Longitudinal Trajectories of Normal versus Abnormal Cognitive Aging in the SIU Longitudinal Cognitive Aging Study as measured by the original Alzheimer’s disease Assessment Scale and a novel extended version

Abstract

AbstractBackgroundThe original Alzheimer’s disease Assessment Scale‐cognitive subscale (oADAS) is a common measure of cognition used in Alzheimer’s disease (AD) clinical trials. The oADAS may not be sensitive to pre‐dementia syndromes such as mild cognitive impairment (MCI), possibly due to ceiling effects for many of the subtests. However, little is known about the trajectories of cognitive aging on the oADAS in cognitively‐normal individuals who decline over time. We used Linear Mixed Effects Modeling to examine trajectories of cognitive aging on the oADAS, a novel extended version (eADAS), and the MMSE. We hypothesized that, compared to non‐decliners, individuals who declined from normal to MCI and/or AD (decliners) would demonstrate increased error scores on the ADAS and lower scores on the MMSE over time.MethodsWe included data from 608 older adults (72% female, mean age = 69.0 years) who were enrolled in SIU Longitudinal Cognitive Aging Study (LCAS). Total years of educational attainment ranged from 8‐26 years. The vast majority of the participants were White/Not‐Hispanic. There were 50 decliners and 558 non‐decliners included in the present analysis. The eADAS included short‐delay recall/recognition trials for the first word list, a short‐delay true‐false word recognition trial for the second word list, a letter‐digit d psychomotor test, supermarket fluency, spontaneous clock drawing, three additional items to the object naming subtest, three additional figure copies, and a similarities test. All analyses were completed after controlling for gender, education, age at first visit, time between visits, and number of visits.ResultsThere was no significant difference between the groups for age at first visit. Greater age at first visit and lower education were associated with increased error scores for both ADAS versions and MMSE in the decliner group (p’s <0.001). There was no significant effect of the number of days between visits. The mean coefficients for the change in error score over time between visits for the oADAS, eADAS, and MMSE was 2.84, 10.30, and ‐1.09, respectively.ConclusionOur results indicate that the oADAS and eADAS are useful measures for examining trajectories of cognitive decline in cognitively‐normal individuals at increased risk for AD.