Alzheimer’s disease is the most common type of dementia, affecting almost 50,000,000 people in the worldwide.

The term “dementia” describes a loss of mental ability associated with gradual death of brain cells.

The exact cause of Alzheimer’s disease is unknown, although a number of things are thought to increase your risk of developing the condition. These include:

  • increasing age
  • a family history of the condition
  • previous severe head injuries
  • lifestyle factors and conditions associated with cardiovascular disease

Symptoms of Alzheimer’s disease

The symptoms of Alzheimer’s disease progress slowly over several years. They are often similar to those of other conditions and may initially be put down to old age.

The rate at which the symptoms progress differs for each individual and it is not possible to predict exactly how quickly it will get worse.

In some cases, infections or medications can be responsible for the worsening of symptoms. Anyone with Alzheimer’s disease whose symptoms are rapidly getting worse should be seen by a doctor so these causes can be ruled out.

Stages of Alzheimer’s disease

Generally, the symptoms of Alzheimer’s disease are divided into three main stages.

Early symptoms

In the early stages, the main symptom of Alzheimer’s disease is memory lapses. For example, someone with early Alzheimer’s disease may:

  • forget about recent conversations or events
  • forget the names of places and objects
  • repeat themselves regularly, such as asking the same question several times
  • show poor judgement or find it harder to make decisions
  • become unwilling to try out new things or adapt to change

There may also be some early signs of mood changes, such as increasing anxiety or agitation, or periods of confusion.

Middle stage symptoms

As Alzheimer’s disease develops, memory problems will get worse and someone with the condition may find it increasingly difficult to remember the names of people they know and may struggle to recognise their family and friends.

Other symptoms may also develop, such as:

  • increasing confusion and disorientation – for example, not knowing where they are and walking off and getting lost
  • obsessive, repetitive or impulsive behaviour
  • delusions (believing things that are untrue)
  • problems with speech or language (aphasia)
  • disturbed sleep
  • changes in mood, such as frequent mood swings, depression and feeling increasingly anxious, frustrated or agitated
  • difficulty performing spatial tasks, such as judging distances
  • problems with eyesight, such as poor vision or hallucinations (seeing things that are not there)

By this stage, someone with Alzheimer’s disease will usually need support to help them with their everyday living. For example, they may need help eating, washing, getting dressed and using the toilet.

Later symptoms

In the later stages of Alzheimer’s disease, the symptoms become increasingly severe and distressing for the person with the condition, as well as their carers, friends and family.

Hallucinations and delusions will often become worse and the person with the condition may start to become violent, demanding and suspicious of those around them.

A number of other symptoms may also develop as Alzheimer’s disease progresses, such as:

  • difficulty eating and swallowing (dysphagia)
  • difficulty changing position or moving around without assistance
  • considerable weight loss (although some people eat too much and put on weight)
  • unintentional passing of urine (urinary incontinence) or stools (bowel incontinence)
  • gradual loss of speech
  • significant problems with short- and long-term memory

During the severe stage of Alzheimer’s disease, people often start to neglect their personal hygiene. It is at this stage that most people with the condition will need to have full-time care because they will be able to do very little on their own.

Causes of Alzheimer’s disease

Alzheimer’s disease is caused by parts of the brain wasting away (atrophy), which damages the structure of the brain and how it works.

It is not known exactly what causes this process to begin, although people with Alzheimer’s disease have been found to have abnormal amounts of protein (amyloid plaques), fibres (tau tangles) and a chemical called acetylcholine in the brain.

These reduce the effectiveness of healthy neurons (nerve cells that carry messages to and from the brain), gradually destroying them.

Over time, this damage spreads to several areas of the brain, such as the grey matter (responsible for processing thoughts) and the hippocampus (responsible for memory).

Increased risk

Although it is still unknown what triggers Alzheimer’s disease, several factors are known to increase your risk of developing the condition.


Age is the single most significant factor in the development of Alzheimer’s disease. The likelihood of developing the condition doubles every five years after you reach 65 years of age.

However, it is not just older people who are at risk of developing Alzheimer’s disease. Around 1 in 20 people with the condition are under 65. This is called early-onset Alzheimer’s disease and it can affect people from around 40 years of age.

Family history

The genes you inherit from your parents can contribute to your risk of developing Alzheimer’s disease, although the actual increase in risk is small if you have a close family member with the condition.

However, in a few families, Alzheimer’s disease is caused by the inheritance of a single gene, and the risks of the condition being passed on are much higher.

If several of your family members have developed dementia over the generations, it may be appropriate to seek genetic counselling for information and advice about your chances of developing Alzheimer’s disease when you are older.

The Alzheimer’s Society website has more information about genetics and dementia.

Down’s syndrome

People with Down’s syndrome are at a higher risk of developing Alzheimer’s disease.

This is because the genetic fault that causes Down’s syndrome can also cause amyloid plaques to build up in the brain over time, which can lead to Alzheimer’s disease in some people.

Whiplash and head injuries

People who have had a severe head injury or severe whiplash (a neck injury caused by a sudden movement of the head) have been found to be at higher risk of developing Alzheimer’s disease.

Cardiovascular disease

Research shows that several lifestyle factors and conditions associated with cardiovascular disease can increase the risk of Alzheimer’s disease.

These include:

  • smoking
  • obesity
  • diabetes
  • high blood pressure
  • high cholesterol

You can help reduce your risk by stopping smoking if you smoke, eating a healthy, balanced diet, and having regular health checks as you get older. It is also important to keep as active as possible, both mentally and physically, to help reduce the risk of Alzheimer’s disease

Diagnosing Alzheimer’s disease

See your Doctor if you are worried about your memory or think you may have dementia.

If you’re worried about someone else, you should encourage them to make an appointment and perhaps suggest that you go along with them.

An early diagnosis gives you the best chance to prepare and plan for the future, as well as receive any treatment that may help.

Seeing your Doctor

Memory problems are not just caused by dementia – they can also be caused by depression, stress, medications or other health problems. Read about common causes of memory loss.

Your Doctor will be able to carry out some simple checks to try to find out what the cause may be. They can refer you to a specialist for further tests if necessary.

Your Doctor will ask about your symptoms and other aspects of your health, and will carry out a physical examination. They may also organise some blood tests and ask about any medication you are taking to rule out other possible causes of your symptoms.

You may also be asked some questions or be asked to carry out some simple activities to assess any problems with your memory or your ability to think clearly. This can help your Doctor decide if you need to be referred to a specialist for further assessment.

Referral to a specialist

Your Doctor may refer you to a specialist to help with your diagnosis. For example, you may be referred to:

  • a clinical psychologist – a healthcare professional who specializes in the assessment and treatment of mental health conditions
  • a psychiatrist – a qualified medical doctor who has further training in treating mental health conditions
  • a neurologist – a specialist in treating conditions that affect the nervous system (the brain and spinal cord)

The specialist may be based in a memory clinic alongside other professionals who are experts in diagnosing, caring for and advising people with dementia and their families.

There is no simple and reliable test for diagnosing Alzheimer’s disease, but your specialist can help assess your memory and thinking skills, and arrange further tests to rule out other conditions.

Assessing your mental abilities

A specialist will usually assess your mental abilities using a special questionnaire.

One widely used test is the mini mental state examination (MMSE). This involves being asked to carry out activities such as memorizing a short list of objects correctly and identifying the current day of the week, month and year.

The MMSE is not used to diagnose Alzheimer’s disease, but it is useful for assessing the level of mental impairment that a person with the condition may have. This helps specialists make decisions about treatment and whether further tests are necessary.


To rule out other possible causes of your symptoms and look for possible signs of damage caused by Alzheimer’s disease, your specialist may recommend having a brain scan. This could be a:

  • computerized tomography (CT) scan – where several X-rays of your brain are taken at slightly different angles and a computer is used to put the images together
  • magnetic resonance imaging (MRI) scan – where a strong magnetic field and radio waves are used to produce detailed images of the inside of your brain

After diagnosis

It may take several appointments and tests over months, or even years, before a diagnosis of Alzheimer’s disease can be confirmed.

For some people, a diagnosis of Alzheimer’s disease is a huge shock, whereas for others it simply confirms what had been suspected for a long time.

If you’ve just had a diagnosis of dementia, you’re probably feeling numb, scared and unable to take everything in, so give yourself a little time to adjust. It might help to talk things through with family and friends.

Once the initial feelings have passed, it’s important to think about moving forward and creating an action plan for the future. Dementia is a progressive illness, so the sooner you take care of legal, financial and healthcare matters, the better.

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