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.

The Trail Making Test (TMT) is a common two-part neuropsychological test, in which visuospatial ability (TMT-A) and executive function (TMT-B) are evaluated. Normative data for this test have not been reported for Japanese subjects; therefore, the purpose of the present paper was to investigate the effect of age and education on the TMT in 155 healthy elderly adults with clinical dementia rating 0 (healthy). The participants were classified into three groups based on age (70-74 years, 75-84 years and ≥85 years), and also into three groups based on educational level (6 years, 8 years and ≥10 years). The time to complete TMT-A and TMT-B were measured, and the difference in score between TMT-A and TMT-B (B-A) and the ratio of the score (B/A) were calculated as indices of executive function. The time for completion of both parts of the TMT increased markedly in the ≥85-years group. For TMT-A, there was a significant difference between the 6-years and 8-years groups, and between the 6-years and ≥10-years groups, and for TMT-B, there was a significant difference between the 6-years and ≥10-years groups, and between the 8-years and ≥10-years groups. The difference and ratio scores increased in the ≥85-years group, but the educational level did not significantly influence these scores. Our data suggest that cognitive functions evaluated by TMT-A and TMT-B are not affected by aging until the subjects are ≥85 years old. For TMT-A, an educational effect becomes apparent when the population includes poorly educated subjects, but this part of the test is not affected by educational level provided that the subjects have some education (>6 years). The time to complete TMT-B is affected by educational level, consistent with previous reports. However, when adjusted using the results for TMT-A [(B-A) or (B/A)], the educational effect on executive function disappeared. Thus, the effect of educational level on executive function was unclear in normal elderly subjects.

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The borderline zone condition between normal aging and dementia is a major issue of concern. Although the term mild cognitive impairment (MCI) is popular, its prevalence and neuropsychological features have not been fully investigated. We investigated the prevalence and neuropsychological features for Clinical Dementia Rating (CDR) 0.5 and MCI. For normal aging, the effects of age and educational level on cognitive performance were examined. We examined 1501 older residents (46.8%) in Tajiri 65 years of age and older. They performed the Cognitive Abilities Screening Instrument (CASI). Depressive scores and subjective memory complaints were also evaluated. There was no age effect but an educational effect on cognitive performance in healthy adults. We found the overall prevalence of CDR 0.5 to be 30.2%, whereas that of MCI was only 4.9%. All CASI domains were deteriorated except for long-term memory and visual construction in the CDR 0.5 participants compared with healthy adults, suggesting that CDR 0.5 is similar to very mild Alzheimer disease. Memory complaints' data suggested that it would be better to exclude memory complaints from the MCI criteria. We considered that the concept of CDR 0.5 would be more applicable to community residents rather than that of the MCI.

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