This study investigates the causal relationships between gut microbiota, cytokines, and five types of dementia (Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, vascular dementia, and Parkinson's disease dementia) using Mendelian randomization (MR). The gut microbiota and cytokines were identified from large-scale genome-wide association studies (GWAS) summary data. The main statistical method used was inverse variance weighting (IVW). The study found 20 positive and 16 negative causal effects between genetic liability in the gut microbiota and dementia, and five positive and four negative causal effects between cytokines and dementia. However, cytokines did not act as mediating factors in the pathway from gut microbiota to dementia. The study concludes that gut microbiota and cytokines are causally associated with dementia, but cytokines do not mediate the relationship between gut microbiota and dementia.This study investigates the causal relationships between gut microbiota, cytokines, and five types of dementia (Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, vascular dementia, and Parkinson's disease dementia) using Mendelian randomization (MR). The gut microbiota and cytokines were identified from large-scale genome-wide association studies (GWAS) summary data. The main statistical method used was inverse variance weighting (IVW). The study found 20 positive and 16 negative causal effects between genetic liability in the gut microbiota and dementia, and five positive and four negative causal effects between cytokines and dementia. However, cytokines did not act as mediating factors in the pathway from gut microbiota to dementia. The study concludes that gut microbiota and cytokines are causally associated with dementia, but cytokines do not mediate the relationship between gut microbiota and dementia.