce the incidence of cognitive impairment? A Mendelian randomization study

Background: Gastrointestinal symptoms are now detected early in the clinical course of many dementia patients, and studies of the microbiome-gut-brain axis have confirmed bidirectional interactions between the gut and the brain. However, the causal relationship between gut microbiota and cognitive impairment has not been fully established. Therefore, this study conducted a bidirectional Mendelian randomization study to elucidate the potential causal relationship of gut microbiota to cognitive impairment. Objective: Using Mendelian randomization to identify gut flora with a genetic causal effect on the development of cognitive impairment. Methods: This study utilized publicly available genome-wide association study summary data to perform MR analysis, with gut microbiota as the exposure and various cognitive function indicators as well as scores for Alzheimer's disease as outcomes. This study selected single nucleotide polymorphisms as instrumental variables based on p-values, F-statistics, and r². Bidirectional Mendelian randomization was conducted using methods such as inverse variance weighted, MR-Egger, simple mode, and weighted mode to assess the causal relationship. Concurrently, this study carried out Cochran's Q test, MR-Egger intercept test, and leave-one-out analysis to identify potential heterogeneity and horizontal pleiotropy. Results: This study identified a total of 31 gut microbes that have a causal relationship with cognitive impairment, which include 1 phylum, 4 classes, 3 orders, 2 families, and 21 genera. Conclusions: This study unveiled specific gut microbiota associated with cognitive impairment, offering new insights and approaches for the prevention and treatment of cognitive impairment through gut microbiota such as Bifidobacterium and Ruminococcus gnavus group.