Epidemiology of Alzheimer’s disease

Summary

A survey is given of population studies on the prevalence and incidence of late-life dementia in general, showing an overall prevalence rate of 5–6% for moderate and severe dementia at the age of 65 and over, and of Alzheimer’s and vascular dementia in particular. In the European countries about 60% of all cases of late-life dementia seem to belong to Alzheimer’s, about 20% to multi-infarct dementia. In Japan and the USSR the share of vascular dementia is obviously greater. Both diseases show an exponential increase of prevalence rates with age in all populations investigated, starting from 2–3% in the age group 65–70 and surmounting 30% beyond 90 years of age, MID and AD doubling about every 5 years. The incidence rates for late-life dementia also show an exponential increase from about 0.3% at the age of 60–69, tripling every ten years of life and reaching around 3–4% at the age of 80 and over. Thus the exponential increase in prevalence is primarily due to the exponential age-dependent increase in the true morbid risk. The sex distribution for both types of dementia is still under discussion. The epidemiological study of genetic and environmental risk factors indicates that up to now only Down’s syndrome and a family history of AD are major risk factors for attracting AD in late life.