Description

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 disease (AD)
  • Vascular dementia (VaD)
  • Lewy body dementia
  • Parkinson disease dementia
  • Frontotemporal dementia
  • Creutzfeldt-Jakob disease (CJD)
  • HIV dementia
  • Substance-/medication-induced neurocognitive disorder

Epidemiology

Incidence

• 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

Prevalence

• In patients age ≥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

Genetics

• 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