The prevalence of Mild Cognitive Impairment (MCI) is about 15%-17%. 10%-15% of MCI progresses to Alzheimer's disease (AD) every year. The annual incidence of MCI in the normal elderly is about 1%. is the key and difficult points in AD research. Except expensive brain β amyloid plaque imaging, few breakthroughs of early diagnosis technology of MCI due to AD can be made to facilitate clinical application. The purpose of this program is to study the reliability and validity of plasma miRNAs for early diagnosis of MCI due to AD. The clinical diagnosis of AD and MCI due to AD are according to the National Institute of Aging and the Alzheimer's Disease Association (NIA-AA) diagnostic criteria in 2011. [18F]-AV-45 plaque imaging is used to be golden criteria for the diagnosis of AD and MCI due to AD. Next, a pilot intervention study on APP/PS1 transgenic mice will be promoted based on miRNAs gene regulation.

Inclusion Criteria:

• 2011 NIA-AA criteria of MCI due to AD or AD

Exclusion Criteria:

• Non AD dementia

After the study is finished.

In this study, the clinical researchers are responsible for the clinical diagnosis of the subjects and the diagnosis of senile plaques. The biological sample testing agency receives the blind coded samples. After the repeated testing, the data are handed over to the blind statistical experts for statistics. The statistical experts only obtain the grouping information and biological sample data, but do not know the specific diagnosis grouping, so as to ensure the accuracy of the statistical results. The results were analyzed by the researchers after the completion of the statistics.