Dementia is commonly viewed as a health and social problem of older adults, however dementia may occur earlier in life. Young onset dementia is defined by an onset of symptoms before the age of 65 years. The most frequent underlying causes of YOD are diseases where nerve cells gradually become dysfunctional and die away (Alzheimer’s disease, Frontotemporal degenerations) or nerve cells are lost due to lack of blood supply as a consequence of small vessel occlusions (Cerebrovascular diseases).

The frequency of YOD is estimated at 100 per 100.000 in the population age between 45 and 65 years in Europe, Japan and the United States. The rate of new cases is 5-20 per 100.000 per year in this age group. There is a total of 16.000 affected individuals in France and United Kingdom and a total of 24.000 affected individuals in Germany. The number of new cases per year is 3.200 and 4.800 in these countries, respectively.