Quantifying longitudinal cognitive resilience to Alzheimer's disease and other neuropathologies

Abstract

Introduction Cognitive resilience (CR) has been defined as the continuum of better (or worse) than expected cognition, given the degree of neuropathology. To quantify this concept, existing approaches focus on either cognitive level at a single time point or slopes of cognitive decline. Methods In a prospective study of 1215 participants, we created a continuous measure of CR defined as the mean of differences between estimated person‐specific and marginal cognitive levels over time, after accounting for neuropathologies. Results Neuroticism and depressive symptoms were associated with all CR measures (P‐values < .012); as expected, cognitive activity and education were only associated with the cognitive‐level approaches (P‐values < .0002). However, compared with the existing CR measures focusing on a single measure or slopes of cognition, our new measure yielded stronger relations with risk factors. Discussion Defining CR based on the longitudinal differences between person‐specific and marginal cognitive levels is a novel and complementary way to quantify CR.

The association of MIND diet with cognitive resilience to neuropathologies

“…We examined two continuous measures of CR recently developed by our group and published in detail elsewhere. 18 These two measures are calculated using longitudinal data on global cognition, and nine measures of post mortem neuropathology. 18 Briefly, we focused on a composite score of global cognition based on 17 psychometric tests administered annually until death.…”

“…18 These two measures are calculated using longitudinal data on global cognition, and nine measures of post mortem neuropathology. 18 Briefly, we focused on a composite score of global cognition based on 17 psychometric tests administered annually until death. 19 Raw test scores were converted into z-scores, using the baseline mean and standard deviation (SD); at each assessment, the z-scores were averaged together, with higher scores indicating better function.…”

“…Our second CR measure focused on slopes of cognitive decline rather than levels of cognition, such that CR Slope was defined as the estimated residual slope of cognitive change, given a specific profile of neuropathologies. These two versions (see Wagner et al 18 for more details) capture different dimensions of CR; in particular, CR Level is strongly related to baseline cognitive level, and thus may reflect the accumulation of cognitive resources through the participant's life, whereas CR Slope focuses on residual cognitive change during follow-up, likely reflecting more immediate resilience to neuropathology.…”

“…17 Here, we extend this work by examining not only the MIND diet but also its dietary components, and by considering two complementary measures of cognitive resilience which separately examine: (1) consistently higher levels of cognition as well as (2) a slower rate of cognitive decline over time. 18 We leveraged dietary assessments, longitudinal cognitive assessments, and post mortem neuropathology from older, deceased participants with autopsies in the MAP cohort.…”