This is an observational study aimed at understanding the cognitive, functional, and behavioral characteristics of Chinese patients with cognitive impairment, exploring the underlying mechanisms, and providing evidence for early diagnosis, treatment, and care of cognitive disorders including dementia.

Eligible participants will undergo a series of assessments and examinations, including cognitive and memory scale tests, routine blood tests, ApoE genetic testing, cerebrospinal fluid testing, brain MRI, functional MRI, and FDG-PET/AV45-PET scans when necessary. Additional samples such as saliva, nasal secretions, and stool may also be collected. Most evaluations are provided free of charge to support diagnosis and treatment guidance.

Participation is voluntary. All personal information and research data will be kept confidential. Potential benefits include access to expert clinical care and free cognitive assessments for disease evaluation. Possible inconveniences include time commitment and temporary discomfort during examinations; medical support will be provided if needed.

Inclusion Criteria:

• Participants with clinically diagnosed cognitive impairment. Patients with clinically diagnosed Parkinson's disease. Healthy control participants.

Exclusion Criteria:

• Central nervous system infection, head trauma, epilepsy, multiple sclerosis, or other major neurological disorders.

Malignant tumors. Family history of genetic disorders.

Participants were recruited from Yantai Yuhuangding Hospital, Yantai, Shandong Province, China.

IPD will not be shared due to privacy regulations, ethical requirements, and limitations specified in the informed consent document.