A 6-Year Follow-up of Cognitive Function in a Rural Elderly Population / 신경정신의학

OBJECTIVES: This study was conducted to delineate the long-term natural change of cognitive functions in aged community residents, using the Korean version of the mini-mental state examination (MMSEK) METHODS: The first MMSEK was administered to as the screening test for identification of dementia between January and December, 1990 in a total of 702 persons. They were residents of a Myun area, Pohang, Kyungpook Province and 65 or more as of December 31. 1990. The MMSEK was repeated from November, 1995 to June, 1996, using the Cognitive Impairment Diagnosing Instrument and was successful in 440. RESULTS: The 6-year mean(+/-SD) decline of the total MMSEK score was 1.52+/-3.45 and 6.42%. Of the subtests, memory registration showed no significant decline while comprehension/judgement improved significantly. The decline was most prominent in attention/calculation and memory recall, and then language, orientation in time and orientation in place in order. Change of the total score was not related to sex, education and the first total score. Decline of language function was more severe in the educated than in the noneducated-illiterate. Performances of all subtests declined significantly with aging and improvement of the comprehension/judgement was less prominent in the group aged 75 or more. Relations of the change with the first total score were inconsistent among the subtests. The stepwise multiple regression analysis revealed that age, the first total score and education were the variables significantly affecting the decline of MMSEK score. However, they could account for only 16.4% of the variance of decline of the total MMSEK score. CONCLUSIONS:Decline of the cognitive function was small during the 6-year period, and the change pattern was not homogenous among the subtests. Age, the first total MMSEK score and education were idenrified as significant, but not so important, factors accounting for the variance of the cognitive decline.

Diagnostic Predictive Values of Cognitive Function Tests

OBJECTIVE: The positive and negative predictive values are more important as the diagnostic validity than the sensitivity and specificity in the general population with a low prevalence rate of a disease. The present study is about the diagnostic predictive values of the Korean version of mini-mental state examination and Cognitive Impairment Diagnosing Instrument in an unselected community elderly group. METHOD: The positive and negative diagnostic values were calculated based on the Bayes theorem, using the sensitivity and specificity of the Korean version of mini-mental state examination and Cognitive Impairment Diagnosing Instrument and a previously reported prevalence rate. RESULTS: When the prevalence of dementia is 10.8% among elderly people living in a community, the positive predictive value, negative predictive value and combined error were estimated as being 56.7%, 99.0%, and 8.4%, respectively, at cutoff score of 23 of the Korean version of mini-mental state examination for diagnosing dementia. In the case of the Cognitive Impairment Diagnosing Instrument, they were 64.2%, 99.1% and 6.3%, respectively, at the point of 57 or less in an unselected community sample with the same prevalence. If the sensitivity and specificity are constant, the positive predictive values of the Korean version of mini-mental state examination and Cognitive Impairment Diagnosing Instrument incresed markedly with the rising prevalence while the negative predictive values and combined errors changed little. CONCLUSION: If a variety of diagnostic tests available are similar in the diagnostic sensitivity and specificity, a test with higher positive predictive value should be prefered because the negative predictive value and combined error are not significantly influenced by the prevalence. In this regard, the Cognitive Impairment Diagnosing Instrument may be superior to the Korean version of mini-mental state examination.

Diagnostic Predictive Values of Cognitive Function Tests

OBJECTIVE: The positive and negative predictive values are more important as the diagnostic validity than the sensitivity and specificity in the general population with a low prevalence rate of a disease. The present study is about the diagnostic predictive values of the Korean version of mini-mental state examination and Cognitive Impairment Diagnosing Instrument in an unselected community elderly group. METHOD: The positive and negative diagnostic values were calculated based on the Bayes theorem, using the sensitivity and specificity of the Korean version of mini-mental state examination and Cognitive Impairment Diagnosing Instrument and a previously reported prevalence rate. RESULTS: When the prevalence of dementia is 10.8% among elderly people living in a community, the positive predictive value, negative predictive value and combined error were estimated as being 56.7%, 99.0%, and 8.4%, respectively, at cutoff score of 23 of the Korean version of mini-mental state examination for diagnosing dementia. In the case of the Cognitive Impairment Diagnosing Instrument, they were 64.2%, 99.1% and 6.3%, respectively, at the point of 57 or less in an unselected community sample with the same prevalence. If the sensitivity and specificity are constant, the positive predictive values of the Korean version of mini-mental state examination and Cognitive Impairment Diagnosing Instrument incresed markedly with the rising prevalence while the negative predictive values and combined errors changed little. CONCLUSION: If a variety of diagnostic tests available are similar in the diagnostic sensitivity and specificity, a test with higher positive predictive value should be prefered because the negative predictive value and combined error are not significantly influenced by the prevalence. In this regard, the Cognitive Impairment Diagnosing Instrument may be superior to the Korean version of mini-mental state examination.