Cutter A. Lindbergh

The Relationship Between Cognitive Reserve and Functional Ability is Mediated by Executive Functioning in Older Adults

It has been noted in the literature that cognitive reserve (CR) predicts future functional ability (FA), but the association between CR and current FA is rather limited. This investigation aimed to explicate this relationship, and hypothesized it would be mediated by executive functioning (EF). To best understand the relationship between CR and FA, we recruited and tested independent community-dwelling older adults (OAs). Bivariate correlations and hierarchical regressions were completed to determine the association between CR and FA. Both individual CR measures and a composite CR score were used. Mediation analyses were completed to examine our hypothesis that EF would mediate the CR and FA relationship. All measures of CR were positively related to and predictive of FA. Although the highest zero-order correlation across the independent CR proxies was between income and FA (r = .417), education accounted for the greatest amount of variance in FA, 8.3% after controlling for age and Mini-Mental State Examination performance. Furthermore, the CR composite had a higher correlation (r = .447) and accounted for more variance than any of the independent proxies. Complete mediation was found between a CR composite and FA via an internally consistent D-KEFS composite score (Cronbach’s α = .795). This suggests that as CR increases so does EF, which in turn improves FA. Thus, future investigations could determine the effect on FA in OAs by improving EF.

Lutein and Zeaxanthin Influence Brain Function in Older Adults: A Randomized Controlled Trial

OBJECTIVES The present study constitutes the first randomized controlled trial to investigate the relation of lutein (L) and zeaxanthin (Z) to brain function using functional magnetic resonance imaging (fMRI). It was hypothesized that L and Z supplementation in older adults would enhance neural efficiency (i.e., reduce activation) and cognitive performance on a verbal learning task relative to placebo. METHODS A total of 44 community-dwelling older adults (mean age=72 years) were randomly assigned to receive either placebo or L+Z supplementation (12 mg/daily) for 1 year. Neurocognitive performance was assessed at baseline and post-intervention on an fMRI-adapted task involving learning and recalling word pairs. Imaging contrasts of blood-oxygen-level-dependent (BOLD) signal were created by subtracting active control trials from learning and recall trials. A flexible factorial model was employed to investigate the expected group (placebo vs. supplement) by time (baseline vs. post-intervention) interaction in pre-specified regions-of-interest. RESULTS L and Z appeared to buffer cognitive decline on the verbal learning task (Cohens d=.84). Significant interactions during learning were observed in left dorsolateral prefrontal cortex and anterior cingulate cortex (p < .05, family-wise-error corrected). However, these effects were in the direction of increased rather than decreased BOLD signal. Although the omnibus interaction was not significant during recall, within-group contrasts revealed significant increases in left prefrontal activation in the supplement group only. CONCLUSIONS L and Z supplementation appears to benefit neurocognitive function by enhancing cerebral perfusion, even if consumed for a discrete period of time in late life. (JINS, 2018, 24, 77-90).

Effects of Lutein/Zeaxanthin Supplementation on the Cognitive Function of Community Dwelling Older Adults: A Randomized, Double-Masked, Placebo-Controlled Trial

Background: High levels of xanthophyll carotenoids lutein (L) and zeaxanthin (Z) in the central nervous system have been previously correlated with improved cognitive function in community-dwelling older adults. In this study, we tested the effects of supplementing L and Z on older men and women with a range of baseline cognitive abilities. Objective: The purpose of this study was to determine whether or not supplementation with L+Z could improve cognitive function in community-dwelling, older adults. Design: Double-masked, randomized, placebo-controlled trial. A total of 62 older adults were randomized into groups receiving either 12 mg L+Z or a visually identical placebo. Data from 51 participants (M = 73.7 years) were available for analysis. Retinal L+Z levels (macular pigment optical density, MPOD) were measured psychophysically using heterochromatic flicker photometry as a biomarker of cortical L+Z levels. Cognitive function was measured using the CNS Vital Signs computerized test platform. Results: Participants receiving the active L+Z supplement had statistically significant increases in MPOD (p < 0.03) and improvements in complex attention (p < 0.02) and cognitive flexibility domains (p < 0.04), relative to participants taking the placebo. A trend was also seen for the executive function domain (p = 0.073). In male participants only, supplementation yielded improved composite memory (p = 0.04). Conclusions: Supplementation with L+Z improved cognitive function in community-dwelling, older men and women.

Delay and Probability Discounting as Candidate Markers for Dementia: An Initial Investigation

The present study investigated delay discounting and probability discounting-behavioral economic indices of impulsivity and risk proneness, respectively-in 39 healthy older adults and 25 older adults with mild cognitive impairment (MCI). Relative to the healthy group, it was hypothesized that older adults with MCI would display greater levels of impulsivity, risk proneness, and response inconsistency. The MCI group was found to display a unique delay discounting profile characterized by increasing impulsivity with decreasing reward magnitude, such that cognitively impaired older adults were significantly more impulsive than healthy controls at the small reward magnitude. The two groups exhibited similar levels of probability discounting, though older adults with MCI were significantly less consistent in their risk preferences. The present findings shed light onto decision-making in pre-dementia disease stages and suggest that discounting performance holds potential to complement early diagnostic instruments, likely due to pathophysiological processes in relevant brain regions.

Effects of a Lutein and Zeaxanthin Intervention on Cognitive Function: A Randomized, Double-Masked, Placebo-Controlled Trial of Younger Healthy Adults

Background: Past studies have suggested that higher lutein (L) and zeaxanthin (Z) levels in serum and in the central nervous system (as quantified by measuring macular pigment optical density, MPOD) are related to improved cognitive function in older adults. Very few studies have addressed the issue of xanthophylls and cognitive function in younger adults, and no controlled trials have been conducted to date to determine whether or not supplementation with L + Z can change cognitive function in this population. Objective: The purpose of this study was to determine whether or not supplementation with L + Z could improve cognitive function in young (age 18–30), healthy adults. Design: A randomized, double-masked, placebo-controlled trial design was used. Fifty-one young, healthy subjects were recruited as part of a larger study on xanthophylls and cognitive function. Subjects were randomized into active supplement (n = 37) and placebo groups (n = 14). MPOD was measured psychophysically using customized heterochromatic flicker photometry. Cognitive function was measured using the CNS Vital Signs testing platform. MPOD and cognitive function were measured every four months for a full year of supplementation. Results: Supplementation increased MPOD significantly over the course of the year, vs. placebo (p < 0.001). Daily supplementation with L + Z and increases in MPOD resulted in significant improvements in spatial memory (p < 0.04), reasoning ability (p < 0.05) and complex attention (p < 0.04), above and beyond improvements due to practice effects. Conclusions: Supplementation with L + Z improves CNS xanthophyll levels and cognitive function in young, healthy adults. Magnitudes of effects are similar to previous work reporting correlations between MPOD and cognition in other populations.

Discounting preferences and response consistency as markers of functional ability in community-dwelling older adults

Introduction: Predictors of functional independence in older adults are in need. Based on findings that delay discounting, probability discounting, and the ability to respond consistently use cognitive abilities and neural systems with central relevance to functional ability, the present study evaluated whether these behavioral economic variables account for variance in everyday functioning in older adults. It was hypothesized that greater preference for immediate/probabilistic rewards and response inconsistency would independently predict decrements in instrumental activities of daily living (IADLs). Method: Participants included 64 community-dwelling older adults (65–85 years; mean age = 76.25 years; 76.60% female). Exclusionary criteria were neurological illness, illiteracy, substance dependence within the past 5 years, score of ≤20 on the Mini-Mental State Examination, and/or presence of dementia. Delay/probability discounting tasks consisted of a series of dichotomous selections between smaller, immediate/guaranteed and larger, delayed/probabilistic monetary values. Area under the curve (AUC) was used to index levels of discounting, while response (in)consistency was based on the percentage of contradictory responses. The Direct Assessment of Functional Status–Revised (DAFS–R) provided a performance-based assessment of IADLs. Hierarchical regression analyses were conducted to determine whether discounting preferences and response consistency accounted for variance in functional ability over and above relevant demographic characteristics. Results: Demographic characteristics accounted for significance variance in IADLs (p = .001, R2 = .237). Probability discounting AUC (p = .014, ΔR2 = .075) and response (in)consistency (p = .046, ΔR2 = .050) each accounted for significant additional variance in functional ability, as did delay discounting response (in)consistency (p = .010, ΔR2 = .081). Delay discounting AUC did not add significantly to the model (p = .861). Conclusions: Discounting preferences and choice consistency hold potential to serve as relatively fast and inexpensive markers of functional decline, likely due to neurocognitive deterioration relevant to both behavioral economic decision making and functional independence.

Lutein and Zeaxanthin Are Positively Associated with Visual–Spatial Functioning in Older Adults: An fMRI Study

Lutein (L) and zeaxanthin (Z) are two xanthophyll carotenoids that have antioxidant and anti-inflammatory properties. Previous work has demonstrated their importance for eye health and preventing diseases such as age-related macular degeneration. An emerging literature base has also demonstrated the importance of L and Z in cognition, neural structure, and neural efficiency. The present study aimed to better understand the mechanisms by which L and Z relate to cognition, in particular, visual–spatial processing and decision-making in older adults. We hypothesized that markers of higher levels of L and Z would be associated with better neural efficiency during a visual–spatial processing task. L and Z were assessed via standard measurement of blood serum and retinal concentrations. Visual–spatial processing and decision-making were assessed via a judgment of line orientation task (JLO) completed during a functional magnetic resonance imaging (fMRI) scan. The results demonstrated that individuals with higher concentrations of L and Z showed a decreased blood-oxygen-level dependent (BOLD) signal during task performance (i.e., “neural efficiency”) in key areas associated with visual–spatial perception, processing, decision-making, and motor coordination, including the lateral occipital cortex, occipital pole, superior and middle temporal gyri, superior parietal lobule, superior and middle frontal gyri, and pre- and post-central gyri. To our knowledge, this is the first investigation of the relationship of L and Z to visual–spatial processing at a neural level using in vivo methodology. Our findings suggest that L and Z may impact brain health and cognition in older adults by enhancing neurobiological efficiency in a variety of regions that support visual perception and decision-making.

Education Differentially Buffers Cognitive Performance in Black and White Older Adults

Objectives Given that black American older adults are more likely to have lower educational attainment and perform worse on cognitive tests than white Americans, we examined whether increased education would confer greater cognitive advantage to black Americans on measures of global and specific domains of cognitive function. Methods The sample included 522 community-dwelling older adults from a larger study. An analysis of covariance was conducted with race and education as between-participant factors and global cognition as the dependent variable. A multivariate analysis of covariance was conducted with five cognitive domains (immediate memory, visuospatial/constructional ability, language, attention, and delayed memory) as the dependent variables. Results Significant main effects indicated that black Americans, F(1,516) = 29.18, p < .001, and individuals with less education, F(1,516) = 44.93, p < .001, evidenced lower cognitive functioning, controlling for age and overall health status, and the interaction term reached statistical significance, F(1,516) = 7.95, p = .005. The impact of education on global cognitive function for black participants was more than twice as large (Cohens d = 1.30) than for white participants (Cohens d = .52). There was a significant race × education interaction for the cognitive domain of attention (p < .001) and a composite measure of non-memory domains (i.e., language, visuospatial/constructional, and attention; p < .001). Discussion Our findings suggest that educational attainment is particularly important for black Americans with respect to global cognitive function, attention, and non-memory domains.

Personality's association with IADLs in community dwelling older adults

Extant research has established several predictors of functional ability (FA) in older adults (OAs); however, one factor that has been relatively ignored is personality. Preliminary evidence suggests that openness and agreeableness are associated with instrumental activities of daily living (IADLs). However, how personality is related to IADLs remains unclear. We aimed to determine how personality factors predict performance of IADLs, which we hypothesized, was because of executive functioning (EF).

Executive function moderates the relationship between physical performance and functional independence in older adults

We translated the test “partial knowledge of abstract words” into Thai and investigated the occurrence of partial knowledge effects in the conceptual domain of abstract words in individuals with frontotemporal dementia-semantic dementia (FTD-SD), Alzheimer disease (AD), and other dementia. Twelve FTD-SD, 14 AD, 7 non-amnestic mild cognitive impairment (non-am MCI), 3 other dementia, and 10 healthy controls were examined with 3 level synonym comprehension abstract word test. They include antonym distractors, distant distractors, and close distractors. Results: Mean scores of the antonym distractors, distant distractors, and close distractors of dementia groups and controls were displayed in figure 1. All dementia groups showed weaker performance on choosing distant distractors and close distractors, which requires a fine specification of word meaning, than controls. The impairment of partial knowledge of abstract words was greater in those with SD than AD compared to controls (SD: antonym distractor SE1⁄43.43 p1⁄40.034, distant distractors SE1⁄43.36, p1⁄40.001, close distractor SE 1⁄42.69, p1⁄40.002; AD: antonym distractor SE1⁄43.31, p1⁄40.03, distant distractors SE1⁄43.25, p1⁄40.005, close distractor SE1⁄42.6, p1⁄40.016). We found that 3 subjects with Parkinson dementia and vascular dementia performed worst. However, the number of subjects in this group was small. Conclusions: These findings demonstrate that a degraded conceptual knowledge of abstract words is a phenomenon in neurodegenerative diseases and vascular dementia. Detailed information of abstract words is more affected than broad-sense information.