Cross-national comparisons of the occurrence of Alzheimer's and vascular dementias.

The relative occurrence of Alzheimer's and vascular dementias is examined in various countries using data of four types: incidence, prevalence, clinic and neuropathological studies. There is clear evidence that Alzheimer's dementia is more common than vascular dementia in Great Britain and North America and, to a lesser extent, in Scandinavia. The evidence from other countries with predominantly Caucasian populations is more limited, but also supports a predominance of Alzheimer's dementia. By contrast, the evidence from Japan generally shows that vascular dementia is more common. The more limited evidence available from China also supports a preponderance of vascular dementia. There is a need for studies directly comparing the occurrence of Alzheimer's dementia in Caucasian and Oriental populations.