A Neuropathological Study of Dementia in Nursing Homes over a 17-Year Period, in Shimane Prefecture, Japan

Abstract

BACKGROUND: In Japan, vascular dementia (VD) has been responsible for the majority of all dementia cases in both epidemiological and neuropathological studies. Recently, however, several epidemiological investigations have shown that the rate of VD has decreased and senile dementia of the Alzheimer type (SDAT) is now the major cause of dementia, though few neuropathological investigations show that the majority of dementia is SDAT. OBJECTIVE: The purpose of the study was to clarify the rates of dementia types in Japanese nursing home residents and to compare the ratio of SDAT to VD in the first and second halves of the study. METHODS: One hundred and twenty-two demented nursing home residents (48 men and 74 women) were evaluated neuropathologically over a period of 17 years in Shimane prefecture, Japan. All subjects died between 1976 and 1992. The average age at death was 81.4 +/- 9.4 years for men, 85.0 +/- 7.2 for women and 83.6 +/- 8.3 for total samples. RESULTS: In classifying dementia type, SDAT accounted for 34% (41 cases); VD 35% (42); mixed dementia 11% (14); and 'other' dementia 20% (25) of all samples. Comparison of the first 9-year period with the second 8-year period revealed the ratio of SDAT to VD tended to increase (from 0.83 to 1.15). This increasing tendency was found both in men (from 0.53 to 0.7) and in women (from 1.13 to 1.44). These tendencies, however, were not statistically significant. CONCLUSION: There was no change statistically in the ratio of SDAT to VD between the first half of the study and the second half. However, there was an increasing tendency of the ratio in our study.