Investigating Neurocognitive Disorders Epidemiology

1. Cognitively Healthy Individuals INCLUSION CRITERIA * Demonstrate normal cognitive function within the expected range on objective cognitive tests. * Proficient in speaking and understanding Thai without the need for a translator to participate. EXCLUSION CRITERIA * Significant neurological or uncontrolled psychiatric illness. * Significant unstable systemic condition or end-stage organ failure that affects study participation. 2. Mild Cognitive Impairment INCLUSION CRITERIA * Display impaired/abnormal performance on objective cognitive tests. * Does not meet criteria for dementia per NIA-AA (or major neurocognitive disorder per DSM-5). * Proficient in speaking and understanding Thai without the need for a translator to participate. EXCLUSION CRITERIA * Significant neurological or uncontrolled psychiatric illness. * Significant unstable systemic condition or end-stage organ failure that affects study participation. 3. Late Onset Dementia INCLUSION CRITERIA * Display impaired/abnormal performance on objective cognitive tests. * Meets criteria for dementia per NIA-AA (or major neurocognitive disorder per DSM-5), including dementia due to Alzheimer's disease or other causes. * Begins to experience symptoms, identified by the physician as a part of dementia continuum, occurring after the age of 65. * Proficient in speaking and understanding Thai without the need for a translator to participate. EXCLUSION CRITERIA * Significant neurological or uncontrolled psychiatric illness. * Significant unstable systemic condition or end-stage organ failure that affects study participation. 4. Early Onset Dementia INCLUSION CRITERIA * Display impaired/abnormal performance on objective cognitive tests. * Meets criteria for dementia per NIA-AA (or major neurocognitive disorder per DSM-5), including dementia due to Alzheimer's disease or other causes. * Begins to experience symptoms, identified by the physician as a part of dementia continuum, occurring before the age of 65. * Proficient in speaking and understanding Thai without the need for a translator to participate. EXCLUSION CRITERIA * Significant neurological or uncontrolled psychiatric illness. * Significant unstable systemic condition or end-stage organ failure that affects study participation.