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- Alzheimer disease (AD) is the most common cause of dementia in the elderly.
- Degenerative neurologic disease with progressive impairment in ≥2 years:
- Memory, executive function, attention, language, or visuospatial skills
- With significant interference in ability to function in work, home, or social interactions
- New diagnostic criteria released in 2011 emphasize full spectrum of disease (1)[A]:
- Preclinical AD (research purposes only: biomarkers present; subtle decline evident to patient but cognitive tests in “normal” range)
- Mild cognitive impairment (MCI): Social, occupational, and functional skills are preserved despite significant decline in cognition.
- Alzheimer dementia
- System(s) affected: nervous
- Synonym(s): presenile dementia; senile dementia of the Alzheimer type
Asymptomatic screening is not recommended.
- Predominant age: >65 years
- 2/3 females, 1/3 males in United States
1 in 8 Americans age >65 years (13%); ~50% at >85 years
>5.2 million in United States; >36 million worldwide
- 200,000 younger onset (<65 years)
Etiology and Pathophysiology
- Unknown but involves amyloid beta accumulation initially, then synaptic dysfunction, neurodegeneration, and eventual neuronal loss
- Age, genetics, systemic disease, behaviors (smoking), and other host factors may influence the response to amyloid beta and/or the pace of progression toward the clinical manifestations of AD.
- Positive family history in 50%, but 90% of AD is sporadic:
- APOE4 increases risk but full unclear
- Familial/autosomal dominant AD accounts for <5% AD:
- Amyloid precursor protein (APP), presenilin-1 (PS-1), and presenilin-2 (PS-2)
- Aging, family history, APOE4, Down syndrome
- HTN, cardiovascular, and carotid artery disease
- Smoking (2- to 4-fold increase)
- Head trauma
- NSAIDs, estrogen, and vitamin E do NOT delay AD; insufficient evidence for statins (2)[A]
- Intellectual challenge (puzzles) and regular physical exercise may offer preventive benefit.
- Control vascular risk factors (e.g., hypertension); lowering cholesterol may retard pathogenesis of AD.
- Ginkgo biloba may be beneficial for cognition but not activities of daily living.
- Physical activities and omega-3 fatty acids may help to prevent or delay cognitive decline.
- Ultrasound (US) may help to identify asymptomatic patients at increased risk with chronic brain hypoperfusion secondary to cardiovascular or carotid artery pathology.
Commonly Associated Conditions
- Down syndrome