Cognitive test norms and comparison between healthy ageing, mild cognitive impairment, and dementia: A population-based study of older Aboriginal Australians

Abstract

Objective: The prevalence of dementia and cognitive impairment is higher in Aboriginal Australians compared to the national population, increasing the need to understand cognitive impairment in this at-risk population. This article reports normative data for a range of commonly used cognitive tests, in a population-based small normative sample of older Aboriginal Australians living in urban/regional New South Wales. Method: Participants included a representative random sample of community-dwelling older adults (60 years and older) with no cognitive impairment (n= 31),mild cognitive impairment (MCI;n= 38), or dementia diagnosis (n= 35), all from the Koori Growing Old Well Study. Cognitive tests included the Adden-brooke's Cognitive Examination Revised (ACE-R), Digit Span (Forward and Back-ward), Logical Memory, and the Oral Trail Making Test (A and B). Results: Descriptive statistics and percentile scores for each test were reported for the normative sample. Comparison of performance between the diagnostic groups showed significant differences between the groups on most cognitive tests. The control group consistently performed better than the dementia group; and better than the MCI group on all tests, except for simple attention and sequencing tasks (Digit Span Forward and Oral Trail Making A). The MCI group also scored better than the dementia group on all tests, except for the Logical Memory Recognition task. Conclusion: Results support the utility of these cognitive tests that are commonly used in clinical and research settings, and demonstrate that these tests can discriminate between diagnostic groups in Aboriginal Australians. The normative data provided will enhance cognitive assessment of individuals within this population.