Three-month stability of the CogState brief battery in healthy older adults, mild cognitive impairment, and Alzheimer's disease: results from the Australian Imaging, Biomarkers, and Lifestyle-rate of change substudy (AIBL-ROCS).

Large prospective studies of Alzheimer's disease (AD) have sought to understand the pathological evolution of AD and factors that may influence the rate of disease progression. Estimates of rates of cognitive change are available for 12 or 24 months, but not for shorter time frames (e.g., 3 or 6 months). Most clinical drug trials seeking to reduce or modify AD symptoms have been conducted over 12- or 24-week periods. As such, we aimed to characterize the performance of a group of healthy older adults, adults with amnestic mild cognitive impairment (aMCI), and adults with AD on the CogState battery of tests over short test-retest intervals. This study recruited 105 healthy older adults, 48 adults with aMCI, and 42 adults with AD from the Australian Imaging, Biomarkers, and Lifestyle study and administered the CogState battery monthly over 3 months. The CogState battery of tests showed high test-retest reliability and stability in all clinical groups when participants were assessed over 3 months. When considered at baseline, the CogState battery of tests was able to detect AD-related cognitive impairment. The data provide important estimates of the reliability, stability, and variability of each cognitive test in healthy older adults, adults with aMCI, and adults with AD. This may potentially be used to inform future estimates of cognitive change in clinical trials.

Short term stability of verbal memory impairment in mild cognitive impairment and Alzheimer's disease measured using the International Shopping List Test.

There is a need for culture neutral neuropsychological instruments. The International Shopping List Test (ISLT) is sensitive to memory impairment in Alzheimer's disease (AD) in different cultural groups, although its sensitivity to mild cognitive impairment (MCI) and ability to be given repeatedly at short retest intervals is unknown. Performance on the ISLT was compared between groups of healthy adults, MCI, and AD from the Australian Imaging Biomarkers and Lifestyle study of ageing. Subjects were assessed four times in three months. In each group, the ISLT performance measures had high test-retest reliability, and group means remained stable over time. There was no difference between groups on within-subject variability. These data suggest that in English-speaking samples, the ISLT is sensitive to MCI and can be given repeatedly in order to assess change in memory.