What is dementia?

Ty Hapus carer and guestAlzheimer's disease is the most common cause of dementia, affecting around 465,000 people in the UK. The term 'dementia' describes a set of symptoms which can include loss of memory, mood changes, and problems with communication and reasoning. These symptoms occur when the brain is damaged by certain diseases and conditions, including Alzheimer's disease. This factsheet outlines the symptoms and risk factors for Alzheimer's disease, and describes what treatments are currently available.

Alzheimer's disease, first described by the German neurologist Alois Alzheimer, is a physical disease affecting the brain. During the course of the disease, protein 'plaques' and 'tangles' develop in the structure of the brain, leading to the death of brain cells. People with Alzheimer's also have a shortage of some important chemicals in their brain. These chemicals are involved with the transmission of messages within the brain.

Alzheimer's is a progressive disease, which means that gradually, over time, more parts of the brain are damaged. As this happens, the symptoms become more severe.


People in the early stages of Alzheimer's disease may experience lapses of memory and have problems finding the right words. As the disease progresses, they may:

  • become confused and frequently forget the names of people, places, appointments and recent events
  • experience mood swings, feel sad or angry, or scared and frustrated by their increasing memory loss
  • become more withdrawn, due either to a loss of confidence or to communication problems
  • have difficulty carrying out everyday activities - they may get muddled checking their change at the shops or become unsure how to work the TV remote.

As the disease progresses, people with Alzheimer's will need more support from those who care for them. Eventually, they will need help with all their daily activities.

While there are some common symptoms of Alzheimer's disease, it is important to remember that everyone is unique. No two people are likely to experience Alzheimer's disease in the same way.

Mild cognitive impairment

Recently, some doctors have begun to use the term mild cognitive impairment (MCI) when an individual has difficulty remembering things or thinking clearly but the symptoms are not severe enough to warrant a diagnosis of Alzheimer's disease. Recent research has shown that individuals with MCI have an increased risk of developing Alzheimer's disease. However, the conversion rate from MCI to Alzheimer's is low (about 10-20 per cent each year), and consequently a diagnosis of MCI does not always mean that the person will go on to develop Alzheimer's.

What causes Alzheimer's disease?

So far, no one single factor has been identified as a cause for Alzheimer's disease. It is likely that a combination of factors, including age, genetic inheritance, environmental factors, lifestyle and overall general health, are responsible. In some people, the disease may develop silently for many years before symptoms appear.


Welcome to Ty HapusAge is the greatest risk factor for dementia. Dementia affects one in 14 people over the age of 65 and one in six over the age of 80. However, dementia is not restricted to older people: in the UK, there are over 16,000 people under the age of 65 with dementia, although this figure is likely to be an underestimate.

Genetic inheritance

Many people fear that they may inherit Alzheimer's disease and scientists are currently investigating the genetic background to Alzheimer's.

We do know that there are a few families where there is a very clear inheritance of the disease from one generation to the next. This is often in families where the disease appears relatively early in life.

In the vast majority of cases, however, the influence of inherited genes for Alzheimer's disease in older people seems to be small. If a parent or other relative has Alzheimer's, your own chances of developing the disease are only a little higher than if there were no cases of Alzheimer's in the immediate family.

For more information see our factsheet on Genetics and dementia (405).

Environmental factors

The environmental factors that may contribute to the onset of Alzheimer's disease have yet to be identified. A few years ago, there were concerns that exposure to aluminium might cause Alzheimer's disease. However, these fears have largely been discounted.

Other factors

Because of the difference in their chromosomal make-up, people with Down's syndrome who live into their 50s and 60s are at particular risk of developing Alzheimer's disease.

People who have had severe head or whiplash injuries also appear to be at increased risk of developing dementia. Boxers who receive continual blows to the head are at risk too.

Research has also shown that people who smoke, and those who have high blood pressure, high cholesterol levels or diabetes, are at increased risk of developing Alzheimer's. You can help reduce your risk by not smoking, eating a healthy balanced diet and having regular checks for blood pressure and cholesterol from middle age. Maintaining a healthy weight and leading an active lifestyle combining physical, social and mental activity will also help.

Getting a diagnosis

If you are concerned about your own health, or the health of someone close to you, it is important to seek help from a GP. An early diagnosis will have a number of benefits including the opportunity to plan for the future and access treatment, advice and support.

There is no straightforward test for Alzheimer's disease or for any other cause of dementia. A diagnosis is usually made by excluding other causes which present similar symptoms. The GP will need to rule out conditions such as infections, vitamin deficiency, thyroid problems, depression and the side-effects of medication.


The GP may ask a specialist for help in carrying out a diagnosis. The specialist may be an old-age psychiatrist, a neurologist, a physician in geriatric medicine or a general psychiatrist. Who the person sees will depend on their age, how physically able they are and how well services are developed in the local area.

Younger people with dementia

There are more than 16,000 younger people with dementia in the UK. However, this number is likely to be an under-estimate, and the true figure may be up to three times higher. Data on the numbers of people with early onset dementia are based on referrals to services, but not all those with early onset dementia seek help in an early stage of the disease. The symptoms of dementia may be similar whatever a person's age, but younger people may have different needs, and their problems often require a different approach.

Types of dementia in younger people

'Younger people with dementia' is a term that includes anyone diagnosed with dementia under the age of 65. People also use the terms 'early onset dementia', 'young onset dementia', or 'working age dementia'.

Only around one-third of younger people with dementia have Alzheimer's disease.