The goal of this clinical trial is to learn about the effects of social isolation and social interaction on the risk of dementia progression and brain function in SCD

1. To explore the association between social isolation and lonely SCD populations and the occurrence and progression of MCI and AD through cross-sectional studies, cohort studies and randomized controlled trials of SCD;
2. To clarify the correlation between different carrier states, resting brain function connectivity characteristics, and dual-task walking ability of APOEε4 allele and the progression of SCD to MCI and AD during the cognitive progress of people with SCD affected by social isolation;
3. Establish a predictive model of cognitive decline from SCD to MCI and AD, and apply it to the SCD population to carry out individualized interventions;
4. Confirm the protective effect of social interaction on cognitive level and brain function in SCD patients.

1. to explore the impact of social isolation on the risk of progression to MCI or AD in the SCD population.

1. A cohort study design was enrolled in the SCD population, assess the degree of social isolation, and analyze the impact of social isolation, an exposure factor, on the progression of SCD patients to MCI or AD by collecting 3-5 years follow-up data;
2. To analyze the interaction between the degree of social isolation of SCD patients and the connectivity characteristics of executive control, default network, and language network in the brain functional network.

2. the predictive effects of APOE-ε4 genotype, degree of social isolation, loneliness, and dual-task walking ability on the risk of SCD progression to MCI and AD in SCD population.

1. Using data from a cohort study, a prediction model of the SCD population with APOE-ε4 genotype, degree of social isolation, loneliness, dual-task walking parameter, degree of executive-control brain network connectivity, and degree of depression was developed to predict the risk of SCD progression to MCI and AD;
2. Use the above prediction model to apply to the clinic for prognostic prediction and individualized risk factor control in the SCD population.

Inclusion Criteria:

• SCD

  1. Self-perceived continuous cognitive decline compared with the previous normal state, and is not related to acute events;
  2. After adjustment for age, gender, and years of education, the standard cognitive test is normal, or the diagnostic criteria for MCI are not met;
  3. Selected candidates can sign the informed consent form themselves.

Exclusion Criteria:

• (a) Aged under 45 years or older than 85 years; (b) Vascular dementia or other central nervous system diseases; (c) Hachinski Ischemic Scale score > 4 points; (d); Unable to complete neuropsychological tests (e.g., blindness, deafness, severe language impairment); (e) Drug abuse or alcohol dependency within the last 6 months; (f) Current participation in other cognition studies; (g) Severe diabetes mellitus, or severe cardiovascular disease, cerebrovascular disease, liver diseases, kidney diseases, psychiatric disorders; (h) Contraindications to imaging techniques: claustrophobia, metallic implants (e.g., intracranial metal clips), electronic devices (e.g., cardiac pacemakers)

Subjects were grouped as SCD when they reported cognitive decline compared with a previous state, whereas neuropsychological battery and other objective investigations (adjusted age, gender, and education) were normal, and criteria for MCI, dementia, or any other neurologic or psychiatric diseases that potentially cause cognitive complaints were not met.