Dementia refers to cognitive decline from previous level of performance in various cognitive domains (attention, executive function perceptual-motor, social cognition, language, and memory) interfere significantly with ADLs in the absence 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)
    • Vascular dementia (VaD)
    • Lewy body dementia
    • Parkinson disease dementia
    • Frontotemporal dementia
    • Creutzfeldt-Jakob disease (CJD)
    • HIV dementia
    • Substance-/medication-induced neurocognitive disorder



  • In 2011, average annual incidence for AD was 0.4% in ages 65 to 74 years, 3.2% in ages 75 to 84 years, and 7.6% in ages ≥85 years.
  • Annual incidence of Alzheimer and other dementias expected to double by 2050


  • In patients aged ≥65 years
    • AD: 11.3% (5.3% in ages 65 to 74 years, 13.8% in ages 75 to 84 years, 34.6% in ages ≥85 years)
    • VaD: 1.6%
    • Other: 13%
  • Estimated 5 to 6 million Americans living with dementia
  • Expected to increase to 14 million by 2050

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% of AD is sporadic: APOE4 increases risk but full role unclear.
  • Familial/autosomal dominant AD accounts for <5% of AD: amyloid precursor protein (APP), presenilin-1 (PSEN-1), and presenilin-2 (PSEN-2).

Risk Factors

  • Age is the strongest factor.
  • Sex: female > male
  • Genetic predisposition
  • Hypertension: AD, VaD
  • Hypercholesterolemia: AD, VaD
  • Diabetes: VaD
  • Obesity: 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.
  • Maintain or increase physical activity and exercise.
  • Continue cognitively stimulating activities and social interactions.

Commonly Associated Conditions

  • Anxiety and major depression
  • Psychosis (delusions; delusions of persecution are common)
  • Delirium
  • Behavioral disturbances (agitation, aggression)
  • Sleep disturbances

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