Introduction to Dementia

Dementia is a progressive neurocognitive decline of sufficient magnitude to interfere with normal social or occupational functions, or with usual daily activities. It is a broad diagnostic category that includes Alzheimer's disease, Lewy Body dementia, frontotemporal dementia, vascular dementia, Parkinson's disease, and Creutzfeldt–Jakob disease (among many others).

About 35% of dementia is attributable to nine modifiable factors across the lifespan.[1] These factors include: education, midlife hypertension, midlife obesity, hearing loss, late-life depression, diabetes, physical inactivity, smoking, and social isolation.[2]

The World Health Organization (WHO) Dementia Prevention Guidelines recommends the following to reduce the risk of dementia:[3]

  1. Physical exercise (there is some conflicting data[4])
  2. Tobacco cessation
  3. Reduce harmful drinking
  4. Lose excess weight in midlife
  5. Adhere to healthy diet (a Mediterranean-style diet may reduce dementia risk)
  6. Cognitive training can be tried for adults with normal cognition or mild impairment (but the quality of evidence to support this is low)
  7. Social participation and support are important throughout life (but limited evidence to support)
  8. Hypertension, diabetes, and depression should be managed according to existing guidelines (but it's not clear whether doing so will specifically lower dementia risk)

Vitamins B and E, polyunsaturated fatty acids, and multivitamins are not recommended for risk reduction of dementia.[5]

Common Dementia Subtypes and Presentation

Subtype Percent of Dementia Cases Typical presentation
Alzheimer's Disease (AD) ~50% Initial short-term memory loss
Vascular Dementia* ~25% Vascular risk factors; neuroimaging evidence of cerebrovascular involvement
Dementia with Lewy Bodies (DLB) 15% Bradykinesia or features of parkinsonism, fluctuating cognition, visual hallucinations
Frontotemporal Dementia (FTD) 3% Younger age, behavioural symptoms, or language impairment
Parkinsons's Disease Dementia (PDD) 0.5%[6] (most cases of Parkinson's will progress to dementia) Dementia occurring > 1 year after onset of Parkinson disease motor symptoms

Rare Dementia Subtypes and Presentation

Subtype Prevalence Typical presentation
Corticobasal Degeneration (CBD) 5 per 100,000 [7] Progressive asymmetric movement disorder with symptoms initially affecting one limb, plus cognitive or behavioural disturbances.
Creutzfeldt-Jakob Disease (CJD) 1 per 1 million Rapid, progressive mental deterioration with myoclonus and abnormal movements. Survival rate is less than 1 year.
Primary Progressive Aphasia (PPA) 2.7 to 15 per 100,000[8] Begins with gradual, subtle language deficits that progresses to a nearly complete inability to speak.
Progressive Supranuclear Palsy (PSP) 5.8 to 6.5 per 100,000[9] Characterized by early postural instability, leading to falls, and a characteristic vertical supranuclear-gaze palsy on physical exam.
Overlap

Dementia is often due to more than one pathology. Some studies have shown that in a general population, 40% of patients have a combination of Alzheimer's Disease (AD) and vascular dementia, while only 30% had pure Alzheimer's and 12% had pure vascular dementia (VaD). About 12% had Alzheimer's combined with Parkinsons's Disease Dementia (PDD) (PD) or Dementia with Lewy Bodies (DLB).[10] </WRAP> </WRAP>

Behavioural and Psychological Symptoms of Dementia (BPSD) will develop in more than 90% of individuals diagnosed with dementia. Symptoms include delusions, hallucinations, aggression, screaming, restlessness, wandering, depression, and anxiety.