identify prevalence rates for different types of dementia
Dementia is estimated1 to afflict over 35.5 million people worldwide - this includes nearly 10 million people in Europe, nearly 4.4 million in North America, nearly 7 million in South and Southeast Asia, [ about 5.5 million in China and East Asia and about 3 million in Latin America.
The estimated prevalence for over 60s is 4.7% worldwide. Because this is a disorder of age, prevalence is of
course greatly affected by the proportion of people reaching their senior years. Hence the prevalence is higher in the more developed countries: the estimated prevalence in Western Europe and North America is 7.2% and 6.9% respectively, compared to 2.6% in Africa.
What kinds of dementia are most common?
The prevalence of the various dementia types is a complicated story. Certainly Alzheimer's disease is by far the most common type of dementia, accounting for perhaps 70% of all dementias (although a 2006 study13 suggested that non-Alzheimer dementias were as common as Alzheimer's — however this was based on dementia among military veterans). The second most common dementia is almost certainly vascular dementia, which may account for some 17% of dementias. However, the actual numbers are made uncertain by the fact that these two dementias often occur together.
At minimum, around a quarter of Alzheimer's cases have been found, on autopsy, to also have vascular pathology; this proportion reaches higher levels when the samples are not restricted to dementia clinics. One such community-based study2, for example, found 45% of the Alzheimer's cases also showed significant vascular pathology. Another, U.K., study3 found a similar proportion (46%). ]
There are no new answers.