L17 Chronic disease epidemiology - old age

Question 1

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Dementia and cognitive health

• Dementia affects 35 million people worldwide, new case ever 7 seconds
• In UK, cost >£21 billion
• Alzheimer’s disease responsible for 65% cases
• Vascular dementia 10-20% cases (some “mixed”)
• Dementia with Lewy bodies 10-15% cases in older people
• Fronto-temporal dementia 10-15% cases in younger people
• Other rare causes (Prion dementias)

Estimating the prevalence of dementia:

• Possible approaches using existing data
• Mortality statistics
• Hospital activity information
• Disability/carer benefits
• Examination of people known to medical services

Dementia subtype diagnosis:

• There are no definitive imaging or laboratory tests for the diagnosis of dementia subtypes
• The evaluation depends on careful history taking with a reliable informant
• Following by physical and cognitive examination
• And increasingly adding this to information from imaging and other biomarkers
• Ultimately diagnosis made at autopsy

Question 2

What is Mild Cognitive Impairment?

Answer 2

Transitional state between ‘normal’ ageing and pathological decline.

Question 3

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The continuum of cognitive impairment

• Most diseases can be classified as being present or not present in an individual
• A common method for analysis of risk factors is to compare cases vs controls.
• Cognitive impairment and dementia exist on a continuum.
• So selecting cases known to services (with dementia) and volunteer controls (without dementia) excluding those in which diagnosis is uncertain can lead to bias
• Particularly a problem in the oldest old population where controls are difficult to identify
• Over-estimate the effect of interventions in the population