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- DSM-5 classifies dementias under neurocognitive disorders (major and mild).
- Evidence of cognitive decline from previous level of performance in one of cognitive domains (attention, executive function, learning, and memory). The cognitive deficits interfere significantly with ADLs (for major only) and do not occur exclusively in the context of delirium or any other mental disorder.
- DSM-5 specifies the cause of neurocognitive decline secondary to the following:
- Alzheimer dementia (AD)
- Progressive cognitive decline; most common age >65 years
- Vascular dementia (VaD)
- Usually correlated with a cerebrovascular event and/or cerebrovascular disease
- Stepwise deterioration with periods of clinical plateaus
- Lewy body dementia
- Fluctuating cognition associated with parkinsonism, hallucinations and delusions, gait difficulties, and falls
- Frontotemporal dementia
- Language difficulties, personality changes, and behavioral disturbances
- Creutzfeldt-Jakob disease (CJD)
- Very rare; rapid onset
- HIV dementia
- Substance-/medication-induced neurocognitive disorder
- Alzheimer dementia (AD)
- In patients age ≥71 years
- AD: 5–10% up to 25% after 7th decade of life
- VaD: 17%
- Other: 13%
- Estimated 5.4 million Americans had AD in 2010.
- 5 million >65 years of age; 200,000 <65 years
- Prevalence expected to double by 2030.
Etiology and Pathophysiology
- AD: involves β-amyloid protein accumulation and/or neurofibrillary tangles (NFTs), synaptic dysfunction, neurodegeneration, and eventual neuronal loss
- Age, genetics, systemic disease, smoking, and other host factors may influence the β-amyloid accumulation and/or the pace of progression toward the clinical manifestations of AD.
- VaD: cerebral atherosclerosis/emboli with clinical/subclinical infarcts
- AD: Positive family history in 50%, but 90% AD is sporadic: APOE4 increases risk but full role unclear.
- Familial/autosomal dominant AD accounts for <5% AD: amyloid precursor protein (APP), presenilin-1 (PSEN-1), and presenilin-2 (PSEN-2).
- Age; sex: female > male
- Genetic predisposition
- Hypertension: AD; VaD
- Hypercholesterolemia: AD; VaD
- Diabetes: VaD
- Cigarette smoking: VaD
- Endocrine/metabolic abnormalities: hypothyroidism, Cushing syndrome; thiamine and vitamin B12 deficiency
- Chronic alcoholism, other drugs
- Lower educational status
- Head injury early in life
- Sedentary lifestyle
- Treat reversible causes of dementia, such as drug-induced, alcohol-induced, and vitamin deficiencies.
- Treat hypertension, hypercholesterolemia, and diabetes.
- No evidence for statins (or any other specific medication) to prevent onset of dementia (1)[A]
- BP control and low-dose aspirin may prevent or lessen cognitive decline in VaD.
Commonly Associated Conditions
- Anxiety and major depression
- Psychosis (delusions; delusions of persecution are common)
- Behavioral disturbances (agitation, aggression)
- Sleep disturbances