What Is Alzheimer's Disease? Symptoms, Stages, Diagnosis and Treatment

What Is Alzheimer's Disease?

Alzheimer's disease is a progressive neurodegenerative disease that can affect memory, thinking, reasoning, language and the ability to perform everyday activities.

It is the most common cause of dementia, particularly in older adults. Alzheimer's is not simply memory loss; as the disease progresses, decision-making, orientation, communication and independence can also be affected.

Characteristic biological changes include abnormal accumulation of beta-amyloid and tau-related neurofibrillary tangles, together with progressive damage and loss of neurons and their connections.

What Is the Difference Between Alzheimer's Disease and Dementia?

Dementia is a general clinical term describing a decline in memory, thinking, language, reasoning or other cognitive abilities severe enough to interfere with daily life.

Many diseases can cause dementia, including Alzheimer's disease, vascular dementia, Lewy body dementia, frontotemporal dementia and mixed dementia.

What Is Mild Cognitive Impairment?

Mild cognitive impairment (MCI) describes measurable memory or other cognitive difficulties that are greater than expected for age while the person remains largely independent in everyday activities.

MCI can represent an early clinical stage of Alzheimer's disease in some people, but not everyone with MCI will progress to Alzheimer's dementia.

What Are the Symptoms of Alzheimer's Disease?

Symptoms vary between individuals and usually develop gradually.

Common symptoms include:

• Forgetting recently learned information
• Repeating questions or stories
• Missing appointments or important events
• Difficulty finding words or following conversations
• Confusion about time or location
• Getting lost in familiar places
• Difficulty planning or solving problems
• Problems managing money or medications
• Misplacing objects in unusual places
• Reduced judgement
• Withdrawal from social activities
• Changes in mood, personality or behaviour

Memory loss is a common early feature, but language, visual-spatial ability or reasoning can be affected early in some patients.

What Are the Stages of Alzheimer's Disease?

Mild Alzheimer's Disease

A person may remain largely independent but have increasing problems with recent memory, planning, finding words, appointments, finances or other complex activities.

Moderate Alzheimer's Disease

Memory loss and confusion become more pronounced. Help may be needed with dressing, meals or other daily activities. Sleep disturbance, wandering, agitation, delusions or other behavioural changes may occur.

Severe Alzheimer's Disease

In advanced disease, communication, walking, eating and basic self-care may become severely impaired and continuous assistance may be required.

What Are the Risk Factors for Alzheimer's Disease?

Increasing age is the strongest known risk factor for Alzheimer's disease. However, Alzheimer's is not an inevitable consequence of ageing.

Factors that may influence risk include:

• Increasing age
• Family history
• Certain genetic variants
• Cardiovascular risk factors
• High blood pressure
• Diabetes
• Smoking
• Physical inactivity
• Certain health and sensory conditions such as hearing loss

Is Alzheimer's Disease Genetic?

Genetics can influence Alzheimer's risk, but most cases are not caused by a single gene.

APOE ε4 is an important genetic risk factor, but carrying APOE ε4 does not mean a person will definitely develop Alzheimer's.

Rare disease-causing variants in:

• APP
• PSEN1
• PSEN2

can cause some forms of early-onset familial Alzheimer's disease.

How Is Alzheimer's Disease Diagnosed?

Memory loss does not automatically mean Alzheimer's disease. Depression, sleep disorders, medication effects, thyroid disease, vitamin deficiencies, vascular disease and other neurological conditions may cause cognitive symptoms.

Assessment can include:

• Medical and medication history
• Information from a family member or close contact
• Assessment of everyday function
• Neurological examination
• Tests of memory, language, attention and executive function
• Blood tests
• Brain MRI or CT when appropriate
• Detailed neuropsychological testing in selected cases

What Are Alzheimer's Biomarkers?

Biomarkers can provide evidence of biological changes associated with Alzheimer's disease.

Selected patients may be assessed using:

• Amyloid and tau markers in cerebrospinal fluid
• Amyloid PET imaging
• Tau PET in selected settings
• Appropriately validated blood-based Alzheimer's biomarkers

These tests are not required for every person with forgetfulness. Their use depends on the clinical question, diagnostic uncertainty and whether the result would affect management.

How Is Alzheimer's Disease Treated?

There is currently no treatment that completely cures Alzheimer's disease.

However, treatment can include medicines that help manage symptoms and, in selected patients with early Alzheimer's, therapies that target underlying disease biology and can slow clinical progression.

Medicines for Alzheimer's Symptoms

Medicines that may be used include:

• Donepezil
• Rivastigmine
• Galantamine
• Memantine

These medicines do not cure Alzheimer's but can help temporarily improve or stabilise cognitive or functional symptoms in some people.

Depression, anxiety, sleep disturbance and agitation should also be assessed individually, with non-drug approaches generally considered before medication where appropriate.

Can Treatment Slow Alzheimer's Disease Progression?

Lecanemab and donanemab are anti-amyloid monoclonal antibodies approved by the U.S. FDA for treatment of selected patients in the early clinical stages of Alzheimer's disease.

Clinical trials showed that these therapies slowed cognitive and functional decline in some patients, but they do not cure Alzheimer's.

They require careful patient selection and confirmation of amyloid pathology.

What Is ARIA?

Anti-amyloid therapies can cause amyloid-related imaging abnormalities (ARIA), which may involve swelling or bleeding in the brain.

ARIA is often asymptomatic but can rarely be serious or life-threatening. MRI monitoring and careful assessment of individual risk are therefore important.

Non-Drug Approaches

Supportive approaches can include:

• Regular physical activity
• Maintaining structured daily routines
• Social engagement
• Mentally stimulating activities
• Supporting healthy sleep
• Addressing hearing and vision problems
• Making the home environment safer
• Education and support for caregivers

Can Alzheimer's Risk Be Reduced?

There is no single proven strategy that guarantees prevention of Alzheimer's disease.

Measures that support cardiovascular and brain health include regular physical activity, management of blood pressure and diabetes, avoiding smoking, a balanced diet, social engagement and assessment of treatable problems such as hearing loss.

When Should You See a Doctor?

Memory or thinking problems that begin to interfere with everyday activities should not automatically be attributed to ageing.

Assessment may be appropriate for:

• Repeated questions
• Getting lost in familiar places
• New difficulty managing money or medication
• Progressive word-finding difficulty
• Marked personality or behavioural change
• Decline in everyday functional abilities

Frequently Asked Questions

References

1. Academic Hospital. Alzheimer's Disease
2. National Institute on Aging. What Is Alzheimer's Disease?
3. National Institute on Aging. How Is Alzheimer's Disease Diagnosed?
4. National Institute on Aging. How Is Alzheimer's Disease Treated?
5. National Institute on Aging. Alzheimer's Disease Genetics Fact Sheet
6. U.S. Food and Drug Administration. FDA Approves Donanemab for Alzheimer's Disease