Abstract
In the present study, we investigated differences in amyloid (Aβ) burden and personality traits in cognitively-select older adults compared to average-functioning older adults. Conscientiousness, in particular, has been linked to Alzheimer's Disease (AD) pathology, and we hypothesized that adults who were high in cognition would exhibit enhanced conscientiousness. Of additional interest was whether high functioning older adults in the Dallas Lifespan Brain Study would evidence reduced AD pathology. We tested 285 cognitively-normal participants (ages 55-90) and collected conscientiousness scores using the Revised NEO Personality Inventory (NEO-PI-R). Participants also underwent PET imaging with radiotracer AV-45, 18F-Florbetapir, a radiotracer that is used to measure Aβ protein in the brain. Mean cortical SUVR was computed across 8 cortical regions of interest, normalized to cerebellar gray matter. In addition, participants completed a cognitive battery, underwent an MRI scan, and completed self-reports for depression and fitness. We designated those participants scoring at or above the mean episodic memory of a middle-aged (ages 35-54) reference group, as "cognitively-select" (N = 69), and those scoring below the mean, as "cognitively-normal" (N = 216). Dependent variables of interest included global and regional amyloid (Aβ), cortical morphometry, depression, fitness, conscientiousness, and various cognitive measures. Cognitively select participants were younger (p = .043), more educated (p = .021), and had higher positive personality traits, including self-discipline (p = .01), openness to ideas (p = .013), and competence (p = .015), compared to cognitively-normal. Although the groups did not differ in global Aβ pathology load (p = .083), cognitively select exhibited less pathology in specific regions including lateral temporal areas (p = .049). Regression analysis controlling for sex, age, education, and MMSE, revealed a significant group by global Aβ interaction on fluid ability (p = .034), where greater Aβ load predicted lower scores in cognitively normal older adults only. These findings provide evidence that cognitively privileged adults show resistance to decline across many domains and demonstrate resilience to amyloid pathology. Discussion will focus on longitudinal change in amyloid accumulation, cortical thinning, and cognitive decline, as well as the concept of reserve.
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