The word ‘dementia’ describes a set of symptoms that may include memory loss and difficulties with thinking, problem-solving or language. These changes are often small to start with, but for someone with dementia they have become severe enough to affect daily life. A person with dementia may also experience changes in their mood or behaviour.

Dementia is caused when the brain is damaged by diseases, such as Alzheimer’s disease or a series of strokes. Alzheimer’s disease is the most common cause of dementia, but not the only one. The specific symptoms that someone with dementia experiences will depend on the parts of the brain that are damaged and the disease that is causing the dementia.

Symptoms

Each person is unique and will experience dementia in their own way. The different types of dementia also tend to affect people differently, especially in the early stages. Other factors that will affect how well someone can live with dementia include how other people respond to them and the environment around them.

A person with dementia will have cognitive symptoms (to do with thinking or memory). They will often have problems with some of the following:

• day-to-day memory – for example, difficulty recalling events that happened recently
• concentrating, planning or organising – for example, difficulties making decisions, solving problems or carrying out a sequence of tasks (such as cooking a meal)
• language – for example, difficulties following a conversation or finding the right word for something
• visuospatial skills – for example, problems judging distances (such as on stairs) and seeing objects in three dimensions
• orientation – for example, losing track of the day or date, or becoming confused about where they are.

A person with dementia will also often have changes in their mood. For example, they may become frustrated or irritable, apathetic or withdrawn, anxious, easily upset or unusually sad. With some types of dementia, the person may see things that are not really there (visual hallucinations) or strongly believe things that are not true (delusions).

Dementia is progressive, which means the symptoms gradually get worse over time. How quickly this happens varies greatly from person to person. As dementia progresses, the person may develop behaviours that seem unusual or out of character. These behaviours may include asking the same question over and over, pacing, restlessness or agitation. They can be distressing or challenging for the person and those close to them.

A person with dementia, especially in the later stages, may have physical symptoms such as muscle weakness or weight loss. Changes in sleep pattern and appetite are also common.

Causes

There are many diseases that result in dementia. The most common types of dementia are outlined below:

Alzheimer’s disease – This is the most common cause of dementia. In Alzheimer’s disease, an abnormal protein surrounds brain cells and another protein damages their internal structure. In time, chemical connections between brain cells are lost and cells begin to die. Problems with day-to-day memory are often the first thing to be noticed, but other symptoms may include difficulties finding the right words, solving problems, making decisions, or perceiving things in three dimensions.

Vascular dementia – If the oxygen supply to the brain is reduced because of narrowing or blockage of blood vessels, some brain cells become damaged or die. This is what happens in vascular dementia. The symptoms can occur suddenly, following one large stroke. Or they can develop over time, because of a series of small strokes. Vascular dementia can also be caused by disease affecting the small blood vessels deep in the brain, known as subcortical vascular dementia. The symptoms of vascular dementia vary and may overlap with those of Alzheimer’s disease. Many people have difficulties with problem-solving or planning, thinking quickly and concentrating. They may also have short periods when they get very confused.

Mixed dementia – This is when someone has more than one type of dementia, and a mixture of the symptoms of those types. It is common for someone to have both Alzheimer’s disease and vascular dementia together.

Dementia with Lewy bodies – This type of dementia involves tiny abnormal structures (Lewy bodies) forming inside brain cells. They disrupt the chemistry of the brain and lead to the death of brain cells. Early symptoms can include alertness that varies over the course of the day, hallucinations, and difficulties judging distances. A person’s day-to-day memory is usually affected less than in the early stages of Alzheimer’s disease. Dementia with Lewy bodies is closely related to Parkinson’s disease and often has some of the same symptoms, including difficulty with movement.

Frontotemporal dementia (including Pick’s disease) – In frontotemporal dementia, the front and side parts of the brain are damaged. Clumps of abnormal proteins form inside brain cells, causing them to die. At first, changes in personality and behaviour may be the most obvious signs. Depending on which areas of the brain are damaged, the person may have difficulties with fluent speech or forget the meaning of words.

The symptoms of these types of dementia are often different in the early stages but become more similar in the later stages. This is because more of the brain is damaged as the different diseases progress. In the later stages of dementia, the person will need more and more support to carry out everyday tasks. However, many people with dementia live well for years after their diagnosis.

Rarer Causes of Dementia

There are many other diseases that can lead to dementia. These are rare – together they account for only about 5 per cent of all dementia. They tend to be more common among younger people with dementia (under the age of 65). These rarer causes include corticobasal degeneration, progressive supranuclear palsy, HIV infection, Niemann-Pick disease type C, and Creutzfeldt-Jakob disease (CJD).

Some people with Parkinson’s disease or Huntington’s disease develop dementia as the illness gets worse. People with Down’s syndrome are also at a particular risk of developing Alzheimer’s disease as they get older.

Mild Cognitive Impairment

Some people have problems with their memory or thinking but these are not bad enough to affect their everyday life. In this case, a doctor may diagnose them with mild cognitive impairment (MCI). This is not a type of dementia, but research shows that people with MCI have an increased risk of going on to develop dementia.

Diagnosis of Dementia

It is very important for anyone who has problems with their memory or thinking to get a proper assessment. These problems may be caused by a treatable condition such as depression or an infection, rather than dementia. Finding out the cause may allow the person to get the right treatment.

If these problems are because of dementia, getting a diagnosis has many benefits. It provides someone with an explanation for their symptoms, gives them access to treatment, advice and support, and allows them to prepare for the future and plan ahead. Knowing the type of dementia (for example, Alzheimer’s disease or vascular dementia) is also important, partly because it may allow the person to get an appropriate drug treatment.

There is no single test for dementia. A diagnosis is based on a combination of things:

• taking a ‘history’ – the doctor talking to the person and someone who knows them well about how their problems developed and how they are now affecting their daily life
• physical examination and tests (for example, blood tests) to exclude other possible causes of the person’s symptoms
• tests of mental abilities (for example, memory, thinking) – simpler tests will be carried out by a nurse or doctor, more specialist tests by a psychologist
• a scan of the brain, if this is needed to make the diagnosis.