Mental aging and its medico-psycho-social background in the very old Japanese.

By clinical observations of 115 centenarians and 742 nonagenarians, the actual state of mental aging of the very old Japanese and some factors relating to it are shown in this paper. A great difference in psychophysical functions was found between the centenarians and the nonagenarians. Most centenarians manifested a distinct decline in these functions, while a decline was less prominent in the 90-year-olds. There was a significant relationship between mental and physical functions. Those manifesting a prominent decline in intellectual ability showed more frequent reduction in physical ability as well, and vice versa. The degree of their intellectual ability was also related to the following factors: their sex, academic and occupational careers, some types of personality traits and personality changes. The mental decline was less prominent in males, in the educated and in those with a syntonic personality than in others.