The mechanism of AD to POCD may be associated with enhanced inflammation and oxidative stress, inducing neuronal apoptosis, synaptic dysfunction, central cholinergic damage, and accelerated tau protein phosphorylation, and we also found that the brain‐intestinal axis plays an important role in a variety of miRNA involved in the development of diseases and the multifactorial cascade reaction of these factors causes POCD (Figure 1). The gene discussed is MAPT; the disease is Alzheimer disease.