[Prospective study on the influence of social activity on development of dementia in the neurologically normal...

We investigated the rate of development of dementia in 84 neurologically normal elderly subjects living in an old-age home (30 subjects, mean 77.2 years) or their own home 954, 73.7) prospectively. We examined cerebral blood flow (CBF), Hasegawa's scale (HS) and Kohs' block design test 6 to 9 years before this study (1991). HS and Kohs' IQ were significantly lower in the old-age home group than that in their own home group at that time. However, there were no demented subjects. Mortality was 21%, and we confirmed 9 dementia and 6 stroke cases during the period of observation. Twenty-seven percent of the old-age home group showed dementia in 1991. This rate was significantly higher than that for the elderly living in their own home (6.7%). Occurrence of stroke was also significantly higher in the former group than in the latter group. The subjects who developed stroke during observation showed a high incidence of dementia. Mean CBF measured on the first examination was significantly lower in dementia cases with stroke than in dementia cases without it. We performed MRI in 4 demented cases in 1991 (Fig. 1). Two cases showed no significant lesions and the other cases showed cerebral infarction which could cause dementia. These results indicate that life style and social environment may have significant effect on aging of the brain and on development of dementia in the elderly.