[Oldest-old dementia in a Japanese memory clinic]

To elucidate the characteristics of oldest-old patients with dementia in a Japanese memory clinic.

We evaluated 365 consecutive patients with dementia who were referred to the Memory Clinic of Niigata Rehabilitation Hospital, Niigata, Japan over 4-year period. More than 85% of the patients lived in the communities within 15 km from the hospital. The mean (+/- SD) age at examination was 79.3 +/- 6.9 years, and according to this criterion the patients were classified into 4 groups: young (age less than 65 years), younger-old (65-74 years), older-old (75-84 years), oldest-old (85 years or more). In each patient group, we evaluated the rates of the major dementias and compared the demographic and clinical characteristics of the patients with Alzheimer's disease (AD).

The rates of major dementias in all the patients was as follows: AD, 74.5%; dementia with Lewy bodies (DLB), 13.7%; frontotemporal lobar degeneration (FTLD), 3.0%; vascular dementia (VD), 5.5%, and other dementias, 3.3%. The number of patients included in the young group was 9; in the younger-old group, 75; in the older-old group, 203; and in the oldest-old group, 78. The rates of major dementias in each old group was as follows: in the younger-old group, 74.7% for AD, 9.3% for DLB, 6.7% for FTLD, 5.3% for VD and 4.0% for other dementias; in the older-old group, 73.4% for AD, 15.8% for DLB, 1.5% for FTLD, 5.9% for VD, and 3.5% for other dementias; and in the oldest-old group, 78.2% for AD, 14.1% for DLB, 2.6% for FTLD, 3.9% for VD and 1.3% for other dementia. The AD patients in the oldest-old group showed a significantly higher rate of female (younger-old, 64.3%; older-old, 79.2%; and oldest-old, 85.3%; chi2 = 7.9, p < .05), a poorest mean of the score on the Alzheimer's Disease Assessment Scale (younger-old, 18.5 +/- 10.4; older-old, 19.2 +/- 9.3; and oldest-old, 22.8 +/- 7.6; F = 3.5, p < .05), and a poorest distribution on the Clinical Dementia Rating (chi2 = 13.9, p < .05).

The rates of the major dementias were similar in the younger-, older-, and oldest-old groups except for the higher rate of FTLD and the lower rate of DLB, respectively, in the younger-old patients. The cognitive and overall dementia severity status of the oldest-old patients with AD referred to the memory clinic was poor than that of the younger- and older-old patients.