Fig. 1

Study overview. Step 1A represents the causal effects of gut microbiota on dementia. Step 1B represents the bi‑directional causal effects between gut microbiota and dementia. Step 2A represents the causal effects of cytokines on dementia. Step 2B represents the bi‑directional causal effects between cytokines and dementia. Step 3 represents the mediating analysis of cytokines in the pathway from the gut microbiota to dementia: path c was the total effect of gut microbiota on dementia; path b was the causal effect of cytokines on dementia; path a was the causal effect of gut microbiota on cytokines