Background:The aim of the present study was to estimate prevalence rates of dementia and its subtypes in the population aged 65 years or more in a rural area of Japan. Methods:A survey was conducted in Itoigawa, a city with 33 120 inhabitants in Niigata Prefecture, Japan. There were 7847 persons aged 65 years or older, and they comprised 23.4% of the total population. The first phase survey included questions on medical history, activities of daily living, psychiatric and behavioral symptoms and MMSE. When the responses were examined 6394 valid replies were received (81.5%) and 914 subjects were identified who were suspected of having dementia. In addition, 200 samples were selected randomly as controls from the 5480 people who were not suspected of dementia. The second phase survey was applied to a total of 1114 subjects. Pairs of psychiatrists and nurses made house-to-house visits and examined the subjects in detail. Clinical diagnoses of the subtypes of dementia were based on the criteria set out by the Consortium to Establish a Registry for Alzheimer's Disease and DSM IV. Results:The prevalence rate of dementia was estimated at 6.2% (men 4.5%, women 7.4%), which is higher than that found by previous reports in Japan. Alzheimer type dementia was the most frequent diagnosis, accounting for 4.0%, followed by vascular dementia (1.2%), other type of dementia (0.3%) and unknown dementia (0.8%). 'Questionable dementia', as defined by the Clinical Dementia Rating 0.5, was found in 4.4% of respondents (men 6.3%, women 3.0%). Conclusions:The prevalence of dementia in a rural area was higher than that of previous Japanese reports, and the prevalence rate of Alzheimer type dementia was much higher than that of vascular dementia.

Aim:The aim of this study was to develop a simple diagnostic procedure for subjects at high risk of developing dementia using the Clinical Dementia Rating (CDR), which is applicable to community-based activities.Methods: This study divided 252 communitydwelling elderly with a CDR score of 0.5 into two groups based on the presence or absence of cognitive decline within the previous one year of the baseline, as assessed by a semi-structured interview. One hundred subjects were in the 'previously progressive group' (PP group) and 152 subjects were in the 'previously stable group' (PS group). After 6 years of observation, a total of 111 subjects were assessed in the follow-up investigation.Results: Among the 39 subjects from the PP group (82.9 Ϯ 6.8 years old, 11 male, 28 female), 34 developed dementia (87%). Among the 72 subjects from the PS group (84.4 Ϯ 6.0 years old, 22 male, 50 female), 44 developed dementia (61%). The relative risk of developing dementia for the PP group versus the PS group was 1.43. The rate of conversion to dementia was 12.9% per 100 person-years in the PP group, and 9.8% in the PS group. In the PP group, the Mini-Mental State Examination score was significantly lower and the CDR score was significantly higher than in the PS group. Conclusion:Although there have been many attempts to identify subjects with high risk of dementia, this preliminary study suggests that information about temporal changes in cognitive function is useful when performing community-based surveys.

Background. A new public long-term care (LTC) insurance was launched in 2000 in Japan. However, there have been few studies involving factors that increase LTC costs of demented subjects; no follow-up studies involving the Government-Certified Index (GCI) and requisite costs related to the causes of dementia. Method. An epidemiological survey was conducted in a rural area in Japan in 1999, and 271 subjects were diagnosed as dementia patients. Age, sex, mini-mental state examination, clinical dementia rating, activity of daily living, causes of dementia, and coexisting physical disease were confirmed. After the LTC insurance has been launched, we tracked the GCI stages and payment amounts every month for 8 years. Result. 209 subjects were certified to be eligible for LTC insurance; however, 13 did not receive any payment. Only 49 out of 209 were alive after the follow-up period. The most common cause of dementia was Alzheimer's disease (AD), followed by vascular dementia (VaD). There was no significant difference between the mortality rates of the two groups. VaD subjects required higher costs than AD subjects in the total certified period and in GCI stage 5. Conclusion. Our results indicate that causes of dementia can have an impact on the requisite costs for the LTC insurance.