Alzheimer Disease

Alzheimer Disease is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • 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

Geriatric Considerations
Asymptomatic screening is not recommended.

Epidemiology

  • Predominant age: >65 years
  • 2/3 females, 1/3 males in United States

Incidence
1 in 8 Americans age >65 years (13%); ~50% at >85 years

Prevalence

>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.

Genetics
  • 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)

Risk Factors

  • Aging, family history, APOE4, Down syndrome
  • HTN, cardiovascular, and carotid artery disease
  • Smoking (2- to 4-fold increase)
  • Head trauma

General Prevention

  • 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
  • Depression

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Citation

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TY - ELEC T1 - Alzheimer Disease ID - 116014 Y1 - 2019 PB - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116014/all/Alzheimer_Disease ER -