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Who's at risk and why?

Adults :: Dementia :: Who's at risk and why?

Dementia is a clinical syndrome characterised by a widespread loss of mental function, including memory loss, language impairment, disorientation, change in personality, self-neglect and behaviour which is out of character. [1]

Risk factors

The most important risk factor is age. Other risk factors are learning disabilities, socio-economic status and alcohol.

Age and sex

The table below shows estimated prevalence rates from the most recent consensus exercise [2] broken down by age group. Most dementia is late onset (affecting people aged 65 and over) with about 1 in 40 cases being early onset (up to the age of 64 years).

  Female rate per
100,000 population
Male rate per
100,000 population
30-34 9.5 8.9
35-39 9.3 6.3
40-44 19.6 8.1
45-49 27.3 31.8
50-54 55.1 62.7
55-59 97.1 179.5
60-64 118.0 198.9
Table 1: Prevalence of early onset dementia in the UK by age and gender [2]
  Female percent Male percent
65-69 1.0 1.5
70-74 2.4 3.1
75-79 6.5 5.1
80-84 13.3 10.2
85-89 22.2 16.7
90-94 29.6 27.7
95+ 34.4 30.0
Table 2: Prevalence of late onset dementia in the UK by age and gender [2]

Tables 1 and 2 highlight the importance of age as the key risk factor for dementia. 1–1.5% of 65–69 year olds are likely to have dementia compared with 30–35% of adults over 95. The prevalence of dementia increases significantly with age. A higher proportion of females experience dementia than males.

Learning disabilities

Early onset dementia can be linked to learning disabilities and there is a suggestion of increasing levels of alcohol related dementia. Not only can people with learning disabilities have an increased risk of developing dementia but the early stages of the condition can be missed or misinterpreted. As people with learning disabilities are living longer there is an increasing need for awareness and early detection of the condition. A study of people with Down's syndrome found the following prevalence of Alzheimer's disease: [3]
• 30–39 years: 1 in 50
• 40–49 years: 1 in 10
• 50–59 years: 1 in 3
• 60–69 years: more than half

Studies have also shown that in later life almost all people with Down’s syndrome develop the changes in the brain associated with Alzheimer's disease, although not all develop the symptoms of Alzheimer's.

Studies suggest the numbers of people with learning disabilities other than Down's syndrome who have dementia are approximately: [3]


• 50–65 years: 1 in 10
• 65–75 years: 1 in 7
• 75–85 years: 1 in 4
• 85+ years: nearly three-quarters

These numbers indicate a risk about three to four times higher than in the general population.

Socio-economic status

The rate of cognitive problems has been found to be higher in people of lower social class and lower educational achievement. [4]

Alcohol

This is important particularly with respect to Korsakoff's dementia which is reported to affect 12.5% of dependent drinkers.

Types of dementia

There are a number of types of dementia which are caused by different diseases of the brain. These different types of dementia are associated with different risk factors.

The most common type is Alzheimer's disease, affecting about 62% of those with dementia. Vascular dementia (17%), including multi-infarct dementia and Lewy Body dementia, are the next most common forms as well as mixed presentations. About 10% of people with dementia have both Alzheimer's disease and vascular dementia.

  Proportion of people
with dementia
Alzheimer’s disease 62
Vascular dementia 17
Mixed (AD and VD) 10
Dementia with Lewy bodies 4
Frontotemporal dementia 2
Parkinson’s dementia 2
Other 3
Table 3: Types of dementia [2]
Alzheimer's

A physical disease affecting the brain leading to the death of brain cells. It is a progressive disease that becomes more severe over time. It is characterised by confusion and memory loss, mood swings, social withdrawal and poor social functioning.

The primary risk factor is age. There is some evidence of genetic factors and also smoking and hypotension have been linked to increased risk of getting Alzheimer's.

People with Downs Syndrome have increased risk of getting Alzheimer's due to chromosomal abnormalities

Vascular Dementia

Certain factors can increase a person's risk of developing vascular dementia. These include:
• a medical history of stroke, high blood pressure, high cholesterol, diabetes (particularly type II), heart problems, or sleep apnoea (where breathing stops during sleep)
• a lack of physical activity, drinking more than recommended levels of alcohol, smoking, eating a fatty diet, or leaving conditions such as high blood pressure or diabetes untreated
• a family history of stroke or vascular dementia
• gender - men are slightly more likely to develop vascular dementia
• an Indian, Bangladeshi, Pakistani, Sri Lankan or African Caribbean ethnic background

Mixed dementia — Alzheimer's and Vascular

It is estimated that this form of dementia consists of 10% of the total number of people diagnosed with a dementia. Dementia with Lewy Bodies (DLB) and Parkinson's Disease Dementia (PDD) If symptoms of dementia are noted with a year of the person being diagnosed with Parkinson's, a diagnosis of DLB will be made. This is caused by tiny spherical protein deposits that develop inside nerve cells in the brain. These interrupt the brains normal functioning affecting the person's memory, concentration and language skills. If the symptoms appear over a year after the Parkinson's diagnosis, a diagnosis of PDD will be given.

Korsakoff's / Alcohol-related dementia

Those affected tend to be men between the ages of 45 and 65 with a long history of alcohol abuse. Although numbers affected by Korsakoff's are small (component of 'other' forms of dementia which make up 3% total cases), it is reported to affect 12.5% of dependent drinkers and has implications for health and social care services as it affects a younger age group where dementia support is targeted at older people.

Other dementias

Included in this are Fronto-Temporal Dementia (2% of total) along with less common types such as CJD.


References

[1]   Department of Health. National Framework for Older People 2001;
[2]   Emiliano DA, Banerjee PS, Dhanasiri S, et al. Dementia UK: The Full Report 2007; Alzheimer's Society. http://alzheimers.org.uk/site/scripts/download.php?fileID=2 .
[3]   Alzheimer's Society. Factsheet: Learning disabilities and dementia 2011;
[4]   Ott A, Breteler M, van Harskamp F, et al. Prevalence of Alzheimer's disease and vascular dementia: association with education, the Rotterdam study British Medical Journal 1995; 310: 970-3.