Dementia - Alzheimer's disease

Alzheimer’s disease is a physical disease of the brain in which brain cells are progressively damaged, leading to dementia. It is the most common form of dementia, accounting for about two thirds of cases. The brain degeneration that occurs in Alzheimer’s disease affects memory, thinking skills, emotions, behaviour and mood. As a result, a person’s ability to carry out everyday activities gradually becomes impaired.

As the disease progresses, symptoms worsen#

Alzheimer’s disease usually starts slowly, and the symptoms can be very subtle in the early stages. As the disease advances, the symptoms become more noticeable and interfere with daily life. The disease affects each person differently, and the symptoms vary from one individual to another.

Common features include:

• changes in behaviour, personality and mood that shift as the disease progresses
• abilities that may fluctuate from day to day, or even within a single day, because different areas of the brain are affected
• symptoms that can become worse in times of stress, fatigue or ill health

The disease progresses from mild Alzheimer’s disease (which can be so subtle that it may only be recognised in hindsight) to moderate Alzheimer’s disease, and then to severe Alzheimer’s disease. The rate of progression between these stages differs from person to person.

What causes Alzheimer’s disease#

Researchers are steadily learning more about the chemical changes that damage brain cells in Alzheimer’s disease. Apart from the small number of people with familial Alzheimer’s disease, it is not known why some people develop the condition and others do not. It is likely that several factors contribute, including environmental, genetic and health factors.

Alzheimer’s disease is characterised by specific changes in the brain. These include the formation of amyloid plaques (fibrous patches) and neurofibrillary tangles (strands of proteins). An abnormal build-up of a protein called beta-amyloid causes amyloid plaques to form outside the brain cells. Inside the brain cells, another protein called tau builds up and causes neurofibrillary tangles.

These protein accumulations disrupt messages within the brain by damaging the connections between brain cells. The brain cells eventually die and brain volume shrinks. These changes happen gradually and begin many years (on average around 15 years) before the symptoms of Alzheimer’s disease appear. The brain is able to compensate for the early damage, but eventually the damage becomes too great and brain function is affected. Alzheimer’s disease can affect adults of either sex.

Sporadic Alzheimer’s disease#

The vast majority of cases are not caused by known changes to specific genes. This type is called sporadic Alzheimer’s disease, and it accounts for more than 90 per cent of cases. Most cases occur in people over the age of 65, and the cause is unknown.

Having a close family member with the condition increases risk by a small amount. Although there are no known changes to specific genes in sporadic Alzheimer’s disease, having one or two copies of a gene called apolipoprotein E4 (ApoE4) can increase the risk. This gene does not make it certain that a person will develop Alzheimer’s disease, and some people with ApoE4 never develop it.

Familial Alzheimer’s disease#

Familial Alzheimer’s disease accounts for less than five per cent of cases. This rare type is caused by changes in particular genes. The age of onset is earlier than for sporadic Alzheimer’s disease, with symptoms often appearing when the person is between 40 and 60.

The genetic changes affect the genes presenilin 1, presenilin 2 and amyloid precursor protein (APP). These changes increase production of the protein beta-amyloid found in amyloid plaques. Genetic testing can identify the presence of gene changes that cause familial Alzheimer’s disease. The test can tell whether a person has familial Alzheimer’s disease, and whether a child has inherited the changed gene from a parent and will develop the disease in future. The test cannot determine when symptoms will begin, although the age of onset is usually similar to that of the parent.

Down syndrome and Alzheimer’s disease#

People with Down syndrome have a third copy of chromosome 21, instead of the usual two copies. This genetic change causes a collection of characteristics, including intellectual disability and some common physical traits. The APP gene, which leads to the production of the beta-amyloid protein present in Alzheimer’s plaques, is located on chromosome 21. This means that people with Down syndrome make one and a half times the amount of APP and, as a result, more beta-amyloid. This appears to be the reason the brain changes typical of Alzheimer’s disease tend to appear earlier in people with Down syndrome.

Risk factors#

Understanding the risk factors for Alzheimer’s disease can help you make decisions about strategies that may reduce your risk. The risk factors fall into a number of types.

Age is a risk factor that cannot be controlled (a non-modifiable risk factor). The likelihood of developing Alzheimer’s disease increases with age.

Genetics is another risk factor that cannot be controlled. The genetics of Alzheimer’s disease is not fully understood, but there are genetic changes in familial Alzheimer’s disease and Down syndrome, as well as susceptibility genes for sporadic Alzheimer’s disease.

Brain-related risk factors that can be influenced include:

• mental activity – regularly challenging your brain with mentally stimulating activities, through education, work or leisure, is associated with a lower risk of decline in thinking abilities
• social activity – taking part in social activities, and staying connected with your community and friends, is associated with a lower risk of dementia

Body-related risk factors that can be influenced include:

• alcohol – too much alcohol can damage the brain and is linked to an increased risk of dementia
• physical activity – regular exercise is associated with better brain function and a reduced risk of decline in thinking abilities
• diet – the available evidence suggests a healthy diet can play a role in promoting brain health

Heart-related risk factors that can be influenced include problems that affect the heart and blood vessels, which are associated with an increased risk of cognitive impairment, and smoking, which is a risk factor for Alzheimer’s disease. Some studies suggest that a history of passive smoking may also increase risk.

Diagnosis#

Consulting a doctor at an early stage is important. Only a doctor can diagnose Alzheimer’s disease. It is important to rule out other conditions that can mimic the symptoms, such as brain tumours, depression or some types of malnutrition. A complete medical assessment may identify a treatable condition and ensure it is treated correctly, or it may confirm the presence of Alzheimer’s disease.

The range of tests used may include:

• medical history
• physical examination
• blood and urine tests
• memory, thinking and other tests of cognitive ability (neuropsychological or cognitive tests)
• brain imaging

People with Alzheimer’s disease differ in the patterns of problems they experience and in the speed with which their abilities decline. Their abilities may change from day to day, or even within the same day. What is certain is that abilities will deteriorate – sometimes rapidly over a few months, and sometimes more slowly, over a number of years.

Stages of Alzheimer’s disease#

Some features of Alzheimer’s disease are grouped into three stages. Not all of these features will be present in every person, nor will every person go through every stage, but the stages are still a useful way to describe how the disease progresses. At all stages, treatments and support are available to help make sure of the best possible quality of life for everyone affected.

Mild Alzheimer’s disease#

This stage is often only apparent in hindsight. At the time, it may be missed or put down to old age or overwork, because the onset is very gradual. During this stage, the person may:

• appear more apathetic, with less sparkle
• lose interest in hobbies or activities
• be less willing to try new things, and less able to adapt to change
• be slower to grasp complex ideas and take longer over routine tasks
• become more forgetful of details of recent events
• become confused or disoriented as to time and place, and become lost away from familiar surroundings
• be more likely to repeat themselves or lose the thread of a conversation
• be more irritable or upset if they fail at something
• have difficulty shopping, preparing meals or managing finances

Moderate Alzheimer’s disease#

At this stage the person’s problems are more obvious and disabling. A person with moderate Alzheimer’s disease is not able to live independently and needs significant day-to-day support. They may:

• be very forgetful of current or recent events, while memory of the distant past seems better
• become angry, upset or distressed through frustration
• be confused about time and place, and become lost more easily
• forget the names of family or friends, or confuse one family member with another
• forget saucepans and kettles on the stove, or leave the gas lit
• be less able to perform simple calculations
• show poor judgement and make poor decisions
• wander around streets, perhaps at night, sometimes becoming lost
• behave inappropriately – for example, going outdoors in their nightwear
• see or hear things that are not there, or become suspicious of others
• become very repetitive
• be neglectful of hygiene or eating
• be unable to choose clothing appropriate for the weather or occasion

Severe Alzheimer’s disease#

At this stage the person is severely disabled and needs continuous care for all daily activities. They may:

• be unable to remember current or recent events – for example, forgetting that they have just had a meal, or being unable to recall where they live
• be unable to recall important events or facts from their early life
• show confused recognition of friends and family
• fail to recognise everyday objects
• lose the ability to understand or use speech
• need help with eating, washing, bathing, brushing teeth, toileting and dressing
• be incontinent
• be disturbed at night, restless or fidgety
• call out frequently or become aggressive
• have difficulty walking and other movement problems, such as rigidity

Some abilities remain even as many are lost. The person may keep their sense of touch and hearing, and their ability to respond to emotion, even in the final stages. Immobility eventually becomes permanent, and in the final stages the person will be bedridden and unable to sit up independently. As a terminal illness, Alzheimer’s disease progresses until the end of life, with extensive care required.

Treatment#

There is no cure, and no treatment that can stop Alzheimer’s disease from progressing. Some medications can help to stabilise or slow the decline in memory and thinking for a time, such as cholinesterase inhibitors and memantine. Other medications may help with secondary symptoms such as depression, anxiety and sleep disturbances.

It is important to remember that all medications have side effects#

People with Alzheimer’s disease may take a number of medications, and your doctor can help you understand how the different medications might interact with each other.

Non-medication therapies, staying active and socially connected, and managing stress can all help people with Alzheimer’s disease. Education and professional support are important for people with the condition and for their families and carers.

Key points#

• Alzheimer’s disease is a physical disease of the brain with progressive damage to brain cells that causes dementia
• It is the most common form of dementia, accounting for about two thirds of cases
• As the disease progresses, symptoms worsen
• Alzheimer’s disease typically starts slowly, and the symptoms can be very subtle in the early stages
• As the disease progresses, symptoms become more noticeable and interfere with daily life

Where to get help#