APOE and Alzheimer disease: First, the population targeted in this study was patients with MCI; while our findings indicate that the AD-RAI can predict the risk of MCI progression to AD in those with the APOE-ε4 allele, the prediction of the risk of MCI or AD in APOE-ε4-positive healthy population is unknown, and it is possible that the AD-RAI differently predicts the risk of progression and cognitive decline in healthy individuals.