Alzheimer's Disease

1. Clinical Overview

Summary

Alzheimer's disease (AD) is the most common cause of dementia worldwide, accounting for 60-80% of all dementia cases.[1] It is a progressive neurodegenerative disorder characterised pathologically by the extracellular accumulation of amyloid-beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein.[2] The disease follows a characteristic clinical trajectory beginning with impairment of episodic memory—the ability to encode, store, and retrieve new information about personal experiences—before progressing to affect language, visuospatial abilities, executive function, and ultimately all cognitive domains.[3]

The neuropathological changes in AD begin 15-20 years before clinical symptoms manifest, during a preclinical phase when biomarkers may be positive but cognition remains normal.[4] This extended preclinical window has become the focus of disease-modifying therapeutic development. The amyloid cascade hypothesis, which posits that Aβ accumulation initiates a pathological cascade leading to tau pathology, neurodegeneration, and dementia, has driven drug development for decades and recently yielded the first approved disease-modifying therapies.[5]

While there remains no cure for Alzheimer's disease, symptomatic treatments including acetylcholinesterase inhibitors and memantine provide modest cognitive and functional benefits.[6] The recent approval of anti-amyloid monoclonal antibodies (lecanemab, aducanumab) represents a paradigm shift toward disease modification, though clinical benefits remain modest and significant risks exist.[7] Early diagnosis enables timely intervention, advance care planning, access to support services, and participation in clinical trials. The global burden of AD is immense, with profound impacts on patients, families, healthcare systems, and economies worldwide.

Key Facts

Clinical Pearls

"Episodic Memory First": Alzheimer's disease classically presents with impairment of recent episodic memory before other cognitive domains. The patient cannot recall new information despite normal immediate recall. If personality change, executive dysfunction, or language impairment precedes memory loss, strongly consider frontotemporal dementia variants.

The Amyloid-Tau-Neurodegeneration (ATN) Framework: Modern AD diagnosis uses biomarkers classified as A (amyloid), T (tau), and N (neurodegeneration). An A+T+N+ profile indicates Alzheimer's disease across the clinical spectrum, from preclinical to dementia stages.[4]

APOE ε4 — Risk Factor, Not Deterministic: The APOE ε4 allele is the strongest genetic risk factor for sporadic late-onset AD. Heterozygotes have 3-4× increased risk; homozygotes have 10-15× increased risk compared to ε3/ε3 carriers. However, many ε4 carriers never develop AD, and many AD patients lack ε4. Do NOT use APOE genotyping alone for diagnosis.[10]

The Cholinergic Hypothesis: Loss of cholinergic neurons in the nucleus basalis of Meynert leads to cortical acetylcholine depletion, correlating with cognitive symptoms. This remains the basis for AChE inhibitor therapy, though it addresses symptoms rather than underlying pathology.[11]

Treatable Mimics: Always exclude potentially reversible causes of cognitive impairment before diagnosing AD: vitamin B12 deficiency, hypothyroidism, normal pressure hydrocephalus, subdural haematoma, depression (pseudodementia), and medication effects.

Why This Matters Clinically

Alzheimer's disease represents one of the greatest healthcare challenges of the 21st century. By 2050, the global prevalence is projected to triple to over 150 million people, with the majority in low- and middle-income countries.[1] The economic costs are staggering—estimated at over $1 trillion globally in 2019—and the burden on informal caregivers is immense, contributing to significant carer morbidity and mortality.[12]

Accurate early diagnosis distinguishes AD from potentially treatable causes of cognitive decline and enables:

• Timely initiation of symptomatic treatment
• Access to emerging disease-modifying therapies where appropriate
• Advance care planning while capacity remains
• Legal arrangements (Lasting Power of Attorney, will preparation)
• Access to support services for patients and families
• Participation in clinical trials
• Planning for future care needs

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2. Epidemiology

Incidence and Prevalence

Alzheimer's disease is the most common neurodegenerative disorder and the leading cause of dementia worldwide. The epidemiology is characterised by exponential increases with advancing age.[8]

The incidence of AD approximately doubles every 5 years after age 65. However, age-standardised incidence may be declining in high-income countries, possibly due to improvements in cardiovascular health, education, and overall living conditions.[14]

Demographics

Risk Factors

The Lancet Commission on Dementia Prevention (2020, updated 2024) identified 12 potentially modifiable risk factors that together account for approximately 40% of dementia cases worldwide.[15] Addressing these represents the most impactful current strategy for reducing dementia burden.

Non-Modifiable Risk Factors

Modifiable Risk Factors (Lancet Commission 2020/2024)

Clinical Implication: These modifiable risk factors provide actionable targets for primary prevention. Even small risk reductions across populations could substantially reduce dementia incidence globally.[15]

Protective Factors

Evidence supports several factors associated with reduced AD risk:

• Higher educational attainment: Cognitive reserve allows compensation for pathology
• Regular physical activity: 150+ minutes moderate aerobic exercise weekly associated with 30-40% risk reduction
• Mediterranean diet: High in vegetables, fruits, whole grains, fish, olive oil; associated with lower risk
• Cognitive engagement: Lifelong learning, mentally stimulating activities
• Social engagement: Strong social networks, regular social activity
• Cardiovascular health: Optimal management of BP, cholesterol, diabetes
• Moderate alcohol consumption: J-shaped relationship (though causality debated)

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3. Pathophysiology

The Amyloid Cascade Hypothesis

The amyloid cascade hypothesis, proposed by Hardy and Higgins in 1992, remains the dominant framework for understanding AD pathogenesis.[16] This hypothesis posits that aberrant processing and accumulation of amyloid-beta (Aβ) peptide is the initiating event that triggers a cascade of downstream pathological processes culminating in neurodegeneration and dementia.

Step 1: Amyloid-Beta Generation and Accumulation

Amyloid precursor protein (APP) is a transmembrane protein normally processed by two pathways:

Non-amyloidogenic pathway (normal):

• α-secretase cleaves APP within the Aβ domain
• Produces soluble APPα (neuroprotective) + C83 fragment
• Precludes Aβ formation

Amyloidogenic pathway (pathological):

• β-secretase (BACE1) cleaves APP at N-terminus of Aβ domain → sAPPβ + C99
• γ-secretase complex (including presenilin 1/2) cleaves C99 → Aβ peptides
• Produces Aβ40 (90%) and Aβ42 (10%)
• Aβ42 is more hydrophobic and aggregation-prone

Aggregation cascade:

1. Aβ monomers → oligomers (most neurotoxic species)
2. Oligomers → protofibrils → fibrils
3. Fibrils → mature amyloid plaques (diffuse → neuritic)

The imbalance between Aβ production and clearance leads to progressive accumulation. Clearance mechanisms include:

• Enzymatic degradation (neprilysin, insulin-degrading enzyme)
• Receptor-mediated clearance (LRP1, RAGE)
• Glymphatic clearance (sleep-dependent)
• Vascular clearance

Step 2: Tau Pathology and Neurofibrillary Tangles

Tau is a microtubule-associated protein essential for axonal transport. In AD:

1. Hyperphosphorylation: Kinase/phosphatase imbalance leads to abnormal tau phosphorylation
2. Microtubule dissociation: Hyperphosphorylated tau detaches from microtubules
3. Aggregation: Free tau forms paired helical filaments (PHFs)
4. NFT formation: PHFs accumulate as intracellular neurofibrillary tangles
5. Cell death: Neurons containing NFTs eventually die, releasing "ghost tangles"

Braak staging describes stereotypical tau pathology progression:[17]

• Stages I-II: Transentorhinal (presymptomatic)
• Stages III-IV: Limbic (prodromal/MCI)
• Stages V-VI: Neocortical (dementia)

Key concept: While amyloid deposition drives the process, tau pathology correlates more closely with clinical symptoms and neurodegeneration. This dissociation has important therapeutic implications.

Step 3: Neuroinflammation

Microglial activation and astrocyte reactivity occur early in AD:

• Microglia: Initially clear Aβ via phagocytosis; become chronically activated and dysfunctional
• Astrocytes: Become reactive, contribute to inflammation, impaired glutamate handling
• Cytokine release: IL-1β, IL-6, TNF-α create neurotoxic environment
• Complement activation: Classical pathway activation around plaques
• TREM2: Genetic variants affecting microglial function increase AD risk

Step 4: Synaptic Dysfunction and Neurodegeneration

Progressive synaptic loss correlates best with cognitive decline:

1. Aβ oligomers impair synaptic plasticity (LTP inhibition)
2. Tau pathology disrupts axonal transport
3. Mitochondrial dysfunction and oxidative stress
4. Calcium dysregulation
5. Synaptic loss → neuronal loss → brain atrophy

Regional vulnerability: The hippocampus and entorhinal cortex are affected earliest, explaining the primacy of episodic memory impairment.

Step 5: Cholinergic Deficit

Loss of cholinergic neurons in the nucleus basalis of Meynert (nbM) leads to:

• Reduced cortical and hippocampal acetylcholine
• Correlation with cognitive symptoms
• Basis for cholinesterase inhibitor therapy

The cholinergic hypothesis, while incomplete, explains the symptomatic benefit of AChE inhibitors.[11]

Genetic Basis

Early-Onset Familial AD (EOFAD) — less than 5% of cases

These are autosomal dominant with high penetrance (typically > 90%). PSEN1 mutations are most common (70% of EOFAD), with onset typically 30-60 years.

Late-Onset AD (LOAD) — > 95% of cases

APOE ε4 is the strongest genetic risk factor. The APOE gene has three alleles (ε2, ε3, ε4):[10]

Genome-wide association studies (GWAS) have identified > 75 additional risk loci, including genes involved in:[18]

• Immune function (TREM2, CD33, MS4A, CR1)
• Lipid metabolism (CLU, ABCA7)
• Endocytosis (BIN1, PICALM)
• Tau biology (MAPT region)

Classification

Atypical Variants of Alzheimer's Disease

While typical AD presents with predominant amnesia, several atypical clinical syndromes are recognised:

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4. Clinical Presentation

Stages of Alzheimer's Disease

The NIA-AA framework defines AD as a biological entity (defined by biomarkers) with a clinical spectrum from preclinical to dementia:[4]

Symptoms by Stage

Mild Cognitive Impairment / Early AD

Memory (hallmark symptom):

• Forgetting recent events and conversations
• Repeating questions or stories within minutes
• Misplacing objects in unusual places
• Difficulty learning new information
• Relying more on memory aids, calendars, notes

Language:

• Word-finding difficulties (anomia)
• Pauses in conversation
• Circumlocution (talking around forgotten words)
• Reduced vocabulary

Executive function:

• Difficulty with complex tasks (finances, medications)
• Poor planning and organisation
• Trouble with multi-step tasks
• Reduced mental flexibility

Visuospatial:

• Getting lost in familiar places
• Difficulty with navigation
• Problems with spatial judgment (parking)

Behavioural/psychological:

• Subtle personality changes
• Apathy, reduced initiative
• Mild depression or anxiety
• Social withdrawal
• Reduced insight (anosognosia)

Moderate AD

Cognitive:

• Marked memory impairment (remote memory now affected)
• Difficulty recognising family and friends
• Disorientation to time and place
• Language deterioration (comprehension, fluency)
• Unable to handle finances or medications

Functional:

• Needs help with IADLs (cooking, shopping, transport)
• Emerging dependence in personal care
• May become lost if unsupervised
• Safety concerns at home

Behavioural/psychological (BPSD):

• Agitation and irritability (40-60%)
• Wandering behaviour
• Sleep disturbance (day-night reversal)
• Delusions (commonly paranoid: theft, infidelity)
• Hallucinations (less common than in DLB)
• Aggression (verbal or physical)
• Resistance to care
• Sundowning (evening confusion)

Severe AD

Cognitive:

• Profound memory loss (cannot recognise family)
• Loss of meaningful speech (echolalia, mutism)
• Loss of comprehension
• Complete disorientation

Functional:

• Total dependence for all ADLs
• Incontinence (urinary, then faecal)
• Dysphagia (aspiration risk)
• Mobility loss (wheelchair/bed-bound)
• Contractures

Physical:

• Weight loss and cachexia
• Recurrent infections
• Seizures (10-20%)
• Myoclonus
• Primitive reflexes present (grasp, suck)

Signs on Examination

Early Disease

• Often normal general and neurological examination
• Cognitive testing abnormalities (see below)
• Subtle word-finding pauses
• Difficulty with complex commands

Moderate Disease

• Disorientation during interview
• Poor recall of recent events discussed
• Language errors (paraphasia, circumlocution)
• Apraxia (difficulty with learned movements)
• Reduced insight

Late Disease

• Frontal release signs: grasp reflex, palmomental reflex, glabellar tap (Myerson's sign), snout reflex
• Paratonia (gegenhalten) — limb resistance to passive movement
• Rigidity and bradykinesia
• Gait disturbance
• Myoclonus
• Seizures
• Cachexia

Red Flags — When to Reconsider the Diagnosis

[!CAUTION] Red Flags Suggesting Alternative Diagnosis:

• Rapid progression (less than 6 months to severe impairment) → CJD, autoimmune encephalitis, paraneoplastic, malignancy
• Young onset (less than 65 years) with atypical features → genetic AD, FTD, Huntington's, metabolic disorders
• Prominent early motor signs → DLB, PSP, CBD, vascular dementia, Parkinson's dementia
• Personality change before memory → Frontotemporal dementia (behavioural variant)
• Early prominent visual hallucinations → Dementia with Lewy Bodies
• Gait + incontinence + dementia triad → Normal Pressure Hydrocephalus (potentially reversible!)
• Stepwise deterioration → Vascular dementia
• Focal neurological signs → Stroke, space-occupying lesion, subdural haematoma
• Fluctuating consciousness → DLB, delirium
• Seizures early in course → Autoimmune encephalitis, tumour, EOFAD

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5. Clinical Examination

Structured Cognitive Assessment

Bedside Cognitive Screening Tools

Cognitive Domains to Assess

The Clock Drawing Test

A sensitive screening test assessing multiple cognitive domains:

• Visuospatial ability
• Executive function (planning, organisation)
• Semantic memory
• Constructional praxis

Scoring (multiple methods exist):

• Numbers present and correctly placed
• Two hands present
• Correct time shown
• Overall gestalt

Common errors in AD:

• Missing numbers
• Numbers outside circle
• Numbers clustered on one side
• Single hand or incorrect hand lengths
• Perseveration

General Examination

• Nutritional status: Cachexia (late disease)
• Self-care: Grooming, hygiene, dress
• Affect: Depression, apathy, anxiety
• Gait: Normal early; impaired late
• Signs of falls: Bruising, injuries

Neurological Examination

Cranial nerves: Usually normal (helps exclude focal lesions)

Motor examination:

• Tone: Paratonia late; rigidity (consider DLB)
• Power: Preserved until late
• Reflexes: Brisk in moderate-severe disease
• Plantar response: Normal or extensor late

Primitive reflexes (frontal release signs in moderate-severe AD):

• Grasp reflex
• Palmomental reflex
• Glabellar tap (Myerson's sign — cannot suppress blink)
• Snout reflex
• Rooting reflex

Sensory: Normal (abnormalities suggest alternative diagnosis)

Functional Assessment

Essential for diagnosis and staging:

Instrumental Activities of Daily Living (IADLs):

• Managing finances
• Taking medications correctly
• Cooking and meal preparation
• Shopping
• Using telephone
• Housework
• Using transportation
• Managing correspondence

Basic Activities of Daily Living (ADLs):

• Bathing
• Dressing
• Grooming
• Toileting
• Continence
• Feeding
• Transfers/mobility

Validated Scales:

• Bristol Activities of Daily Living Scale
• Barthel Index
• Disability Assessment for Dementia (DAD)
• Functional Activities Questionnaire (FAQ)

Informant History

Essential component — patients often lack insight:

• Obtain from spouse, family member, carer
• Corroborate patient's account
• Clarify timeline and progression
• Assess baseline function
• Document behavioural changes
• Evaluate carer burden

Useful informant questionnaires:

• Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)
• AD8 Dementia Screening Interview
• GPCOG Informant Section

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6. Investigations

Aims of Investigation

1. Confirm cognitive impairment objectively
2. Characterise the pattern of deficits
3. Exclude potentially reversible causes
4. Support positive diagnosis of AD
5. Stage disease severity
6. Establish baseline for monitoring

First-Line Investigations

Cognitive Testing

• Formal cognitive assessment (MMSE, MoCA, or ACE-III)
• Comparison to estimated premorbid ability

Blood Tests — Excluding Reversible Causes

Consider based on clinical picture:

• Syphilis serology (if risk factors)
• HIV serology (if risk factors)
• Copper, caeruloplasmin (if young onset — Wilson's disease)
• Autoimmune screen (ANA, anti-TPO) if autoimmune suspected
• Vasculitis screen

Neuroimaging

Structural Imaging (All Patients)

MRI Brain (Preferred):

CT Head (if MRI contraindicated):

• Less sensitive than MRI
• Can show medial temporal atrophy
• Excludes structural lesions, NPH, subdural haematoma
• Reasonable for initial assessment in elderly

Functional/Molecular Imaging (Specialist)

Clinical Caveat: Amyloid PET positivity increases with age in cognitively normal individuals (~30% of those 70+), so a positive scan does not diagnose AD dementia — clinical correlation is essential.

CSF Biomarkers

CSF analysis provides direct evidence of AD pathology in the brain:[19]

CSF Profile in AD: ↓Aβ42 + ↑t-tau + ↑p-tau

Indications for CSF analysis:

• Young-onset dementia (less than 65)
• Atypical presentations
• Diagnostic uncertainty
• Rapid progression (to exclude CJD)
• Clinical trial eligibility
• Differentiating AD from FTD

Emerging Blood Biomarkers

Significant advances in blood-based biomarkers are transforming AD diagnosis:[20]

Genetic Testing

Indications:

• Early-onset AD (less than 65 years), especially with family history
• Autosomal dominant family history
• Consideration of disease-modifying therapy (APOE genotyping for safety)

Testing options:

• APOE genotyping (risk factor only — not diagnostic)
• APP, PSEN1, PSEN2 sequencing (if EOFAD suspected)
• Genetic counselling mandatory before and after testing

Diagnostic Criteria

NIA-AA Research Framework (2018) — ATN Classification[4]

Defines AD biologically based on biomarkers:

A = Amyloid (CSF Aβ42 or amyloid PET) T = Tau (CSF p-tau or tau PET) N = Neurodegeneration (CSF t-tau, FDG-PET, MRI atrophy)

NIA-AA Clinical Criteria (2011)[21]

Probable AD Dementia (core clinical criteria):

1. Dementia established by clinical and cognitive testing
2. Insidious onset (months to years)
3. Clear-cut history of worsening cognition
4. Initial prominent deficits in ONE of:
   • Amnestic presentation (most common)
   • Non-amnestic: Language, visuospatial, or executive
5. No evidence of other causes (cerebrovascular, DLB, FTD, other)

Possible AD Dementia:

• Atypical course (sudden onset, insufficient decline history)
• OR evidence of other contributing pathology

Probable AD with increased certainty:

• Documented progressive decline
• Positive biomarkers (genetic mutation or ATN biomarkers)

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7. Management

Principles of Management

1. Diagnose early — enables intervention, planning, support
2. Treat cognitive symptoms — AChE inhibitors, memantine
3. Consider disease-modification — anti-amyloid therapies in appropriate patients
4. Manage BPSD — non-pharmacological first; judicious pharmacology
5. Support function — occupational therapy, environmental modification
6. Support carers — education, respite, services
7. Plan ahead — advance care planning, legal arrangements
8. Optimise comorbidities — cardiovascular risk factors, depression

Non-Pharmacological Interventions

Evidence supports multiple non-drug approaches as first-line for many symptoms:[22]

NICE Recommendation: Cognitive stimulation therapy should be offered to all people with mild-to-moderate dementia.[22]

Pharmacological Management — Symptomatic Treatment

Acetylcholinesterase Inhibitors (AChEIs)

First-line for mild-to-moderate AD (MMSE 10-26). Mechanism: Inhibit acetylcholinesterase, increasing synaptic acetylcholine.[6]

Side Effects:

• Gastrointestinal: Nausea, vomiting, diarrhoea, anorexia (5-20%)
• Cardiovascular: Bradycardia, heart block, syncope (check ECG if cardiac history)
• CNS: Vivid dreams, insomnia, fatigue
• Urinary: Incontinence
• Other: Muscle cramps, weight loss

Contraindications:

• Sick sinus syndrome
• Significant conduction defects (unless pacemaker)
• Active peptic ulcer disease
• Severe hepatic impairment (rivastigmine)

Monitoring:

• Baseline ECG if cardiac history
• Review at 3 months for response and tolerability
• Continue if stable/improving on cognition and function
• MMSE typically improves by 1-3 points or stabilises

Memantine

NMDA receptor antagonist for moderate-to-severe AD (MMSE less than 20). Mechanism: Blocks excessive glutamate activity at NMDA receptors, preventing excitotoxicity.[6]

Indications:

• Moderate-to-severe AD (MMSE less than 20) as monotherapy or add-on
• When AChEI not tolerated or contraindicated
• NICE recommends for moderate-severe AD only

Side Effects:

• Dizziness, headache
• Constipation
• Somnolence
• Hypertension (rare)
• Generally well tolerated

DOMINO Trial (2012): Demonstrated benefit of continuing donepezil into moderate-severe disease and additional benefit of memantine combination.[23]

Pharmacological Management — Disease-Modifying Therapies

Anti-Amyloid Monoclonal Antibodies

The recent approval of amyloid-targeting therapies represents the first disease-modifying treatments for AD:[7]

CLARITY-AD Trial (2023):[7]

• 1,795 patients with early AD (MCI or mild dementia with amyloid positivity)
• Lecanemab IV every 2 weeks vs placebo for 18 months
• Primary endpoint: CDR-SB decline reduced by 0.45 points (27% less decline)
• Amyloid PET: Significant reduction in amyloid burden
• ARIA: Amyloid-Related Imaging Abnormalities
  • "ARIA-E (oedema): 12.6% (2.8% symptomatic)"
  • "ARIA-H (haemorrhage): 17%"
  • Higher risk in APOE ε4 homozygotes

Eligibility Considerations:

• Early AD (MCI or mild dementia)
• Amyloid positivity confirmed (PET or CSF)
• APOE genotyping (higher ARIA risk in ε4/ε4)
• MRI surveillance required (baseline, during infusions)
• Exclude significant cerebral amyloid angiopathy
• Anticoagulation considerations

Limitations:

• Modest clinical benefit (statistical vs clinical significance debated)
• High cost (~$26,500/year in US)
• Infusion requirements (every 2 weeks)
• ARIA risks requiring MRI monitoring
• Limited to early-stage disease

Management of Behavioural and Psychological Symptoms of Dementia (BPSD)

Up to 90% of dementia patients experience BPSD. Non-pharmacological approaches are first-line.[22]

Non-Pharmacological Approaches (First-Line)

1. Identify and treat underlying causes:

   • Pain (UTI, constipation, dental problems)
   • Delirium (infection, medication, dehydration)
   • Sensory impairment (vision, hearing)
   • Environmental factors (noise, over-stimulation)

2. Environmental modifications:

   • Consistent routine
   • Appropriate lighting
   • Reduce clutter and noise
   • Orientation cues
   • Safe wandering areas

3. Behavioural strategies:

   • Person-centred care approach
   • Validation therapy
   • Distraction and redirection
   • Music and art therapy
   • Animal-assisted therapy

Pharmacological Management (When Non-Pharmacological Fails)

[!WARNING] Antipsychotic Warning: Antipsychotics increase mortality risk in dementia patients (1.5-1.7× relative risk). MHRA advises:

• Use only for severe symptoms unresponsive to other measures
• Use lowest effective dose for shortest time
• Review at least every 6 weeks
• Risperidone is the only antipsychotic licensed for short-term treatment of persistent aggression in moderate-severe AD

Supportive Care and Planning

Care Settings and Disposition

• Community (majority): Memory clinic follow-up, GP shared care, community mental health team support
• Specialist input: Old age psychiatry, neurology (atypical cases), geriatric medicine
• Care home: When home care is no longer safe or feasible; often needed by moderate-severe stage
• Hospital: Only for acute medical illness; high delirium risk; avoid prolonged admission

End-of-Life Care

In advanced dementia, focus shifts to comfort and palliation:

• Prioritise comfort over life prolongation
• Manage pain (often under-recognised in dementia)
• Oral care and hydration
• Decisions about feeding (PEG feeding not recommended in advanced dementia)
• Treatment of infections (consider individual benefit vs burden)
• Spiritual and psychological support
• Family support and bereavement care

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8. Complications

Early Disease Complications

Moderate Disease Complications

Late Disease Complications

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9. Prognosis and Outcomes

Natural History

Alzheimer's disease is progressive and currently incurable. The typical disease trajectory involves gradual decline over 8-12 years from symptom onset, though individual variation is substantial.[9]

Survival

Causes of Death

1. Pneumonia/respiratory infection (most common — often aspiration)
2. Cardiovascular disease
3. Cerebrovascular disease
4. Inanition/cachexia
5. Falls and fall-related injuries

Prognostic Factors

Associated with Faster Decline / Shorter Survival

• Older age at diagnosis
• Severe cognitive impairment at diagnosis (lower MMSE)
• Rapid decline in first year
• Early language impairment
• Behavioural symptoms (BPSD)
• Extrapyramidal signs
• Early functional impairment
• Medical comorbidities (especially cardiovascular, diabetes)
• Male sex (in some studies)
• Psychotic features
• Malnutrition

Associated with Slower Decline / Longer Survival

• Younger age at symptom onset
• Higher education / cognitive reserve
• Milder cognitive impairment at diagnosis
• Female sex
• Good nutrition
• Active social support
• Preserved insight (early)
• Absence of BPSD
• Fewer medical comorbidities
• Engagement in cognitive/physical activities

Treatment Outcomes

Institutionalisation

• Approximately 50% of patients with moderate-severe AD require care home placement
• Median time from diagnosis to care home: 3-5 years
• Predictors of earlier placement: BPSD, caregiver burden, living alone, faster decline

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10. Guidelines and Evidence

Key Guidelines

Landmark Trials

DOMINO Trial (2012)[23]

• Population: 295 patients with moderate-severe AD
• Intervention: Continue vs discontinue donepezil ± add memantine
• Key Finding: Continuing donepezil was associated with better cognition and function than stopping; memantine combination showed additional benefit
• Clinical Impact: Continue AChEIs into moderate-severe disease; combination therapy beneficial

CLARITY-AD (2023)[7]

• Population: 1,795 patients with early AD (MCI/mild dementia, amyloid-positive)
• Intervention: Lecanemab vs placebo every 2 weeks for 18 months
• Key Finding: 27% slowing of clinical decline (CDR-SB); significant amyloid reduction
• Clinical Impact: First disease-modifying treatment with clear efficacy; FDA full approval; high cost and safety concerns limit use

FINGER Trial (2015)[24]

• Population: 1,260 at-risk elderly with risk factors
• Intervention: Multi-domain lifestyle intervention (diet, exercise, cognitive training, vascular risk management)
• Key Finding: Improved cognitive function vs control group
• Clinical Impact: Supports multi-domain prevention strategies

AD2000 Trial (2004)

• Population: 565 patients with AD
• Intervention: Donepezil vs placebo (pragmatic design)
• Key Finding: Modest cognitive benefit; no significant delay to institutionalisation
• Clinical Impact: Tempered expectations; benefit is symptomatic, not disease-modifying

Evidence Levels Summary

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11. Exam-Focused Content

Common Exam Questions

1. "Describe the pathophysiology of Alzheimer's disease."
2. "What are the risk factors for Alzheimer's disease and which are modifiable?"
3. "How would you investigate a 72-year-old with progressive memory impairment?"
4. "What is the role of CSF biomarkers and amyloid PET in diagnosing AD?"
5. "Compare and contrast Alzheimer's disease with other dementias."
6. "Discuss the pharmacological management of Alzheimer's disease."
7. "What are the emerging disease-modifying therapies for AD?"
8. "How would you manage behavioural symptoms in a patient with moderate AD?"
9. "Discuss the evidence for dementia prevention."
10. "What is the NIA-AA ATN classification and how is it applied?"

Viva Points

Viva Point: Opening Statement: "Alzheimer's disease is a progressive neurodegenerative disorder and the most common cause of dementia, accounting for 60-80% of cases. It is characterised pathologically by extracellular amyloid-beta plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau protein. Clinically, it presents with insidious onset of episodic memory impairment, progressing to involve other cognitive domains and ultimately causing functional dependence."

Key Facts to Cite:

• Prevalence: 5-7% of adults > 65; doubles every 5 years; 30-50% of those > 85
• Lancet Commission 2020: 40% of dementia cases potentially preventable through addressing 12 modifiable risk factors
• CLARITY-AD trial: Lecanemab showed 27% slowing of decline at 18 months
• DOMINO trial: Supports continuing donepezil and adding memantine in moderate-severe disease
• NIA-AA 2018: ATN biomarker framework for AD diagnosis

Model Structure for Management: "My management would be holistic, encompassing pharmacological and non-pharmacological approaches, delivered within a multidisciplinary team framework:

1. Symptomatic treatment with AChE inhibitors for mild-moderate disease
2. Memantine addition in moderate-severe disease
3. Cognitive stimulation therapy — NICE recommended
4. Management of behavioural symptoms — non-pharmacological first
5. Caregiver support and education
6. Advance care planning while capacity remains
7. Referral to memory clinic for specialist support
8. Consider disease-modifying therapy if early-stage and appropriate"

Common Mistakes to Avoid

❌ Mistakes that fail candidates:

• Diagnosing AD without excluding reversible causes
• Missing red flags suggesting alternative diagnoses (rapid progression, early motor signs)
• Prescribing antipsychotics without attempting non-pharmacological measures first
• Forgetting the mortality risk of antipsychotics in dementia
• Not mentioning advance care planning
• Confusing APOE ε4 as diagnostic rather than a risk factor
• Describing outdated treatment approaches
• Failing to consider functional assessment alongside cognitive testing
• Not acknowledging the limitations of current treatments

Model Answers

Q: A 68-year-old man presents with 18 months of progressive forgetfulness. His wife reports he repeats questions and has got lost driving. How would you assess and investigate?

A: "I would approach this systematically, aiming to confirm cognitive impairment, characterise the pattern, exclude reversible causes, and establish the likely diagnosis.

History: I would take a detailed history from both patient and informant, focusing on cognitive symptoms across domains (memory, language, visuospatial, executive), timeline and progression, functional impact on ADLs and IADLs, behavioural changes, and relevant risk factors including family history and vascular risk factors.

Examination: General examination for nutritional status and systemic disease. Neurological examination to exclude focal signs. Formal cognitive assessment using validated tools — ACE-III or MoCA preferred for sensitivity.

Investigations: Blood tests to exclude reversible causes: FBC, U&Es, LFTs, calcium, glucose, TFTs, vitamin B12, folate. MRI brain to assess for hippocampal atrophy, exclude structural pathology, and evaluate vascular burden.

Further assessment: If diagnosis remains uncertain, I would consider specialist referral for CSF biomarkers or amyloid PET. In this case, the history of episodic memory impairment with gradual progression and functional impact would be consistent with probable Alzheimer's disease if investigations exclude alternative causes.

Management would include initiation of an AChE inhibitor, referral to memory services, cognitive stimulation therapy, and importantly, early discussion about driving notification to DVLA and establishment of Lasting Power of Attorney while capacity remains."

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12. Patient/Layperson Explanation

What is Alzheimer's Disease?

Alzheimer's disease is a condition that affects the brain and is the most common cause of dementia. "Dementia" means a decline in memory and thinking abilities that is severe enough to affect everyday life.

In Alzheimer's, abnormal proteins build up in the brain over many years. These proteins — called amyloid plaques and tau tangles — gradually damage and kill brain cells, starting in the areas involved in memory. Over time, this spreads to affect other parts of the brain.

Why Does It Happen?

We don't fully understand why some people develop Alzheimer's and others don't, but we know several factors that increase risk:

Factors you cannot change:

• Age (risk increases significantly after 65)
• Family history
• Certain genes (like APOE ε4)

Factors you may be able to influence:

• High blood pressure, diabetes, and obesity in middle age
• Smoking
• Lack of physical activity
• Hearing loss (if untreated)
• Social isolation
• Lower levels of education

Research suggests that up to 40% of dementia cases might be prevented or delayed by addressing these factors.

What Are the Symptoms?

Alzheimer's typically starts with memory problems, particularly difficulty remembering recent events and conversations. Other symptoms include:

• Repeating questions or stories
• Getting lost in familiar places
• Difficulty finding the right words
• Problems managing money or medications
• Personality changes (often becoming withdrawn)

As the condition progresses, people need increasing help with daily activities like dressing, bathing, and eventually eating.

How Is It Diagnosed?

There is no single test for Alzheimer's. Doctors diagnose it based on:

1. Symptoms and history — from the person and their family
2. Memory and thinking tests — structured questionnaires
3. Blood tests — to rule out other treatable causes (like thyroid problems or vitamin deficiencies)
4. Brain scans — usually an MRI, to look at brain structure

Sometimes, additional tests like spinal fluid analysis or specialised brain scans are needed.

What Treatments Are Available?

While there is no cure, treatments can help:

Medications:

• Drugs like donepezil, rivastigmine, or galantamine boost brain chemicals involved in memory. They work best in mild-to-moderate disease and can stabilise symptoms for a time.
• Memantine works differently and is used in moderate-to-severe disease.

New treatments:

• Recently, new medications that target the underlying brain changes have been approved in some countries. These may slow the disease in early stages but have significant risks and limitations.

Other approaches:

• Cognitive stimulation therapy — group activities that exercise the brain
• Physical exercise — helps maintain abilities
• Occupational therapy — helps people stay independent longer
• Support for carers — respite, education, financial help

What to Expect

Alzheimer's is a gradual condition. The average time from diagnosis to death is 4-8 years, but many people live longer, especially if diagnosed early.

Symptoms will slowly worsen, but the right support can help maintain quality of life. Planning early is important — for finances, legal matters (Power of Attorney), and future care wishes.

When to Seek Help

• If you're worried about your memory — see your GP
• If someone with dementia suddenly becomes more confused — this could be an infection or other illness (urgent)
• For support with caring — ask your GP or memory clinic about local services

Where to Get Support

• Alzheimer's Society (UK): www.alzheimers.org.uk — helpline 0333 150 3456
• Dementia UK / Admiral Nurses: www.dementiauk.org
• Age UK: www.ageuk.org.uk
• Carers UK: www.carersuk.org

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13. References

1. GBD 2019 Dementia Forecasting Collaborators. Estimation of the global prevalence of dementia in 2019 and forecasted prevalence in 2050: an analysis for the Global Burden of Disease Study 2019. Lancet Public Health. 2022;7(2):e105-e125. doi:10.1016/S2468-2667(21)00249-8

2. Serrano-Pozo A, Frosch MP, Masliah E, Hyman BT. Neuropathological alterations in Alzheimer disease. Cold Spring Harb Perspect Med. 2011;1(1):a006189. doi:10.1101/cshperspect.a006189

3. Scheltens P, De Strooper B, Kivipelto M, et al. Alzheimer's disease. Lancet. 2021;397(10284):1577-1590. doi:10.1016/S0140-6736(20)32205-4

4. Jack CR Jr, Bennett DA, Blennow K, et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease. Alzheimers Dement. 2018;14(4):535-562. doi:10.1016/j.jalz.2018.02.018

5. Hardy J, Selkoe DJ. The amyloid hypothesis of Alzheimer's disease: progress and problems on the road to therapeutics. Science. 2002;297(5580):353-356. doi:10.1126/science.1072994

6. Birks JS, Harvey RJ. Donepezil for dementia due to Alzheimer's disease. Cochrane Database Syst Rev. 2018;6(6):CD001190. doi:10.1002/14651858.CD001190.pub3

7. van Dyck CH, Swanson CJ, Aisen P, et al. Lecanemab in early Alzheimer's disease. N Engl J Med. 2023;388(1):9-21. doi:10.1056/NEJMoa2212948

8. Qiu C, Kivipelto M, von Strauss E. Epidemiology of Alzheimer's disease: occurrence, determinants, and strategies toward intervention. Dialogues Clin Neurosci. 2009;11(2):111-128. doi:10.31887/DCNS.2009.11.2/cqiu

9. Todd S, Barr S, Roberts M, Passmore AP. Survival in dementia and predictors of mortality: a review. Int J Geriatr Psychiatry. 2013;28(11):1109-1124. doi:10.1002/gps.3946

10. Liu CC, Kanekiyo T, Xu H, Bu G. Apolipoprotein E and Alzheimer disease: risk, mechanisms and therapy. Nat Rev Neurol. 2013;9(2):106-118. doi:10.1038/nrneurol.2012.263

11. Hampel H, Mesulam MM, Cuello AC, et al. The cholinergic system in the pathophysiology and treatment of Alzheimer's disease. Brain. 2018;141(7):1917-1933. doi:10.1093/brain/awy132

12. Wimo A, Seeher K, Cataldi R, et al. The worldwide costs of dementia in 2019. Alzheimers Dement. 2023;19(7):2865-2873. doi:10.1002/alz.12901

13. Alzheimer's Research UK. Dementia Statistics Hub. Available at: https://www.dementiastatistics.org. Accessed January 2025.

14. Satizabal CL, Beiser AS, Chouraki V, et al. Incidence of dementia over three decades in the Framingham Heart Study. N Engl J Med. 2016;374(6):523-532. doi:10.1056/NEJMoa1504327

15. Livingston G, Huntley J, Sommerlad A, et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet. 2020;396(10248):413-446. doi:10.1016/S0140-6736(20)30367-6

16. Hardy JA, Higgins GA. Alzheimer's disease: the amyloid cascade hypothesis. Science. 1992;256(5054):184-185. doi:10.1126/science.1566067

17. Braak H, Braak E. Neuropathological stageing of Alzheimer-related changes. Acta Neuropathol. 1991;82(4):239-259. doi:10.1007/BF00308809

18. Bellenguez C, Küçükali F, Jansen IE, et al. New insights into the genetic etiology of Alzheimer's disease and related dementias. Nat Genet. 2022;54(4):412-436. doi:10.1038/s41588-022-01024-z

19. Blennow K, Zetterberg H. Biomarkers for Alzheimer's disease: current status and prospects for the future. J Intern Med. 2018;284(6):643-663. doi:10.1111/joim.12816

20. Teunissen CE, Verberk IMW, Thijssen EH, et al. Blood-based biomarkers for Alzheimer's disease: towards clinical implementation. Lancet Neurol. 2022;21(1):66-77. doi:10.1016/S1474-4422(21)00361-6

21. McKhann GM, Knopman DS, Chertkow H, et al. The diagnosis of dementia due to Alzheimer's disease: recommendations from the National Institute on Aging-Alzheimer's Association workgroups. Alzheimers Dement. 2011;7(3):263-269. doi:10.1016/j.jalz.2011.03.005

22. National Institute for Health and Care Excellence. Dementia: assessment, management and support for people living with dementia and their carers. NICE guideline [NG97]. 2018, updated 2023. Available at: https://www.nice.org.uk/guidance/ng97

23. Howard R, McShane R, Lindesay J, et al. Donepezil and memantine for moderate-to-severe Alzheimer's disease. N Engl J Med. 2012;366(10):893-903. doi:10.1056/NEJMoa1106668

24. Ngandu T, Lehtisalo J, Solomon A, et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial. Lancet. 2015;385(9984):2255-2263. doi:10.1016/S0140-6736(15)60461-5

25. Sims JR, Zimmer JA, Evans CD, et al. Donanemab in early symptomatic Alzheimer disease: the TRAILBLAZER-ALZ 2 randomized clinical trial. JAMA. 2023;330(6):512-527. doi:10.1001/jama.2023.13239

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14. Additional Resources

Professional Resources

• Alzheimer's Disease International: www.alzint.org
• Alzheimer's Association (US): www.alz.org
• European Alzheimer's Disease Consortium
• NIA ADEAR Center: www.nia.nih.gov/alzheimers

Patient and Carer Resources (UK)

• Alzheimer's Society: www.alzheimers.org.uk
• Dementia UK / Admiral Nurses: www.dementiauk.org
• Carers UK: www.carersuk.org
• Age UK: www.ageuk.org.uk
• Young Dementia UK: www.youngdementiauk.org
• Rare Dementia Support (for atypical variants): www.raredementiasupport.org

Research and Clinical Trials

• Join Dementia Research: www.joindementiaresearch.nihr.ac.uk
• ClinicalTrials.gov: www.clinicaltrials.gov
• NIHR Dementia Translational Research Collaboration

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists. This content does not constitute medical advice for individual patients.