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[Prevalence of dementia and its subtypes in a rural area in Japan]
1Department of Neurology, Kyoto Prefectural University of Medicine, Japan.
Abstract:
The prevalence of dementia in Japan in 1985 for people aged 65 years or older was 4.8%. Vascular dementia (VD) has been reported to be the commonest subtype A report from Tokyo in 1970 showed that it was 2.8 times more frequent than Alzheimer type dementia (SDAT). We assessed the prevalence of dementia in a rural area (population: 12,931, 25.3% were 65 years or older in 1994) in Kyoko. First, we questioned subjects about their demographic circumstances, memory disturbance, apraxia (agnosia) and daily activities. Our questionnaire was answered by 3.132 (95.8%) subjects, and 2,280 of them agreed to be examined by neurologists. Those who met the appropriate criteria of the DSM-III-R and NINCDS-ADRDA were diagnosed with dementia. By use of the Hachinski ischemic score (HIS), we distinguished VD from non-vascular dementia. In this study patients with non-vascular dementia were diagnosed with SDAT by the neurologists. Analysis of the data revealed that 4.8% of the study population was demented. According to the HIS results, only 3 of 15 had vascular dementia. The prevalence of dementia was the same as the average prevalence in Japan even though the elderly population of this town was twice as high as the average. It is hard to determine the prevalence of dementia in any community. Many factors must be taken into consideration: the coverage rate, the criteria for dementia, and whether to include institutionalized residents. The prevalence of dementia will increase with the aging of the population, and we must collect accurate data in order to plan efficiently.
Insights
The prevalence of dementia in a rural Japanese community was 4.8%, matching the national average. This study highlights the challenges in accurately assessing dementia prevalence, especially in aging populations.
Area of Science:
- Epidemiology
- Gerontology
- Neurology
Context:
- Dementia prevalence in Japan was 4.8% in 1985 for those 65+.
- Vascular dementia (VD) is a common subtype, previously reported as 2.8 times more frequent than Alzheimer's type dementia (SDAT).
- Assessing dementia prevalence is complex, influenced by coverage rates, diagnostic criteria, and inclusion of institutionalized individuals.
Purpose:
- To assess the prevalence of dementia in a rural Japanese community.
- To distinguish between vascular dementia and non-vascular dementia (diagnosed as SDAT) using the Hachinski Ischemic Score (HIS).
- To compare the local prevalence with national averages and discuss factors influencing prevalence rates.
Summary:
- A study in a rural Kyoko area (12,931 population, 25.3% aged 65+) assessed dementia prevalence using questionnaires and neurological examinations.
- The study diagnosed dementia based on DSM-III-R and NINCDS-ADRDA criteria, differentiating VD using HIS.
- The overall dementia prevalence was 4.8%, with only 3 out of 15 dementia cases identified as VD. This prevalence matched the national average despite a higher elderly population.
Impact:
- The study found a dementia prevalence of 4.8% in the rural Japanese community, consistent with national figures.
- It underscores the difficulty in determining community dementia prevalence due to various methodological factors.
- Accurate data collection is crucial for efficient planning as dementia prevalence is expected to rise with an aging population.