The main purpose of this study is to investigate the safety and efficacy of Yi-Zhi-An-Shen Granules in participants with amnestic mild cognitive impairment (aMCI).

The investigators performed a randomized, placebo-controlled, double-blind study on evaluating effect of Yi-Zhi-An-Shen Granules on cognition, sleep quality, and gut microbiome of older adults with amnestic mild cognitive impairment (aMCI). The investigators plan to involve 80 cases for observation in 2 years (40 cases for each group), expecting that cognition and sleep quality of aMCI patients can be improved by Yi-Zhi-An-Shen Granules versus placebo, and discussing the differences between individuals with aMCI and ones with normal cognition, also investigating whether this Chinese medicine compound can regulate gut microbiome of older individuals with aMCI.

Inclusion Criteria:

• Subject has assigned informed consent to participate in the study and continues to give willing consent for participation
• Age from 60 to 85 years with a diagnosis of aMCI
• Educational level of at least 6 years
• Availability of a "study partner" who can assist in completing rating scales for the duration of the study
• Cognitive complaints reported by the subject and confirmed by the "study partner"
• Clinical Dementia Rating (CDR) global score of 0.5, and memory item score of 0.5
• Mini-mental state examination (MMSE) score of 24-30
• Diagnostic and Statistical Manual of Mental Disorders, Version 5 (DSM-V) criteria of dementia not fulfilled

Exclusion Criteria:

• Has been previously enrolled in this study and received the investigational product
• Has received an investigational product within 30 days prior to screening
• Has received disease-modifying therapy
• Has a known allergy to the study drug or any of its constituents
• Has a history of alcohol abuse or alcohol dependency in the 3 years prior to study entry, or is an alcoholic or drug addict, as determined by the investigator
• Has ongoing clinically significant (as judged by the investigator), metabolic or any other disease that could currently cause impaired memory (e.g., untreated thyroid disease, vitamin or other nutritional deficiencies, chronic kidney, or liver disease)
• Memory impairment that can be attributed to a disease or condition other than an early phase neurodegenerative syndrome
• Has a parkinsonian movement disorder
• Use of psychoactive medications that would affect the subject's ability to reliably perform neurocognitive testing or create uncertainty in distinguishing between the effects of the psychoactive medication and the subject's underlying cognitive impairment (e.g., benzodiazepines, sedatives, antipsychotics)
• History of major recurrent depressive disorder (DSM-V) within the last 5 years prior to screening
• Has a brain tumor or other intracranial lesion, a disturbance of cerebral spinal fluid circulation (e.g., normal pressure hydrocephalus), and/or a significant history of head trauma or brain surgery
• Has signs of major cerebrovascular disease, with score of modified Hachinski Ischemia Score (mHIS) at more than 4, or as verified by medical history and/or brain MRI or CT
• Has severe visual or hearing impairments that cannot cooperate with examinations
• Has severe digestive system diseases
• Has received antibiotics within 60 days prior to screening