Description

Dementia refers to cognitive decline from previous level of performance in various cognitive domains (attention, executive function perceptual-motor, social cognition, 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 classifies dementias under neurocognitive disorders (major and mild) and 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

Epidemiology

• In patients age ≥65 years
  • AD: 5–10% (age 65 to 70 years); 25% (≥70 years)
  • VaD: 0.2% (age 65 to 70 years); up to 16% (≥70 years)
  • 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).

Risk Factors

• 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

General Prevention

• 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)
• Delirium
• Behavioral disturbances (agitation, aggression)
• Sleep disturbances