What is Dementia?
are caused by disorders affecting the brain. It is not
one specific disease.
Dementia affects thinking, behaviour and the ability to
perform everyday tasks. Brain function is affected
enough to interfere with the person's normal social or
working life. The hallmark of dementia is the inability
to carry out everyday activities as a consequence of
diminished cognitive ability.
Doctors diagnose dementia if two or more cognitive
functions are significantly impaired. The cognitive
functions affected can include memory, language
skills, understanding information, spatial skills,
judgement and attention. People with dementia
may have difficulty solving problems and controlling
their emotions. They may also experience
The exact symptoms experienced by a person with
dementia depend on the areas of the brain that are
damaged by the disease causing the dementia. The
condition is usually progressive; the disease
gradually spreads through the brain and the
person's symptoms get worse over time.
Who gets dementia?
Dementia can happen to anybody, but the risk
increases with age. Most people with dementia are
older, but it is important to remember that most older
people do not get dementia. It is not a normal part of
ageing, but is caused by brain disease. Less
commonly, people under the age of 65 years develop
dementia and this is called 'younger onset dementia'.
There are a few very rare forms of inherited
dementia, where a specific gene mutation is known
to cause the disease. In most cases of dementia
however, these genes are not involved, but people
with a family history of dementia do have an
Certain health and lifestyle factors also appear to play
a role in a person's risk of dementia. People with
untreated vascular risk factors including high blood
pressure, cholesterol and diabetes have an increased
risk, as do those who are less physically and mentally
What causes dementia?
There are many different diseases that cause
dementia. In many cases, why people develop these
diseases is unknown. Some of the most common
forms of dementia are:
Alzheimer's disease is the most common form of
dementia, accounting for around two-thirds of cases.
It causes a gradual decline in cognitive abilities, often
beginning with memory loss.
Alzheimer's disease is characterised by two
abnormalities in the brain – amyloid plaques and
neurofibrillary tangles. The plaques are abnormal
clumps of a protein called beta amyloid. The tangles
are bundles of twisted filaments made up of a protein
called tau. Plaques and tangles stop communication
between nerve cells and cause them to die.
Vascular dementia is cognitive impairment caused by
damage to the blood vessels in the brain. It can be
caused by a single stroke, or by several strokes
occurring over time.
Vascular dementia is diagnosed when there is
evidence of blood vessel disease in the brain and
impaired cognitive function that interferes with daily
living. The symptoms of vascular dementia can begin
suddenly after a stroke, or may begin gradually as
blood vessel disease worsens. The symptoms vary
depending on the location and size of brain damage.
It may affect just one or a few specific cognitive
functions. Vascular dementia may appear similar to
Alzheimer's disease, and a mixture of Alzheimer's
disease and vascular dementia is fairly common.
Lewy body disease
Lewy body disease is characterised by the presence
of Lewy bodies in the brain. Lewy bodies are
abnormal clumps of the protein that develop inside
nerve cells. These abnormalities occur in specific
areas of the brain, causing changes in movement,
thinking and behaviour. People with
Lewy body disease may experience large fluctuations
in attention and thinking. They can go from
almost normal performance to severe confusion
within short periods. Visual hallucinations are also a
Three overlapping disorders can be included with
Lewy body disease:
• Dementia with Lewy bodies
• Parkinson's disease
• Parkinson's disease dementia
When movement symptoms appear first, Parkinson's
disease is diagnosed. As Parkinson's disease
progresses most people develop dementia. When
cognitive symptoms appear first, this is diagnosed as
dementia with Lewy bodies.
Lewy body disease sometimes co-occurs with
Alzheimer's disease and/or vascular dementia.
Frontotemporal dementia involves progressive
damage to the frontal and/or temporal lobes of the
brain. Symptoms often begin when people are in
their 50s or 60s and sometimes earlier. There are
two main presentations of frontotemporal dementia
– frontal (involving behavioural symptoms and
personality changes) and temporal (involving
language impairments). However, the two often
Because the frontal lobes of the brain control
judgement and social behaviour, people with
frontotemporal dementia often have problems
maintaining socially appropriate behaviour. They may
be rude, neglect normal responsibilities, be
compulsive or repetitive, be aggressive, show a lack
of inhibition or act impulsively.
There are two main forms of the temporal or
language variant of frontotemporal dementia.
Semantic dementia involves a gradual loss of the
meaning of words, problems finding words and
remembering people's names, and difficulties
understanding language. Progressive non-fluent
aphasia is less common and affects the ability to
Frontotemporal dementia is sometimes called
frontotemporal lobar degeneration (FTLD) or Pick's
There are a number of conditions that produce
symptoms similar to dementia. These can often be
treated. They include some vitamin and hormone
deficiencies, depression, medication effects,
infections and brain tumours.
It is essential that a medical diagnosis is obtained at
an early stage when symptoms first appear to ensure
that a person who has a treatable condition is
diagnosed and treated correctly. If the symptoms are
caused by dementia, an early diagnosis will mean
early access to support, information and medication
should it be available.
What are the early signs of dementia?
The early signs of dementia can be very subtle, vague
and may not be immediately obvious. Some common
symptoms may include:
• Progressive and frequent memory loss
• Personality change
• Apathy and withdrawal
• Loss of ability to perform everyday tasks What can be done to help?
At present there is no cure for most forms of
dementia. Some medications have been found to
reduce some symptoms and other therapies can
reduce the rate of progression. The person
diagnosed with dementia can also make plans for
their future and their family can come to
understand what is happening. Support is vital for
people with dementia and the help of families, friends
and carers can make a positive difference to
managing the condition.