Graduate Theses and Dissertations (2019 - present)

Date of Award

8-2025

Document Type

Dissertation

Degree Name

Ph.D.

Department

Clinical and Counseling Psychology

Committee Chair

Benjamin D. Hill

Abstract

Alzheimer’s disease (AD) is a progressive and irreversible neurocognitive disorder. Several genetic and non-genetic factors have been identified as contributors to the etiology of AD, including biomarkers, the presence of specific genotypes, and modifiable risk factors. Racial disparities in AD have been observed with Black and Hispanic populations displaying disproportionate rates of AD compared to non-Hispanic White populations. The evaluation of AD commonly incorporates Neuropsychological evaluation. Cognitive intra-individual variability (IIV) refers to within-person change in performance and has been found to be an indicator of cognitive functioning.

The first aim of this project evaluated cognitive IIV as a moderator of the relationship between neuropsychological functioning and neuropathology. A secondary aim was to examine differences in cognitive IIV by racial/ethnic groups and apolipoprotein ε (APOE) status. Lastly, this project explored the relationship between cognitive IIV and modifiable risk factors (i.e., physical activity, mood, stress). This study utilized archival data from a larger study, the Health and Aging Brain Study, Health Disparities (HABS-HD).

To address the primary aim, an exploratory factor analysis (EFA) was conducted utilizing biomarkers to create a factor of neuropathology. An additional EFA was conducted to create factors of cognitive functioning using neuropsychological assessment scores. Cognitive IIV was calculated using the standard deviation of the overall test battery mean of neuropsychological tests. A moderation analysis was conducted with IIV as the moderator between neuropathology and cognitive functioning. A multivariate analyses of covariance (MANCOVA) with race/ethnicity and APOE c4 status as the independent variables and cognitive IIV and neuropsychological test performance as the dependent variables while education was examined as a covariate. Lastly, to evaluate whether modifiable risk factors have any relationship with cognitive IIV, a stepwise multiple regression was conducted with modifiable risk factors entered as independent variables and cognitive IIV as the dependent variable.

The EFA of biomarkers produced a single factor of neuropathology and the EFA of neuropsychological measures produced a three-factor solution. Cognitive IIV was a significant predictor but was not found to moderate the relationship between neuropathology and cognitive performance. Results of the MANCOVA revealed education and race/ethnicity to be predictive of IIV but not APOE status. In the final aim, mood was the only modifiable risk factor which significantly predicted cognitive IIV.

Results of this study support cognitive IIV to be a significant predictor of cognitive functioning. Similar to general neuropsychological tests, cognitive IIV was impacted by demographic factors such as education and race/ethnicity as well as lifestyle factors such as mood.

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