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Alzheimer’s disease


Expert reviewer, Professor Graham Stokes, psychologist and dementia specialist
Next review due December 2019

Alzheimer’s disease is the most common type of dementia, making up more than six out of 10 cases (60%).

We don’t understand in much detail what causes Alzheimer’s. To some extent, it can run in families, although this is truer for early onset dementia (before age 55).

Alzheimer’s is more likely as you get older. About one in every 100 people aged 65 have Alzheimer’s. This rises to 40 out of every 100 by age 85. More women have it than men, but that’s because they generally live longer so there are more women at older ages.

About Alzheimer's disease

Alzheimer's disease is a form of dementia. Dementia refers to a set of symptoms, including problems with thinking, reasoning, learning, memory and language, and difficulties with daily activities. Alzheimer’s signs usually come on gradually. Early Alzheimer's symptoms include worsening memory, increasing difficulty coping with daily tasks and irritability. There are differences between Alzheimer's disease and other forms of dementia.

Alzheimer’s gradually worsens over time, although this can sometimes be a very slow process. There can also be ‘plateaus’ when the decline stops for periods of time. Medicines are now available that can slow the rate of decline in some people.

Symptoms of Alzheimer’s disease

It can be difficult to diagnose Alzheimer’s disease (Alzheimer’s). In the early stages, Alzheimer's symptoms can be subtle and come on slowly, making it difficult to diagnose. It’s very important for doctors to get as much information as possible from family and friends who see the person regularly. They can help to explain exactly what has changed and over what period of time.

The doctor will also want to know whether anyone else in the family has had any form of dementia. Having Alzheimer’s in the family is a known risk factor, particularly if anyone developed it at a young age (before age 65).

Often one of the first Alzheimer's symptoms is difficulty remembering times and dates and taking in new information, such as learning to do something new. Other Alzheimer's symptoms that may appear first include memory lapses, such as:

  • forgetting names of people and places
  • difficulty finding words for things
  • not remembering recent events
  • forgetting appointments

There may be signs of changes in behaviour. The person may become more withdrawn and lose interest in their usual activities and hobbies.

As the condition worsens, they may have:

  • greater difficulty planning and making decisions
  • difficulty with language
  • confusion
  • difficulty carrying out instructions for specific tasks

In the later stages of Alzheimer’s, symptoms such as confusion and disorientation get worse. At this stage of Alzheimer's disease, people may walk and get lost. Other symptoms can include:

  • psychiatric symptoms such as hallucinations and delusions
  • depression
  • agitation and aggression
  • incontinence
  • loss of interest in eating and drinking

It’s important to remember that changes in behaviour and mood, such as depression or agitation, may be a reaction to living in unsupportive surroundings. They’re not direct ‘symptoms’ of Alzheimer’s disease or another form of dementia.

How Alzheimer’s disease develops

Alzheimer’s is a long-term condition that gradually worsens over time. This can be a very slow process in some people, but the progression of Alzheimer's symptoms varies a great deal from person to person. In some cases, it can be as quick as five years. In others, the decline may take 20 years, with long periods where there is no apparent change. Doctors call these periods where the disease doesn’t get worse ‘plateaus’.

Early on, people with Alzheimer’s may be able to manage with a little support from family and friends, just needing a bit of supervision with medicines and managing finances. Finding that an older relative’s finances are in a bit of a mess can be the first sign that something is not quite right, leading to the Alzheimer’s diagnosis.

Some of the first activities to become a problem are tasks that need a bit of forward planning, such as cooking and shopping. These problems are caused by difficulties with memory and orientation.

As the condition progresses, the person will have more difficulty managing day-to-day life. They’re likely to need help with more basic daily care, such as washing and dressing. Because the condition worsens over time, eventually many people need to be looked after all the time, which is often only possible in residential care.

As with many long-term illnesses, there can be complications with Alzheimer’s. People with Alzheimer’s have a higher-than-average risk of infections. They may be prone to bladder (urinary tract) infections. Difficulty swallowing can lead to small amounts of food or drink being breathed in. This can lead to pneumonia.

Urinary incontinence is common in the later stages of all forms of dementia. This sometimes means that the person needs a tube to drain their bladder (an indwelling catheter), which can increase the risk of infection.

It is important to pick up on the signs of a chest or urine infection. If untreated, these can become life-threatening.

Causes of Alzheimer’s disease

Doctors don’t fully understand what causes Alzheimer’s disease. There are some signs that help to explain how it develops.

Alzheimer’s causes some areas of the brain to shrink, while other areas seem normal. The shrinkage is caused by nerve cells dying in some areas of the brain. The brain of someone with Alzheimer’s typically weighs about 100–200 grams less than a normal average brain.


Image of two brain scans showing changes in the brain during Alzheimer's disease

Two brain scans showing changes in the brain during Alzheimer's disease.
In the right-hand image, the white parts are where cells have died in some areas of the brain.

This shrinking offers some insight into what causes Alzheimer's disease. Inside brain cells damaged by Alzheimer’s, there are twists and knots of protein fibres that usually run in straight lines in normal cells. These fibres are usually the ‘transport system’ of the cell. Once they become tangled, important molecules can't easily move through the cell and it dies.

The more of these tangles there are, the worse the Alzheimer’s symptoms generally become. So, while doctors still don't know exactly what causes the death of brain cells in Alzheimer’s, they strongly suspect that the tangles are one cause.

Another suspected cause of Alzheimer's disease is an abnormal build-up of protein in the brain. Normal nerve cells work by sending chemical signals to each other via ‘chemical messengers’. When you look at brain tissue affected by Alzheimer’s under a microscope, you can see fragments of protein collecting between the nerve cells. These may block signals between nerve fibres in the brain, so the nerve cells can no longer work.

Medicines for Alzheimer’s disease

Unfortunately, there is no cure for Alzheimer’s disease as yet. There are now medicines available to treat the symptoms of Alzheimer’s. They don’t treat the underlying progressive illness. The aim of this treatment is to help to slow memory loss, and to keep the person with Alzheimer’s managing their daily lives as much as possible.


Medicines for early-stage Alzheimer’s

The doctor is likely to prescribe one of the three medicines available:

  • donepezil (Aricept)
  • galantamine (Reminyl)
  • rivastigmine (Exelon)

The names in brackets are the brand names. These are all the same type of drug, called acetylcholinesterase inhibitors. (Note that these are not the same as ACE inhibitors, which are prescribed for high blood pressure.) Acetylcholinesterase inhibitors stop an enzyme called acetylcholinesterase from breaking down the ‘chemical messenger’ acetylcholine in the brain. This helps the nerve cells in the brain to communicate with each other.

All these medicines seem to work as well as each other. There’s evidence that they can slow down the development of Alzheimer’s symptoms for a year or two. Unfortunately, they can’t cure it and there’s no evidence that they help people to live any longer. In particular, there can be a noticeable improvement in memory, but this won’t be the case for most people.

These medicines can’t help with advanced Alzheimer’s. It is best to start taking them as soon as the condition is diagnosed, in the early stages. They have to be prescribed by a specialist and are either tablets or capsules. You take Aricept once daily and the other two medicines twice daily. Exelon also comes as a stick-on patch that you change once every 24 hours. This can be easier for some families to manage than tablets.

The dose of all these medicines is gradually increased over the first month. This is to try and get the most benefit with the fewest side-effects. The most common side-effects are generally feeling sick, vomiting and diarrhoea. Skin patches may cause fewer side-effects than tablets or capsules.

A few months after the person is on a stable dose of their Alzheimer’s medicine, the doctor will examine them to see if their condition is stable, has improved or has got worse. They will assess the person’s mental state and degree of memory loss. They will also use their judgement and any information carers can provide about how they are managing. They will repeat these tests every six months. When they think the medicine is no longer helping, they will stop prescribing it.


Medicines for later stage Alzheimer’s

There is another medicine available for moderate-to-severe Alzheimer’s, called memantine (Ebixa). It doesn’t help with early Alzheimer’s so isn’t usually prescribed until later in the course of the disease.

Memantine is a type of drug called an NMDA inhibitor. It works by helping to block signals from a ‘chemical messenger’ called glutamate, which can be overactive in Alzheimer’s. It can be particularly helpful with behavioural issues, such as agitation, irritability and aggression. It can have side-effects, including headache, constipation and dizziness.

Memantine is a tablet that you take once a day. The doctor is most likely to prescribe it on its own, but the person may have it as well as one of the medicines for earlier stage Alzheimer’s.


Other medicines that may be used in Alzheimer’s

More than eight out of 10 people (80%) diagnosed with Alzheimer’s will have some sort of emotional distress or behavioural disturbance at some point, such as anxiety, agitation, aggression or depression. Doctors used to treat agitation and aggressive behaviour with drugs used in psychiatric care, called anti-psychotics. We have since found that the risk of serious side-effects with these drugs is much higher in older people. This means they’re now less likely to be used. Doctors are more likely to prescribe the existing dementia drugs listed above and suggest other non-drug therapies for calming, such as aromatherapy.

About half of those diagnosed with dementia will also have depression. In around two out of every 10 (20%) Alzheimer’s patients, depression is severe enough to need treating. The doctor may suggest a course of anti-depressants. It’s important not to overprescribe medicines in older people, so doctors should not do this lightly and ought to stop the tablets if they think they’re not helping.


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Related information

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    Image from Cornelius C, Trovato Salinaro A, Scuto M et al. Cellular stress response, sirtuins and UCP proteins in Alzheimer disease: role of vitagenes. Immun Ageing. 2013 Oct 17;10(1):41. Reproduced under Creative Commons licence.

  • Produced by Nick Ridgman, Lead Health Editor, Bupa UK Health Content Team, December 2016
    Expert reviewer, Professor Graham Stokes, psychologist and dementia specialist
    Next review due December 2019



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