Subtype analysis of neuropathologically diagnosed patients in a Japanese geriatric hospital☆
Introduction
Dementia research over the last decade has uncovered a complex assortment of clinical and pathological manifestations. In Japan, vascular dementia (VD) and Alzheimer-type dementia (ATD) have been considered to be the two main causes of dementia in the aged. Previous comprehensive statistical studies of Japanese cases showed greater numbers of VD patients than ATD patients [1]. However, recent epidemiological studies in Japan have indicated that the incidence of ATD is slightly higher than that of VD [2]. In addition, until we demonstrated that diffuse Lewy body disease (DLBD) was a distinct disease entity, it was generally misdiagnosed as ATD or Parkinson's disease (PD) with dementia [3]. In Western countries, neurodegeneration associated with ATD probably accounts for 50–60% of elderly dementia patients, and VD is considered to be in no more than 8–10% of the dementia case [4].
In order to improve diagnostic reliability and validity, operational criteria have been developed for these pathologic disorders and for the clinical syndromes associated with them (e.g. NINCDS-ADRDA and NINDA-AIREN) [5], [6]. These concepts have shaped the clinical nosology of dementia as currently described in DSM-IV and ICD 10, but these systems do not incorporate recent findings regarding dementia with Lewy bodies (DLB) which may, in fact, affect a substantial proportion of elderly patients with dementia. We have attempted to correct this oversight by reporting on DLB [3], [7], [8], [9], [10], [11], [12]. Recently, consensus guidelines for clinical and pathological diagnosis of DLB were established [13], [14]. However, our interest in DLB began years earlier when we first began neuropathological examination of elderly patients with dementia. In our study, we investigated 239 autopsied cases over a 10-year period after obtaining the consent of family members. The number of cases examined comprised only 16.9% of the total number (1418) of deceased patients. In fact, the autopsy ratio was not high, but we believe that there was no skewing of our findings since autopsies were performed only on obtaining family agreement, and therefore would represent a form of random sampling. The data obtained would reflect true tendencies in the Japanese population at large with respect to elderly patients with neurological and/or psychiatric problems.
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Patients
All 239 cases examined in our follow-up study were patients who had died while hospitalized. They had undergone neuropsychological tests that consisted of the Mini-Mental State Examination (MMSE) [15] and the assessment by Hasegawa's dementia scale (HDS) [16] or the HDS revised version (HDS-R) [17] which is a neuropsychological test widely utilized in Japan. We also recorded interviews employing comprehensive questions concerning psychological and medical symptoms, chronic conditions,
Summary of main dementia group
A total of 239 patients were examined. Male (103) and female (136) patients with an average age of 81.9±8.56 (mean±SD) at death were analyzed over 10 years. Of these, 66% (158 cases) had experienced dementia symptoms and were diagnosed with dementia. Details of each dementia group are described in Table 1a. Classification of non-Alzheimer degenerative dementias was carried out according to a previous report [22].
Following examination of data of dementia patients collected over the past decade
Discussion
There have been only a few reports in Japan of long-term studies (over 10 years) of large groups (over 200 patients) of neuropathologically investigated cases. Although VD was thought to be the most frequent type of dementia affecting elderly Japanese [1], ATD has recently been shown to be the predominant dementia [2]. However, as seen in Table 1b, although there were some differences after 1990, the relative proportion of ATD showed no tendency to increase on a year-to-year basis (data not
Acknowledgements
We thank the patients and their guardians for cooperating with our project. We also thank the medical staff and attending physicians, Dr. Katsuaki Funabashi, Dr. Toshihide Ikuno, Dr. Hideki Nakahata, Dr. Sayuri Tani, Dr. Tomoaki Ikeda, Dr. Katsuhiko Tanabe, Dr. Katsunada Fujimoto, Dr. Hiroaki Hino, Dr. Kazumasa Shiozaki, Dr. Tomomi Katoh, Dr. Tsunemichi Matsubara, Dr. Akira Tomita, Dr. Yasuko Sugita, Dr. Tetsuo Kawawaki, Dr. Tsuyoshi Yamaguchi, Dr. Jyouji Fukuyama, Dr. Hiroyuki Ikari, Dr. Kouji
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This work was discussed and approved by the ethical committee of Fukushimura Hospital, June 2nd, 2000, and assigned application number 39.