How are Alzheimer disease and cerebrovascular disease related to cognitive decline in older adults?

Cognitive decline in older adults is frequently linked to Alzheimer disease and cerebrovascular disease, both of which are major contributors to dementia.12

Alzheimer Disease

Alzheimer disease is the most common cause of irreversible dementia, accounting for approximately two-thirds of cases in individuals over age 60. It is characterized by the progressive loss of neurons and the accumulation of specific brain lesions, including neuritic plaques (deposits of amyloid-beta protein) and neurofibrillary tangles (twisted tau protein fibers). These structural changes disrupt interneuronal communication by diminishing essential neurotransmitters, leading to a decline in memory, judgment, and social cognition.321

Cerebrovascular Disease

The second most common cause of dementia is vascular disease, often resulting from hypertension or a series of small strokes. This condition, known as vascular dementia, destroys brain tissue through restricted blood flow. Because neurons are highly sensitive to oxygen deficiency, conditions like arteriosclerosis that reduce blood supply can cause cognitive impairment and memory loss, even in the absence of primary neurodegenerative diseases.14