Aim: To describe fundamental cognitive function and change in the elderly and examine interaction between cognition and ADL.
Methods: We investigated the mental and physical condition of 12,140 persons aged 65 years or over in 2000 and 2002 according to the Eligibility Survey Questionnaire for Long-term Care Insurance. The percentage correct and correlation coefficients of six items in the Questionnaire concerning "Understanding" : "Understands daily activities", "Answers date of birth and age", "Remembers what the subject did before interview", "Says own name", "Knows what season it is now", "Knows the place where the subject is" were determined. The interaction between these six items and ADL were also examined.
Results: The percentage correct of "name" was .89, "date of birth and age" .78, "place" .75, "season" .66, "daily activities" .59, "Remembers before interview" .58. The item with high percentages of correct answer in 2000 higher tended to remain high in 2002. Those who were not impaired physically but unable to understand cognitive items tended to require significantly more support for ADL such as "Dressing and undressing", and "Personal hygiene", "Taking medication".
Conclusion: The percentage correct of each item was considered to be associated with a classical model of memory process: encoding, retention and retrieval. It seemed to require the whole memory process to "Understand daily activities" and "Remember before interview", since the contents were changeable. On the other hand, "name" and "date of birth and age" were relatively well preserved, since these items were encoded and stored in the early stage of life and retrieved repeatedly. "Place" and "Season" were between these two groups.