Many studies indicate that miR‐21 can activate the PI3K/AKT signalling pathway in models of Alzheimer's disease and several malignant tumours.12, 13, 14 Other studies found that activation of the AKT/GSK‐3β signalling pathway attenuated oxidative stress and apoptosis in models of Alzheimer's disease, Parkinson's disease and intracerebral haemorrhage.15, 16, 17 More importantly, oxidative stress and apoptosis were common molecular abnormalities induced by TBI. This evidence concerns the gene AKT1 and Alzheimer disease.