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Alzheimer’s Disease

Written by Ada’s Medical Knowledge Team

Updated on

What is Alzheimer’s disease?

Alzheimer’s disease is a brain condition in which certain mental functions such as memory or reasoning are lost over time. It is the most common form of dementia. 1

The exact cause is unknown, but clumps of protein developing around the brain cells is a key feature of Alzheimer’s. 2

The condition is unlikely to affect people aged under 65. When this does occur, it is known as early-onset Alzheimer’s. Eating a healthy diet, getting plenty of exercise and avoiding smoking tobacco products are thought to lower the risk of Alzheimer’s disease. 1 One in 10 people aged over 65 in the U.S. are thought to have the condition.

Diagnosis is based on the symptoms. Doctors can also assess a person’s mental functioning by using written tests and interviews. Brain scans may also be used to rule out other conditions that cause similar symptoms to Alzheimer’s disease, such as head trauma or the effect of repeated concussions. Similar symptoms may also be caused by other types of dementia, which can sometimes affect a person at the same time as Alzheimer’s. 3

Alzheimer’s disease cannot be cured. However, a person may experience some relief from their symptoms after taking medication such as cholinesterase inhibitors. Therapy is also often recommended to help a person come to terms with the loss of their mental function. 1 4


Which symptoms of Alzheimer’s disease are evident often vary from person to person. It can depend on a number of factors, such as age, general health and how far the condition has progressed.

The changes in the brain that cause Alzheimer’s will start occurring some time before any symptoms appear. While the exact symptoms vary from person to person, one of the first signs of the disease is usually memory difficulties. 5

Alzheimer’s disease will usually shorten a person’s lifespan. However, death is often directly caused by other conditions or even old age. 1

If you are concerned about the welfare of yourself or a loved one, check your symptoms with the Ada app.

Preclinical Alzheimer’s

A person with preclinical Alzheimer’s is unlikely to show any symptoms, even when they are being tested. At this stage, the condition is beginning to affect a person’s brain, but not enough to cause any noticeable effect. 1

Typical early symptoms

The first symptoms of Alzheimer’s are likely to include: 1 5 6

  • Loss of memory, specifically events that happened recently
  • The above may lead to a person needing to ask the same questions repeatedly
  • Needing more time to complete day-to-day tasks, for example handling money and paying bills
  • Visual complaints, such as difficulty reading and driving

Typical symptoms along the course of Alzheimer’s

Along the course of Alzheimer’s, the following symptoms may be experienced: 1 5

  • Worsening memory loss and increasing confusion
  • Shortening attention span
  • Changes to usual personality and behaviour
  • A growing reluctance to use initiative and try new things
  • Increased emotion and anxiety
  • Difficulty recognizing family and friends
  • Increased difficulty with reading, writing and mathematical questions
  • Difficulty learning new things
  • The way to complete day-to-day tasks, such as getting dressed, may be forgotten
  • Restlessness, agitation and annoyance
  • Hallucinations, delusions and paranoia
  • Lessened ability to think things through logically
  • The need to wander, especially late in the day or in the evening
  • Performing repetitive actions or repeating the same information when speaking
  • An inability to control impulses, e.g. saying inappropriate things to others
  • Muscular twitching

Typical late symptoms

After a person reaches late-stage Alzheimer’s, they effectively lose independence and will require a full-time carer. The affected person will be unable to communicate effectively, and their personality may seem to disappear. Towards the end of their life, it is possible that they will spend much of their time in bed or otherwise at rest. Symptoms associated with late-stage Alzheimer’s can include: 1 5

  • Weight loss
  • Seizures
  • Skin infections
  • Difficulty swallowing
  • Loss of bladder control
  • An inability to speak coherently
  • An increased need to sleep


The symptoms of Alzheimer’s disease are directly caused by the cells that transmit information to and from the brain, known as neurons, ceasing to function and eventually dying. However, what causes this to occur is not yet known. 7

The first neurons that begin to die are usually located in the hippocampus, a part of the brain that is involved in forming memories.

Along with neuron death, a hallmark of the condition is the development of clumps of protein in the brain, known as plaques, as well as tangles of fibers called tau. The relationship between tau, plaques and neuron death is not clearly understood.

It is not unusual for people to be diagnosed with another dementia, such as vascular dementia, alongside Alzheimer’s. This is known as mixed dementia. 8

Alzheimer’s disease risk factors

The primary risk factor for Alzheimer’s is age. Most people affected by Alzheimer’s do not begin to show symptoms until they are over 65. 9 Other circumstances that may contribute to the development of Alzheimer’s disease include genetic and lifestyle factors.

Genetic factors

About one in 20 cases is caused by a person inheriting certain genes from their parents. People with this genetically-inherited form of the condition are almost certain to develop early-onset Alzheimer’s, which is when symptoms of the disease show before the affected person is 65. 9 10

No specific gene has been discovered that causes late-onset Alzheimer’s. However, inheriting a type of gene variation known as apolipoprotein E 4, makes developing the condition more likely though not certain. The majority of Alzheimer’s cases are known as sporadic, which means that genetics are not a factor.

Nevertheless, having a direct relation that has been affected by dementia increases the risk of a person developing Alzheimer’s by between 10 and 30 percent. If a person’s family includes two or more siblings that have been diagnosed with Alzheimer’s disease, then they are three times as likely to be affected by the condition compared with the general population. 11

Lifestyle factors

There appears to be a link between diseases of the vascular system, the network that transports blood around the body, and Alzheimer’s disease. Vascular diseases include coronary artery disease and peripheral vascular disease.

As a result, avoiding some of the potential causes for unhealthy blood vessels is possibly the best way to protect oneself against Alzheimer’s disease. 1 This includes: ref1 10 12 13

  • Getting plenty of exercise
  • Staying in shape, e.g. through a healthy diet
  • Avoiding smoking tobacco products
  • Avoiding consuming too much alcohol

Other risk factors

These include: 9 10 14

  • Down’s syndrome, also known as trisomy 21. Around half of people with this condition will develop Alzheimer’s disease
  • Traumatic brain injury
  • Insulin resistance, which can also lead to Type 2 diabetes
  • Depression
  • Hypertension
  • Obesity


There is no definitive test for Alzheimer’s disease. Instead, a doctor will usually make a diagnosis based on the symptoms and several tests. A family member or friend may need to be involved to be asked questions about the severity of symptoms, as the person affected may not be the best guide in respect of how they are behaving. 15

There are plenty of other conditions that can cause similar symptoms to Alzheimer’s. Chronic traumatic encephalopathy, which is brain damage linked to multiple concussions, and Parkinson’s disease are two such examples. A doctor may run blood tests and brain scans to discover whether a condition other than Alzheimer’s is responsible for the affected person’s symptoms or if they have another condition in addition to Alzheimer’s. 13 16

Cognitive tests

A short test that assesses a person’s mental function will often be used to help a doctor in their diagnosis. The test will generally look at: 17

  • Problem solving
  • Attention span
  • Memory
  • Counting
  • Language

This test is known as a mini-mental state exam or Montreal Cognitive Assessment (MoCA).

Neuropsychological tests

This is a longer, more extensive test, which may be carried out by a type of doctor known as a neuropsychologist. A neuropsychological test usually takes several hours and will assess the following: 18 19

  • Memory
  • Attention span
  • Mental processing
  • Mental reasoning
  • Judgement
  • Visuospatial function, i.e. the way a person relates what they see to the world around them

Brain scans

People suspected of being affected by Alzheimer’s will likely undergo brain scans, which allow doctors to look in detail at an image of the brain. This will be one of the following: 20

  • A CT scan of the head, which uses X-Rays to create the image
  • An MRI scan, which uses magnetic fields and radio waves to create the image

Although there may be some evidence of Alzheimer’s in the image produced by the scan, this test will mostly be to rule out other possible causes of the symptoms, such as stroke or a brain tumor.

Treating Alzheimer’s

Treatment for Alzheimer’s is focused on suppressing symptoms and maintaining brain function for as long as possible. No medication currently exists to stop the progression of the disease.

Medication for Alzheimer’s symptoms

There are two medications that are used to suppress Alzheimer’s symptoms. Treatment is not always effective, but for some people these drugs can bring relief from symptoms and allow a person to maintain a higher level of mental functioning for longer than they otherwise would have.

People affected by mild to moderate Alzheimer’s will generally be given cholinesterase inhibitors. These slow the breakdown of acetylcholine, a chemical in the brain that helps neurons send messages to other cells. 21

As Alzheimer’s progresses, a doctor may prescribe memantine. This drug makes sure that the buildup of calcium in between brain cells, too much of which can cause nerve damage, is regulated. 23

Cholinesterase inhibitors and memantine can sometimes be taken at the same time. A doctor will generally advise whether this is appropriate,

The difficulties a person faces during Alzheimer’s will often cause a number of mood symptoms, such as depression or anxiety. There are a number of medications which may be recommended to help with these issues. These include: 24

  • Antidepressants
  • Antipsychotics
  • Anti-anxiety aids
  • Medication to assist with sleeping

Therapies and mental support

An occupational therapist may be able to help someone with Alzheimer’s or the person helping care for them adjust to some of the changes that the condition can cause. For example, a weekly pill box and the use of alarms and reminders can be a big help. 25

Cognitive stimulation therapy may also be recommended. This includes structured sessions in which people complete tasks that stimulate thinking and memory. This has been shown to be beneficial to people with mild to moderate dementia. 26

Cognitive behavioural therapy (CBT) and other talking therapies that assist with anxiety and depression may be recommended for people affected by those symptoms because of Alzheimer’s. 25

Keeping active

Keeping active is advisable during Alzheimer’s, if possible. 25 People with a high level of fitness seem to have some protective effects against the progression of the disease. 21 Exercise is also generally beneficial to a person’s physical and mental health.


Q:What trials and research are going on for Alzheimer’s disease?
A: The uncertain cause of brain deterioration during Alzheimer’s disease has meant that attempts to find a treatment to cure or halt symptoms has been difficult. Research areas have included: 27

  • Attempt to slow down or stop the formation of plaques (anti-amyloid therapy)
  • Attempts to minimize the negative effects of tau
  • Attempts to protect the brain from atoms called free radicals that have been linked to Alzheimer’s disease
  • Treatment with Vitamin E to slow some of the processes linked to Alzheimer’s

Vitamin E trials have shown some success at slowing the progression of the disease, though the effect is moderate. The other trials have not yet found an effective treatment.

A recent study claims to have shown a link between the bacteria behind gum disease and Alzheimer’s disease. Research into this line of inquiry is ongoing. 28

Q: Are people who have had a depressive episode more likely to develop Alzheimer’s?
A: The majority of people that have experienced depression will not go on to be diagnosed with Alzheimer’s disease. However, several studies in the U.S. and elsewhere do suggest that a person affected by depression at some point in their life does have a higher risk of developing Alzheimer’s than someone who has never had a depressive episode. 29 The link between depression and Alzheimer’s remains poorly understood.

Depression also often develops once a person is diagnosed with Alzheimer’s disease. Antidepressant medication and therapy help a person with the symptoms of a depressive episode. 24 26 25

Q: Is Alzheimer’s disease hereditary?
A: About one in 20 cases of Alzheimer’s is a version of the disease inherited directly from a person’s parents. This type of Alzheimer’s is almost always early-onset, meaning it affects people when they are younger than 65. Besides this rare version of Alzheimer’s disease, there are no genes that are known to directly cause the condition.

Read more about Alzheimer’s disease risk factors »

Q: What support exists for people experiencing Alzheimer’s disease?
A: There are many online resources offering help on specific aspects of Alzheimer’s disease, such as the U.S. government’s ADEAR center. In-person support groups such as those organized by the Alzheimer’s Association and the Alzheimer’s Foundation of America help those affected by the condition, as well as carers, in dealing with the disease.

How Is Alzheimer's Disease Treated?.” 01 April, 2018. Accessed: 25 January, 2019.