Alzheimer's disease

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 7 Apr 2025

Last updated: 05 Sep 2023

Alzheimer's disease (AD) is a chronic, progressive neurodegenerative disorder characterised by a global, non-reversible impairment in cerebral functioning.

AD is characterised by memory loss, loss of social and occupational functioning, diminished executive function, speech and motor deficits, personality change, and behavioural and psychological disturbance.

It has a deteriorating course over up to 8-10 years.

Brain lesions are marked by neurofibrillary tangles, senile plaques, neuronal loss and brain atrophy, with defects in acetylcholine synthesis at the cellular level.

Treatment requires a multidisciplinary approach with increasing emphasis on behavioural and psychological symptoms.

Psychosocial interventions and carer support are key to managing disease course. Carer support groups are beneficial to carers and should be considered, where available.

Definition

Alzheimer's disease (AD) is a chronic neurodegenerative disease with an insidious onset and progressive but slow decline. AD is the most common type of dementia.[1][2] It often co-exists with other forms of dementia, particularly vascular dementia (mixed-type dementia). The histopathology of AD is characterised by senile plaques, neurofibrillary tangles, and neuronal loss. The hallmark symptoms are memory loss, impairment of daily activities, and neurobehavioural abnormalities. Definition of severity varies according to country, but a commonly accepted categorisation is mild, moderate, and severe. The Mini-Mental State Examination can be used as a guide to cognitive impairment, but education, language, and any other relevant factors must be taken into consideration when interpreting scores.

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History and exam

Key diagnostic factors

presence of risk factors
memory loss
disorientation
nominal dysphasia
misplacing items/getting lost
apathy
decline in activities of daily living and instrumental activities of daily living (IADLs)
personality change
unremarkable initial physical examination

Full details

Other diagnostic factors

mood changes
poor abstract thinking
constructional dyspraxia
prosopagnosia
autoprosopagnosia

Full details

Risk factors

advanced age
family history
genetics
Down's syndrome
cerebrovascular disease
lifestyle factors and medications
less than secondary school education
traumatic brain injury
depression
hearing loss
hyperlipidaemia
female sex
elevated plasma homocysteine level
artificially sweetened soft drink consumption

Full details

Diagnostic investigations

1st investigations to order

bedside cognitive testing
FBC
metabolic panel
serum thyroid-stimulating hormone (TSH)
serum vitamin B12
urine drug screen
CT
MRI

Full details

Investigations to consider

cerebrospinal fluid (CSF) analysis
serum rapid plasma reagin/Venereal Disease Research Laboratory (VDRL)
serum HIV
formal neuropsychological testing
genetic testing
fluorodeoxyglucose-PET (FDG-PET)
single-photon emission CT (SPECT)
electroencephalogram (EEG)

Full details

Emerging tests

amyloid-PET

Treatment algorithm

ONGOING

all patients

Contributors

Authors

Judith Neugroschl, MD

Associate Professor of Psychiatry

Alzheimer's Disease Research Center

Icahn School of Medicine at Mount Sinai

New York

Disclosures

JN participates in research funded by National Institutes for Health (NIH) grants. The Alzheimer's Disease Research Center is a site for clinical research but JN is not the site Principal Investigator, has no role in purchasing nor choosing the studies, and gains no compensation if they succeed. JN helps to edit the Focus on Healthy Aging Alzheimer's yearly report.

Acknowledgements

Dr Judith Neugroschl would like to gratefully acknowledge Dr Brandy R. Matthews, Dr Asif S. Bhutto, and Dr Julie K. Gammack, the previous contributors to this topic.

Disclosures

BRM, ASB, and JKG declare that they have no competing interests.

Peer reviewers

Roy J. Goldberg, MD, FACP, AGSF, CMD

Medical Director

Kings Harbor Multicare Center

New York

Disclosures

RJG declares that he has no competing interests.

Philip Scheltens, MD, PhD

Professor of Neurology

Department of Neurology/Alzheimer Center

VU University Medical Center

Amsterdam

The Netherlands

Disclosures

PS declares that he has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

GBD 2016 Dementia Collaborators. Global, regional, and national burden of Alzheimer's disease and other dementias, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet Neurol. 2019 Jan;18(1):88-106.Full text Abstract

Livingston G, Huntley J, Sommerlad A, et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet. 2020 Aug 8;396(10248):413-46.Full text Abstract

Fink HA, Linskens EJ, Silverman PC, et al. Accuracy of biomarker testing for neuropathologically defined Alzheimer disease in older adults with dementia. Ann Intern Med. 2020 May 19;172(10):669-77. Abstract

Birks JS, Harvey RJ. Donepezil for dementia due to Alzheimer's disease. Cochrane Database Syst Rev. 2018 Jun 18;(6):CD001190.Full text Abstract

Birks JS, Chong LY, Grimley Evans J. Rivastigmine for Alzheimer's disease. Cochrane Database Syst Rev. 2015 Sep 22;(9):CD001191.Full text Abstract

McShane R, Westby MJ, Roberts E, et al. Memantine for dementia. Cochrane Database Syst Rev. 2019 Mar 20;(3):CD003154.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials
- Delirium
- Depression
- Vascular dementia
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Guidelines
- Clinical guidance in neuropalliative care: an AAN position statement
- Ethical considerations in dementia diagnosis and care: an AAN position statement
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Patient information
Alzheimer's disease and other kinds of dementia
Caring for someone with dementia
More Patient information
Calculators
Geriatric Depression Scale
More Calculators
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Alzheimer's disease

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Emerging tests

Treatment algorithm

all patients

Contributors

Authors

Judith Neugroschl, MD

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Roy J. Goldberg, MD, FACP, AGSF, CMD

Disclosures

Philip Scheltens, MD, PhD

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Calculators

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice