Dementia in the Aged

Abstract

Vascular dementia (VD) and Alzheimer-type dementia (ATD) are two main causes of dementia in the aged, accounting for more than 90% of cases with dementia. VD has been reported to be more frequent than ATD in Japan, but recent epidemiological studies in Gunma prefecture and other locations reveal the incidence of ATD becoming slightly higher than that of VD. This reversal of VD/ATD incidence ratio is suggestd to be due to decrease of the incidence of VD based on the recent development of treatment of cerebrovascular disease. With regard to ATD, various approaches to clarify its etiology are now in progress mainly invloving research on the mechanism of formation of neurofibrillary tangles and senile plaques which characterize the pathology of ATD. Studies on hereditary types of ATD suggest that the etiologies of ATD are heterogeneous, but the deposition of β-protein followed by τ-protein with resulting dementia seems to be the common process of ATD. Some biological diagnostic markers are now being examined to evaluate their use in early diagnosis. On the other hand, VD occurs mainly due to cerebral infarction, and can be classified due to the responsible lesions. Our study with positron emission tomography reveals that most cases with VD show decrease of the cerebral metabolic ratio in bilateral frontal lobes. VD is clinically characterized by its temporal profile and neurological findings. VD may becoming a type of preventable, treatable dementia.