We confirmed the overall prevalence of dementia in adults 65 years and older to be 8.5%. We found that VaD was not a common disorder according to the NINDS-AIREN criteria. Rather, the condition of possible Alzheimer disease with cerebrovascular disease was more common.

Background:The purpose of this study was to investigate the ability of normal elderly participants and patients with Alzheimer's disease to copy the Necker cube. Method: One hundred and seventy elderly participants were randomly selected from the town of Tajiri, northern Japan, and were classified into three groups based on the Clinical Dementia Rating (CDR): CDR 0, healthy; CDR 0.5, questionable dementia; and CDR 1 and 2, mild and moderate dementia. Dementia patients (CDR 1 and 2) met the criteria of probable AD of the NINCDS-ADRDA. Using eight original criteria, we examined their ability to copy the Necker cube. Results: Most CDR 0 participants could at least succeed in copying a simple cube. About a half of the AD patients could not draw a threedimensional figure. Among the CDR 0.5 participants, we found a 'two-peak' distribution. Conclusion: Copying the Necker cube may be one useful task for the detection of very mild Alzheimer's disease.

We examined the relations between cognitive function and age and education in the normal elderly population. As per the community-based stroke, dementia, and bed confinement prevention in the town of Tajiri, neuropsychological assessments, including the Cognitive Ability Screening Instrument (CASI), were performed for 99 randomly selected normal elderly subjects.We assessed the frontal function (working memory, word fluency, Trail-Making Tests, CASI subitems of list-generating fluency, attention, and concentration/mental manipulation), language function (proverbs, CASI subitem language), non-language function (the digit symbol test of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), CASI subitem visual construction), memory (Alzheimer's Disease Assessment Scale recall/recognition, story recall, CASI subitems short and long-term memory, the Rey-Osterrieth Complex Figure Test), and the global function (CASI subitems orientation and abstraction and judgment). We found that the only test affected by age was the digit symbol test of the WAIS-R. The effects of education were distributed among various tests. There was a significant correlation between age and the frontal lobe atrophy in the lower educated group. The present findings suggest that cognitive function is spared by the aging process itself and dementia should be considered as age-related, not aging-related disorders, and that education might have a protective effect on cognitive change, supporting the reserve hypothesis.

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