Genetic characteristics of dementia in Taiwan.

The most common causes of dementia in Taiwan are Alzheimer's disease (AD) followed by vascular dementia (VaD). Several genetic studies have documented an increased risk of AD among apolipoprotein E gene allele 4 (ApoE4) carriers in Taiwanese (ethnic Chinese). Although ApoE4 is considered the most important risk factor for AD, the ApoE4 allele frequency is lower in Taiwanese (around 7%), than that in most Caucasian populations (over 10%). This phenomenon raises the hypothesis that low ApoE4 allele frequency contributes to the low prevalence of AD in Taiwanese. Other studies of the genetic impacts on modulation or regulation of manifestations, progression, and treatment response of AD in Taiwan have been inconclusive. Familial AD, which is conferred by PS1 gene mutation has been identified. There were very few studies of fronto-temporal dementia (FTD) or dementia with Lewy body (DLB) in Taiwan. Genetic studies of VaD remain limited and only NOTCH3 gene mutation has been detected in a Taiwanese cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL) family. Limited data indicated that non- ApoE4-associated AD may represent a larger proportion of AD in Taiwanese, suggesting the existence of novel genetic factors which remain to be identified.