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- Alzheimer disease (AD) is the most common cause of dementia: 60–80% of those afflicted with dementia.
- AD is a progressive, irreversible, degenerative neurologic disease that results in neuron death.
- AD is the sixth leading cause of death in the United States (1).
- People ≥65 years with new AD live 4 to 8 years on average.
- AD is underdiagnosed (~50%), and many people diagnosed with AD are unaware of diagnosis (>50%).
- Economic burden in 2018: >$277 billion, projected at $1.1 trillion by 2050 (1)
- Dementia should be distinguished from:
- Age-related cognitive decline: lifelong process of changes in mental ability and memory; highly variable and part of normal aging
- Mild cognitive impairment (MCI): greater impairment than cognitive decline with individual and/or friends—family able to note impairment
- MCI: People are generally able to live independently from a cognitive perspective.
- MCI: affects 15–20% of those ≥65 years, with 32–38% developing dementia within 5 years
- AD diagnostic classification:
- Preclinical AD: research settings only at this time; no cognitive symptoms, AD biomarkers present
- MCI due to AD: if AD biomarkers present and not attributed to other causes; impairment often only in memory; no major social/occupational deficits
- Dementia due to AD:
- Early stage: memory impairment beyond MCI
- Middle stage: impairment in communication and response to environment
- Late stage: lose ability to appropriately recognize and respond to environment
- System affected: nervous
- Synonym(s): presenile dementia; senile dementia of the Alzheimer type
- “Welcome to Medicare” preventive visit (first 12 months of enrollment) and Medicare Annual Wellness Visit both require assessment of cognitive function.
- Even though the U.S. Preventive Services Task Force has a grade I (insufficient evidence) recommendation on asymptomatic routine screening for dementia
- Advanced care planning: Medicare reimbursable
- Predominant age: >65 years
- Incidence: females = males
- Prevalence: females > males, due to longer average lifespan in women
New cases of AD in the United States: 484,000/year (1)
- 65 to 75 years: 2 new cases per 1,000 people
- 75 to 84: 11 new cases per 1,000 people
- ≥85: 37 new cases per 1,000 people
>5.7 million in United States; ~44 million worldwide
- 14.4 million in United States by 2050
- 1 in 10 of those ≥65 years have AD dementia.
- 32% of those ≥85 years have AD dementia.
- ~200,000 in United States with early-onset AD (<65 years)
Etiology and Pathophysiology
- Progressive, irreversible disease where cognitive impairment worsens over time
- Caused by β-amyloid plaques outside of neurons and τ protein tangles inside of neurons, resulting in loss of connections between neurons and cell death
- Age, genetics, systemic disease, lifestyle behaviors, and other factors may influence AD progression.
- Autosomal dominant: <5% of AD, usually early onset (<65 years)
- Familial inheritance AD (nonautosomal dominant): 15–25% of AD, may be early- or late-age onset
- Sporadic, idiopathic: most of AD
- Nonmodifiable risk factors (1,2,3):
- Gender (due to longer lifespan in women)
- Family history
- Genetic mutations
- APOE-e4 gene variant: e4 heterozygous 2- to 3-fold risk; homozygous 10-fold risk (vs. e2 or e3)
- Cardiovascular disease–related risk factors (1,2):
- Hypertension (HTN) (especially in midlife years)
- Diabetes and impaired glucose processing
- Tobacco use
- Unhealthy diet
- Lack of physical activity/exercise
- Cerebrovascular (stroke) risks and injury
- Other potentially modifiable risk factors (1,2):
- Less years of formal education (<8th grade)
- Lack of continuous brain activity—learning
- Traumatic brain injuries: repetitive mild and moderate/severe
- Lack of social engagement
- Late-life depression
- Poor quality and inadequate sleep
- Hearing and vision deficits
- High alcohol consumption
- Possible environmental factors (e.g., pollution)
- Slowing/preventing cognitive decline, MCI, and AD are the top interest and concern of Americans ≥50 years.
- Evidence suggests that HTN management, increased physical activity, cognitive training may delay/prevent cognitive decline, MCI, and AD (2)[B].
- NSAIDs, estrogen, and vitamin E do NOT delay AD onset; insufficient evidence for statins (2)[A]
- Healthy lifestyle (e.g., exercise, sleep), potentially modifiable risk factors, may prevent or delay AD at the individual and population health level (2)[B].
- Actions to avert delirium during hospitalizations
- Treat psychiatric conditions (e.g., depression).
- Numerous medication can cause decreased cognition and delirium in the elderly.
Commonly Associated Conditions
- Down syndrome