- Last edited on February 23, 2021
Introduction to Dementia
Primer
Dementia is a syndrome characterized by 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). It also includes rapidly progressive dementias that may be fully reversible if the etiology is correctly identified.
Prevalence
The global prevalence of dementia from all causes is estimated to be between 5% and 7% of adults over the age of 60.[1]. Alzheimer’s disease (AD) is the most common cause of dementia worldwide, and dementia rates start at 5-10% at age 70. By age 85, between 25% and 50% of people will exhibit signs of Alzheimer's disease. The percentage of all dementias due to Alzheimer's disease is at least 50% (with some estimates suggesting 60-90%).
Normal Aging and Cognition
Decline in problem-solving, processing speed, and minor delays in word-finding can be common in normal ageing. Retrieval-type memory deficits are also commonly reported. In contrast to dementia, semantic memory and visuospatial functioning is generally preserved.
Prevention
About 35%-40% of dementia cases are attributable to 9 modifiable factors across the lifespan.[2] These factors include:[3]
- Education
- Midlife hypertension
- Midlife obesity
- Hearing loss
- Late-life depression (note: depression likely has a bidirectional relationship with dementia risk, as it can be both a risk factor for dementia and a prodrome of dementia)
- Diabetes
- Physical inactivity
- Social isolation
More recently, the 2020 Lancet Commission on Dementia Prevention, Intervention and Care now include 12 potentially modifiable risk factors across the lifespan that can contribute to dementia:[4]
- Early life (<45 years)
- Less education
- Midlife (age 45 to 65 years)
- Hypertension
- Obesity
- Hearing loss
- Late-life (age >65 years)
- Physical inactivity
- Social isolation
- Diabetes
- Air pollution
There remains debate as to how many cases of dementia with modifiable risk factors can truly be prevented even with risk factor modification.[5]
The World Health Organization (WHO) Dementia Prevention Guidelines
The World Health Organization (WHO) Dementia Prevention Guidelines recommends the following to reduce the risk of dementia:[6]- Physical exercise (there is some conflicting data[7])
- Lose excess weight in midlife
- Adhere to healthy diet (a Mediterranean-style diet may reduce dementia risk)
- Cognitive training can be tried for adults with normal cognition or mild impairment (but the quality of evidence to support this is low)
- Social participation and support are important throughout life (but limited evidence to support)
- Hypertension, diabetes, and depression should be managed according to existing guidelines (but it is not clear whether doing so will specifically lower dementia risk)
Diet
Dietary supplementation to prevent dementia has been a source of controversy due to a lack of convincing evidence from current studies, low quality studies, and multiple confounders in dietary research.[8] Vitamins B and E, polyunsaturated fatty acids, and multivitamins are not recommended for risk reduction of dementia.[9]
Approach to Dementia
When seeing a patient with a non-rapidly progressive dementia (otherwise, see the rapidly progressive dementia approach below), it is good to have a systematic approach. The following is one approach:[10]
- Rule out delirium. Is there an acute onset and fluctuating course + inattention + disorganized thinking? Is there altered level of consciousness?
- Rule out depression (“pseudodementia”). Consider atypical presentations: anxiety, irritability, unexplained physical complaints, worsening cognition. Once the depression is treated, the dementia symptoms go away!
- Rule out any substance use disorders
- Rule out any reversible causes
- Order CBC (anemia), TSH (hypothyroidism), creatinine, electrolytes (hyponatremia), calcium (hypercalcemia), glucose (hyperglycemia), ferritin/iron, and vitamin B12 (vitamin B12 deficiency)
- Creatinine (to assess renal function and ability to clear medications)
- Consider screening for syphillis
- Medication-induced “dementia”
- Is there polypharmacy that could be contributing to the cognitive impairment?
- Is there the use of any anticholinergic medications (and anticholinergic toxicity?)
- Is there the use of other medications that could cause cognitive issues?
- e.g. - steroid dementia syndrome related to glucocorticoid use.
- Is it dementia, mild cognitive impairment (MCI), or normal aging?
- Major neurocognitive disorder (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
Rapidly Progressive Dementias
Rapidly Progressive Dementias (RPDs) are dementias that progress quickly – over the course of weeks to months (in rarer cases, may be over a period of 1-2 years).[12] Treatment of an RPD is dependent on the etiology of the dementia, some of which are fully treatable. This makes early recognition critical. Broadly, RPDs can be broken down into different etiologies:
- Prion disease (e.g. - Creutzfeldt-Jakob Disease (CJD))
- Neurodegenerative diseases (e.g. - early onset Alzheimer's Disease (AD))
- Autoimmune
- Infectious
- Psychiatric
- Neoplastic
- Toxic-Metabolic
- Vascular
- Leukoencephalopathies (e.g. - Multiple Sclerosis (MS), Progressive Multifocal Leukoencephalopathy)
Mnemonic
Evaluating for RPDs requires a detailed and systematic approach, and a mnemonic can be useful to do this. The mnemonicVITAMINS
can be used to remember the V
- VascularI
- InfectiousT
- Toxic-MetabolicA
- AutoimmuneM
- Metastasis/NeoplasticI
- IatrogenicN
- NeurodegenerativeS
- Systemic/Seizures
Common Dementias
The most common dementia subtypes are below:
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%[13] (most cases of Parkinson's will progress to dementia) | Dementia occurring > 1 year after onset of Parkinson disease motor symptoms |
Rare Dementias
Rarer dementia subtypes include the following:
Rare Dementia Subtypes and Presentation
Subtype | Prevalence | Typical presentation |
---|---|---|
Corticobasal Degeneration (CBD) | 5 per 100,000 [14] | 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[15] | 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[16] | Characterized by early postural instability, leading to falls, and a characteristic vertical supranuclear-gaze palsy on physical exam. |
Mixed Presentations
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).[17]
Behavioural and Psychological Symptoms of Dementia
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.
Dementia, Depression, or Delirium?
- In the geriatric population, it is important to differentiate between delirium, dementia, and depression, which can be difficult to distinguish.[18][19][20] The prevalence of delirium superimposed on dementia ranges anywhere from 22% to 89% of hospitalized and community populations aged 65 and older with dementia.
- The negative outcomes of these co-occurring conditions include accelerated and long-term cognitive, functional decline, institutionalization, re-hospitalization, and increased mortality.[21]
A Comparison of Delirium, Dementia, and Depression
Adapted from: Fong, T., et al. Delirium in elderly adults: diagnosis, prevention and treatment. Nature Reviews Neurology 5.4 (2009): 210.Delirium | Dementia | Depression | |
---|---|---|---|
Cardinal feature | Confusion and Inattention | Memory loss | Sadness, anhedonia |
Onset | Acute or subacute | Insidious | Slow |
Course | Fluctuating, often worse at night | Chronic, progressive (but stable over the course of a day) | Single or recurrent episodes; can be chronic |
Duration | Hours to months | Months to years | Weeks to years |
Level of Conciousness (LOC) | Impaired, fluctuates | Normal in early stages | Normal |
Attention (i.e. - able to focus on tasks) | Poor | Normal (except in late stages) | May be impaired |
Orientation (i.e. - date, location) | Fluctuates | Poor | Normal |
Memory (i.e. - short-term memory) | Poor | Poor | May be impaired |
Hallucinations | Common (visual) | Rare, except in late stages (and depends on type of dementia) | Not usually (only if psychotic depression) |
Delusions | Fleeting, non-systematized | Often absent | Not usually (only if psychotic depression) |
Psychomotor | Increased (hyperactive) or reduced (hypoactive) | No | Yes |
Reversibility | Yes | Rarely | Yes |
EEG Findings | Moderate to severe background slowing | Normal or mild diffuse slowing | Normal (usually) |
Neuroimaging
For older patients with cognitive symptoms, neuroimaging with CT is recommended if the following criteria is present:[22]
- Age less than 60 years
- Rapid (e.g., 1 or 2 months) unexplained decline in cognition or function
- “Short” duration of dementia (less than 2 years)
- Recent and signicant head trauma
- Unexplained neurological symptoms (e.g. new onset of severe headache or seizures)
- History of cancer (especially in sites and types that metastasize to the brain)
- Use of anticoagulants (i.e. - history of atrial fibrillation) or history of bleeding disorder
- History of urinary incontinence and gait disorder early in the course of dementia (as may be found in normal pressure hydrocephalus)
- Any new localizing sign (e.g., hemiparesis or a Babinski reflex)
- Unusual or atypical cognitive symptoms or presentation (e.g. progressive aphasia)
- Gait disturbance
Guidelines
Dementia Guidelines
Guideline | Location | Year | Website | |
---|---|---|---|---|
Canadian Consensus Conference on the Diagnosis and Treatment of Dementia (CCCDTD) - Diagnosis and Treatment | Canada | 2020 | - | Link |
CCCDTD - Pharmacological Recommendations for Symptomatic Treatment of Dementia | Canada | 2012 | - | Link |
National Institute for Health and Care Excellence (NICE) | UK | 2018 | - | Link |
American Psychiatric Association (APA) | USA | 2007, 2014 | - | • Guideline (2007) • Guideline Watch (2014) • Quick Reference |