Week 11: Later Life Disorders: Ageing, Cognitive Decline, and Alzheimer's Disease

Vocabulary practice flashcards covering age-related cognitive changes, diagnostic classifications of neurocognitive disorders (DSM-5-TR), biological mechanisms of Alzheimer's disease, and assessment and therapeutic approaches.

Healthy Ageing

Expected, gradual, and minor changes in physical and cognitive functioning over time during which neuronal integrity and synaptic plasticity remain largely intact and daily functional independence is preserved.

Cognitive Decline

Persistent and noticeable cognitive deficits driven by pathophysiological processes that exceed normal age-related changes and disrupt safety, social interaction, or routine self-care.

Fluid Intelligence

A domain of cognitive function comprising processing speed, working memory, and pattern recognition that is vital for adaptation and novel problem solving; it peaks in early adulthood and shows a linear decline beginning in the late $20\text{s}$ or early $30\text{s}$.

Crystallised Intelligence

A domain of cognitive function encompassing vocabulary, general knowledge, historical/procedural memory, and expertise important for competence and mastery; it peaks around the $60\text{s}$ or $70\text{s}$, remains stable, and buffers against mild fluid losses.

Neurocognitive Disorders (NCDs)

A group of diagnosable conditions defined by an acquired deficit and decline in cognitive function from a previously attained level of performance across one or more cognitive domains due to underlying brain pathology, injury, or medical disease.

Mild Neurocognitive Disorder

A DSM-5 diagnosis based on evidence of modest cognitive decline from a previous level of performance in one or more cognitive domains that does not interfere with independence in everyday activities, though greater effort or compensatory strategies may be required.

Major Neurocognitive Disorder

A DSM-5 diagnosis characterised by significant cognitive decline from a previous level of performance in one or more cognitive domains that directly interferes with independence in everyday activities.

Complex Attention

A cognitive assessment domain evaluating sustained attention, selective attention, and processing speed; pathological impairment is indicated by an inability to perform mental arithmetic, being easily lost in multistep tasks, and a reduced basic digit span.

Executive Function

A cognitive assessment domain involving planning, decision making, working memory, cognitive flexibility, and error correction; pathological impairment is indicated by an inability to plan daily schedules, manage finances, or execute familiar multi-step processes.

Learning and Memory

A cognitive assessment domain encompassing immediate memory, recent memory, and recall; pathological impairment is indicated by rapid forgetting of recent events and a failure to store new information even when recognition cues are provided.

Social Cognition

A cognitive assessment domain governing recognition of emotions, theory of mind, and behavioural regulation; pathological impairment is indicated by personality changes, behavioural disinhibition, loss of empathy, and apathy.

Alzheimer's Disease

A progressive, irreversible neurodegenerative condition marked by insidious onset and gradual cognitive deterioration across domains without extended plateaus, characterised neuropathologically by accumulations of amyloid-beta ($\text{A}\beta$) plaques and neurofibrillary tangles.

Vascular Dementia

A neurocognitive disorder accounting for approximately $17\%$ of dementia cases, caused by cerebrovascular conditions (such as strokes, transient ischemic attacks, or small vessel disease) that impair blood flow to the brain, commonly presenting with impaired judgement and motor/balance difficulties.

Dementia with Lewy Bodies (DLB)

A progressive neurodegenerative disorder accounting for approximately $4\%$ of dementia cases, caused by abnormal intracellular accumulations of alpha-synuclein proteins (Lewy bodies) and clinically characterised by visual hallucinations, disordered sleep, and early parkinsonism.

Frontotemporal Lobar Degeneration (FTLD)

A group of non-Alzheimer's neurodegenerative disorders causing selective atrophy in the frontal and temporal lobes, most commonly diagnosed between ages $45$ and $60$, presenting with early personality changes and language difficulties while memory and visuospatial abilities are relatively spared.

Delirium

A neurocognitive disturbance featuring an acute onset, fluctuating course, and prominent impairment in attention and awareness triggered by an underlying general medical issue, differentiated from the gradual decline seen in Alzheimer's disease.

APOE Gene (Apolipoprotein E)

A gene providing instructions for a protein that transports cholesterol and fats through the blood and brain; carrying $1$ copy of the $\text{APOE4}$ allele increases Alzheimer's risk by $3\text{--}4\times$, while $2$ copies increase risk by $8\text{--}12\times$.

Amyloid-Beta ($\text{A}\beta$) Plaques

Abnormal extracellular clusters of amyloid protein fragments that reach toxic levels in the brain, triggering a chain reaction that causes dendritic spine death and prevents effective synaptic communication.

Neurofibrillary (Tau) Tangles

Insoluble, twisted strands of hyperphosphorylated tau protein inside neurons that disrupt and collapse axonal nutrient transport pathways, ultimately leading to cellular death.

Histopathology of Alzheimer's Disease

The dual microscopic neuropathological hallmarks of Alzheimer's disease: extracellular amyloid-beta plaques (protein aggregations) and intracellular neurofibrillary tangles (twisted tau protein filaments).

The Cholinergic Hypothesis

The biological model asserting that neurodegeneration of cholinergic neurons along the brain stem and basal forebrain depletes acetylcholine, impairing memory encoding, motivation, attention, and cognitive processing in Alzheimer's disease.

Acetylcholine (ACh)

An excitatory neurotransmitter formed from choline and acetyl coenzyme A by the enzyme choline acetyltransferase (CAT), essential for attention, arousal, and encoding working and spatial memories by modulating hippocampal neurons.

Cholinesterase Inhibitors

A class of pharmacological agents (including Donepezil, Rivastigmine, and Galantamine) that inhibit acetylcholinesterase and butyrylcholinesterase enzymes to increase synaptic acetylcholine availability, temporarily slowing the rate of cognitive loss without halting underlying cell death.

Cognitive Stimulation Therapy (CST)

A structured psychosocial group intervention consisting of $14\text{--}28$ themed activity sessions designed for individuals with mild-to-moderate dementia to improve concentration, language functioning, and memory confidence.

Validation Therapy

A psychological communication approach utilised in the later stages of dementia that respects and validates the emotional reality and experiences of the individual rather than attempting to correct, reorient, or confront their confusion.

Cognitive Reserve

The brain's resilience and capacity to adapt, improvise, and use alternate problem-solving networks to compensate for damage; built through education and intellectual stimulation, it delays the clinical manifestation of cognitive symptoms.