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]

When being asked to see a patient with dementia, it is good to have a systematic approach. The following is one approach to diagnosing dementia.[6]

  1. Rule out delirium. Is there an acute onset and fluctuating course + inattention + disorganized thinking? Is there altered level of consciousness?
    • Urinary Tract Infections (UTIs) are especially common in the elderly and frequent culprits of delirium! Don't forget that a negative urine culture does not always mean there is no UTI, especially if the patient is symptomatic.[7]
  2. Rule out depression (“pseudodementia”). Consider atypical presentations: anxiety, irritability, unexplained physical complaints, worsening cognition. Once the depression is treated, the dementia symptoms go away!
  3. Rule out any substance use disorders
  4. Rule out any reversible causes
    • Order CBC (anemia), TSH (hypothyroidism), creatinine, electrolytes (hyponatremia), calcium (hypercalcemia), glucose (hyperglycemia), and vitamin B12 (vitamin B12 deficiency)
    • Creatinine (to assess renal function and ability to clear medications)
    • Consider neuroimaging such as CT or MRI
    • Consider rapid plasma reagin (RPR), LFTs
    • Is there the use of any anticholinergic medications (and anticholinergic toxicity?)
  5. Is it dementia, mild cognitive impairment (MCI), or normal aging?
    • Dementia: objective findings of cognitive loss with impairment of ADLs
    • Mild Cognitive Impairment: objective findings of cognitive loss without impairment of ADLs
    • Normal cognitive aging: no objective findings of cognitive loss

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
Lewy Body Dementia (LBD) 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%[8] (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 [9] 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[10] 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[11] Characterized by early postural instability, leading to falls, and a characteristic vertical supranuclear-gaze palsy on physical exam.

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 Lewy Body Dementia (LBD).[12] </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.