Early Detection of Dementia of the Alzheimer's Type: Examining the Use of Cognitive Tasks and Neuropsychological Tests for Chinese with Minimal Education

• Main Author: Chang, Jianfang
• Format: Dissertation
• Language: English
• Subjects: education, educational psychology; psychology, psychobiology; psychology, psychometrics
• ISBN: 9781267258847; 1267258845

Dementia of the Alzheimer's Type (DAT) has become a critical public health problem with enormous cost to the society and patients' families. Early detection procedure that is sensitive and easily administrated is needed to discriminate DAT from normal aging so as to help to slow down the progress of their disease. In China, early identification of dementia is also of equal paramount importance given its over 100 millions age 60 years and older population and at least 5% of whom (totally 6 to 7 millions) are suffering from dementia.
The present thesis aimed to identify sensitive cognitive tasks and neuropsychological tests that could discriminate very mild DAT from normal aging among Chinese older adults with little formal education. The thesis compromises one major study (Study One) and supplementary studies (Studies Two and Three).
Study One examined whether the adapted attention tasks (face-number switching task, number Stroop switching task) and working memory tasks (counting span task, and digit suppression task) could discriminate people with very mild DAT from normal aging adults. A total of 139 participants (40 very mild DAT adults, 48 normal aging adults, and 51 young adults) were administrated Clinical Dementia Rating scale (CDR; Morris, 1993; Morris, McKeel, Fulling, Torack, & Berg, 1988) to stage the dementia status and employed aforementioned cognitive tasks as measurement of attention abilities. Intraindividual variability analyses and ex-Gaussian distribution analyses were used to capture the characteristics of RT performance for individuals in all three groups. The results showed that the pure trials in face-number switching task and digit suppression task performed as the most discriminating tasks. In comparison, the mixed block in the face-number switch task, the number Stroop switch task and the Counting Span task were comparatively less discriminating. Furthermore, the most discriminating indicators were residualized intraindividual standard deviation of RT performance and the tau value in ex-Gaussian distribution analyses in discriminating very mild DAT from normal aging.
Study Two examined the neuropsychological tests currently used in Hong Kong and tried to identify tests or subtests that would not work or even disadvantage (bias) Chinese illiterates or people with less education. As most traditional tests in screening dementia patients have been constructed in developed countries where 77.4% of older adults finished their high-school education, it is crucial that these tests are carefully scrutinized before their adoption for the Chinese population, where only about 16% and 20% did so in Hong Kong and in mainland China. Other than CDR, various neuropsychological tests were used to assess participants' cognitive functions: the Chinese Mini-Mental State Examination, the Chinese version of ADAS-Cog, the abstract thinking task, digit and visual span tests, and the Verbal Fluency Test. The purpose was to identify instruments that might not be suitable for Chinese with little or no education. Tests and subtests that are suitable for Chinese with little or no education, for those with more education and for both have been identified respectively.
Study Three tried to tease out potential pathways through which education protect people from dementia. Using the CMMSE subscales as indicators of different dimensions of performance, the study showed that education has a stronger protective effect on memory, orientation and judgment, and possibly through enhancing specific skills such as orientation of time and location and counting or recite downward (i.e., C-MMSE1, C-MMSE2, C-MMSE4).
Clinical implications and limitations of the results in various studies were discussed.