Dementia

Dementia, classified in the DSM-5 as major neurocognitive disorder, is an acquired, usually progressive decline in one or more cognitive domains — memory, language, executive function, visuospatial skills, and judgment — significant enough to impair independence in everyday activities. It is not a single disease but a syndrome with many underlying causes, and it is distinct from the mild cognitive changes of normal aging.

Alzheimer disease is the most common cause of dementia, accounting for the majority of cases; it is characterized pathologically by amyloid-beta plaques and neurofibrillary tau tangles. Vascular dementia, caused by cumulative cerebrovascular damage, is usually cited as the next most common and classically shows stepwise decline, though some series place dementia with Lewy bodies ahead of it. Other important causes include Lewy body dementia (fluctuating cognition, visual hallucinations, parkinsonism), frontotemporal dementia (early personality and behavior change), and potentially reversible contributors such as hypothyroidism, vitamin B12 deficiency, depression (pseudodementia), and normal pressure hydrocephalus. Delirium differs from dementia by its acute onset, fluctuating course, and impaired attention.

Because dementia impairs judgment and financial decision-making, it matters outside medicine too: under FINRA Rule 2165, broker-dealers may place a temporary hold on disbursements when they reasonably believe a customer with diminished capacity is being financially exploited.

Dementia is tested widely. USMLE Step 1 emphasizes distinguishing the neurodegenerative dementias and their pathology; the NCLEX tests nursing care for older adults with dementia, including safety, communication, and differentiating dementia from delirium; and FINRA's SIE and Series 7 exams cover diminished capacity in the context of protecting vulnerable investors.