EURODEM - the European Community Concerted Action on the Epidemiology and Prevention of Dementia Group - calculated these prevalence rates based solely on diagnosed cases of AD (Hofman et al 1991). This makes an accurate estimate of the number of people with dementia difficult because:

- Many people with dementia never receive an AD diagnosis.

- Estimate excludes those in the early stages of dementia who have yet to be diagnosed.

Prevalence rates increase from ~2% in the 65 - 69 year old population to ~22% of those aged 85-89.