Fat Chung and Trish (Patricia) Vella-Burrows

Key points

  • • Introduction
  • • Defining dementia
  • • Common types of dementia
  • • Rising rates of dementia
  • • The impact of dementia
  • • Risk factors for dementia
  • • Primary prevention of dementia
  • • Secondary prevention of dementia
  • • Tertiary prevention of dementia
  • • Summary


This chapter will explain why dementia is a public health priority for the world, with a focus on the UK. It will define dementia and describe four common types. It will present data to show the anticipated significant rise in the number of people living with dementia over the next few decades. The challenges of dementia for countries, families, carers and individuals are examined through a discussion about the costs of care, the impact on the wider economy and the personal impacts for individuals and those around them. The chapter describes the non-modifiable and modifiable risk factors for developing dementia. It concludes with an overview of the primary, secondary and tertiary prevention of dementia.

Defining dementia

Dementia is not a disease, but a cluster of symptoms that can include memory loss, psychiatric and psychological changes, disturbances in language and impairments in daily living (Burns and Illiffe, 2009). The World Health Organization defines dementia as a syndrome which is usually chronic or progressive in nature. There is a

... deterioration in cognitive function ... beyond what might be expected from normal ageing. It affects memory, thinking, orientation, comprehension, calculation, learning capacity, language, and judgement. Consciousness is not affected.

The impairment in cognitive function is commonly accompanied ... by deterioration in emotional control, social behaviour, or motivation.

(WHO, 2019a)

Dementia is caused by a variety of injuries or diseases that either directly or indirectly affect the brain, such as Alzheimer’s disease. It comprises signs and symptoms that range from mild, such as when forgetfulness starts to affect a person’s functioning, to the most severe, when the person becomes dependent on others to assist with most aspects of their daily living.

Mild cognitive impairment

Mild cognitive impairment means that an individual has problems with thinking or memory, but this alone does not lead to a diagnosis of dementia (NICE 2019). Between 5% and 20% of people aged over 65 in the UK have mild cognitive impairment. Of those, about half are likely to develop dementia (NICE, 2019; Alzheimer’s Society, 2020a).

Common types of dementia

There are about 200 types of dementia (Foley and Swanwick, 2014). Each is characterised according to the area and type of damage to the brain (WHO 2019a; NICE, 2019). Dementia that is diagnosed under the age of 65 is called ‘early-onset’ or ‘young-onset’ dementia. Here we describe Alzheimer’s disease, vascular dementia, dementia with Lewy bodies and frontotemporal dementia.

It is important to note that dementia is more complex than this medical model suggests. During the 1990s, post-mortem research with people who had been diagnosed with dementia showed that damage to brain tissue does not always correlate with the person’s behaviour or expression of cognition (Snowdon, 1997). Some people with moderate to severe brain tissue damage were higher functioning than expected and vice versa. The science of dementia is by no means the complete story, and today emphasis is placed on looking for social, psychological and other personal factors which provide a more holistic understanding of each individual person’s experience of dementia (Vella-Burrows, 2015).

Alzheimer’s disease

Alzheimer’s disease was named after the clinician Alois Alzheimer in 1906. It is the most common cause of dementia, accounting for 60% to 70% of all cases across the world and 50% to 75% of cases in the UK (WHO, 2019a; NICE, 2019). It is caused by [1]

Together, these cause brain cells to die (Alzheimer’s Society, 2020a; RCP, 2019).

Key features include

  • • memory loss, which is usually gradual and sometimes insidious
  • • difficulty in recalling recent events and learning new information
  • • progressive changes in personality and behaviour
  • (NICE 2019)

Whilst Alzheimer’s disease often affects older people, around 5% of cases in the UK and world-wide are under 65. Some people living with Alzheimer’s disease also experience symptoms and signs of vascular dementia or dementia with Lewy bodies. In these cases, a diagnosis of mixed dementia is given (ARUK, 2018a; NICE, 2019).

Vascular dementia

Vascular dementia makes up about 20% of all cases of dementia in the UK (NICE, 2019). It is caused when the blood fails to deliver enough oxygen to the brain cells, which then die (BHF, 2019; NICE, 2019). This can be due to a stroke or other damage to blood vessels.

Key features will vary according the location of damage in the brain. They include

  • • confusion
  • • difficulty in attention and speech
  • • memory loss
  • • gait/mobility problems
  • • changes in personality
  • (NICE, 2019)

Dementia with Lewy bodies

Dementia with Lewy bodies is the third most common type of dementia, accounting for 10% to 15% of all people living with dementia in the UK (ARUK, 2019). It is caused by

  • • abnormal deposits of protein inside the nerve cells in the brain. These are called Lewy bodies after Frederick Lewy who discovered them in 1912
  • • disruption to brain chemicals
  • • the loss of connections between nerve cells

Together, these cause brain cells to die (McKeith et al., 2017; Alzheimer’s Society, 2020a).

Key features will depend on the location of the Lewy bodies and include [2]

  • • rapid eye movement (REM) sleep behaviour disorder, which means someone may act out vivid dreams with sound and bodily movements
  • (Kane et al., 2018; McKeith et al., 2017; Outeiro et al., 2019)

Frontotemporal dementia

Frontotemporal dementia, formerly called Pick’s disease, occurs in around 2% of all dementia cases in the UK (NICE, 2019). About one-third have some family history of dementia (Alzheimer’s Society, 2020a). It is a significant cause of dementia in people aged under 65 and is the third most common cause of young-onset dementia. It is caused by an accumulation of tau proteins, called Pick bodies, in the brain which cause the gradual deterioration of the brain’s frontal and/or temporal lobes (NICE 2019). Key features include

  • • changes in personality and behaviour, such as poor judgement and foresight
  • • problems with understanding, speaking and writing
  • • problems with walking, balance and coordination
  • • problems with vision and mood
  • • muscle weakness and wasting
  • (Alzheimer’s Society, 2020a; Alzheimer’s Association, 2020)

There are about 200 types of dementia with different underlying causes and consequences for the lives of individuals.

  • [1] a build-up of amyloid plaques. These are types of proteins that clump togetherbetween the nerve cells in the brain • an increase in neurofibrillary tangles, twisted fibres, in the brain • a reduction of neurotransmitters, the chemicals that transmit messages betweenthe brain cells
  • [2] visual hallucinations • fluctuating levels of cognitive impairment • problems with movement, sometimes like the tremors or slow movementsassociated with Parkinson’s disease
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