Dementia: Definition and Types

Study Notes

Dementia is a syndrome caused by brain disease, usually chronic or progressive.
It affects multiple higher cortical functions: memory, thinking, orientation, comprehension, calculation, learning, language, and judgment.
Consciousness remains unaffected.
Cognitive impairment is often accompanied by deterioration in emotional control, social behavior, or motivation (WHO 1992, ICD-10).
Many subtypes exist (70+, 100+, 200+ reported in different studies).
Different types of memory are impacted: perceptual representation, working memory, semantic memory, episodic memory, and procedural memory.
The "Big Four" dementia types are: Alzheimer's Disease (AD), Vascular Dementia (VaD), Dementia with Lewy Bodies (DLB), and Frontotemporal Dementia (FTD).
Diagnostic criteria vary depending on the type of dementia, with preferred criteria differing from those used in ICD and DSM systems.

Prevalence rates increase significantly with age.
Rates are: 1 in 1000 (40-65 years), 1 in 50 (65-70 years), 1 in 20 (70-80 years), and 1 in 5 (80+ years).
A 2022 study showed a national diagnostic rate of 62% versus a benchmark rate of 66.7%.
Dementia UK (2007) reported the following percentages for dementia types: DAT (62%), VaD (17%), DLB (4%), FTD (10-15%), and others (2-5%).

Characterized by dementia, gradual progression, intact consciousness, onset after age 40, and absence of other causes (NINCDS/ADRDA criteria).
Cognitive decline progresses over time.

Involves dementia, cerebrovascular disease, focal stroke signs, impairment of memory and at least one other cognitive domain, and evidence of relevant cerebrovascular disease (NINDS-AIREN criteria).
Onset often within three months of a stroke, or may present with abrupt deterioration or fluctuating, stepwise progression.

Features progressive cognitive decline impacting daily functioning.
Requires two of the following: fluctuating cognition, recurrent visual hallucinations, spontaneous Parkinsonism motor features.
Supportive features include: falls, syncope, neuroleptic sensitivity, paranoid delusions, and hallucinations in other modalities (McKeith et al., 1996).

Characterized by insidious onset, gradual progression, early decline in social conduct, impairment in self-regulation, emotional blunting, and early loss of insight (Lund-Manchester criteria).

Progression stages include mild, moderate, and severe, with a typical lifespan of 4-8 years (though it can be up to 20).
Death often results from pneumonia or other comorbidities.

Causes include biological factors (chromosomes, altered brain pathology), psychosocial factors (malignant social psychology), and environmental factors (lifestyle, physical environment).
Kitwood's (1997) model emphasizes psychological needs: comfort, occupation, attachment, identity, and inclusion.
"Malignant social psychology" describes harmful behaviors and attitudes that negatively impact people with dementia.