Meghan B. Mitchell

Prediction of functional status in older adults: the ecological validity of four Delis-Kaplan Executive Function System tests.

This study tested the ecological validity of four Delis-Kaplan Executive Function System (D-KEFS) tests by examining how well performance on D-KEFS measures predicted observed daily functioning in community-dwelling older adults. Older adults ages 65 to 92 years completed four D-KEFS tests requiring planning and cognitive fluency. The four combined D-KEFS measures accounted for approximately 26% of the variance in observed functional ability, when controlling for education and depression, thus supporting the ecological validity of the D-KEFS (Pearson r = .66). However, in a multiple regression analysis, the D-KEFS Trail Making Test-4 was the only measure of executive functioning that accounted for unique, independent variance in observed functional ability.

A web-based normative calculator for the uniform data set (UDS) neuropsychological test battery

IntroductionWith the recent publication of new criteria for the diagnosis of preclinical Alzheimers disease (AD), there is a need for neuropsychological tools that take premorbid functioning into account in order to detect subtle cognitive decline. Using demographic adjustments is one method for increasing the sensitivity of commonly used measures. We sought to provide a useful online z-score calculator that yields estimates of percentile ranges and adjusts individual performance based on sex, age and/or education for each of the neuropsychological tests of the National Alzheimers Coordinating Center Uniform Data Set (NACC, UDS). In addition, we aimed to provide an easily accessible method of creating norms for other clinical researchers for their own, unique data sets.MethodsData from 3,268 clinically cognitively-normal older UDS subjects from a cohort reported by Weintraub and colleagues (2009) were included. For all neuropsychological tests, z-scores were estimated by subtracting the raw score from the predicted mean and then dividing this difference score by the root mean squared error term (RMSE) for a given linear regression model.ResultsFor each neuropsychological test, an estimated z-score was calculated for any raw score based on five different models that adjust for the demographic predictors of SEX, AGE and EDUCATION, either concurrently, individually or without covariates. The interactive online calculator allows the entry of a raw score and provides five corresponding estimated z-scores based on predictions from each corresponding linear regression model. The calculator produces percentile ranks and graphical output.ConclusionsAn interactive, regression-based, normative score online calculator was created to serve as an additional resource for UDS clinical researchers, especially in guiding interpretation of individual performances that appear to fall in borderline realms and may be of particular utility for operationalizing subtle cognitive impairment present according to the newly proposed criteria for Stage 3 preclinical Alzheimers disease.

Cognitively Stimulating Activities: Effects on Cognition across Four Studies with up to 21 Years of Longitudinal Data

Engagement in cognitively stimulating activities has been considered to maintain or strengthen cognitive skills, thereby minimizing age-related cognitive decline. While the idea that there may be a modifiable behavior that could lower risk for cognitive decline is appealing and potentially empowering for older adults, research findings have not consistently supported the beneficial effects of engaging in cognitively stimulating tasks. Using observational studies of naturalistic cognitive activities, we report a series of mixed effects models that include baseline and change in cognitive activity predicting cognitive outcomes over up to 21 years in four longitudinal studies of aging. Consistent evidence was found for cross-sectional relationships between level of cognitive activity and cognitive test performance. Baseline activity at an earlier age did not, however, predict rate of decline later in life, thus not supporting the concept that engaging in cognitive activity at an earlier point in time increases ones ability to mitigate future age-related cognitive decline. In contrast, change in activity was associated with relative change in cognitive performance. Results therefore suggest that change in cognitive activity from ones previous level has at least a transitory association with cognitive performance measured at the same point in time.

Cognitive performance in centenarians and the oldest old: norms from the Georgia Centenarian Study.

ABSTRACT We present normative data from a large population-based sample of centenarians for several brief, global neurocognitive tasks amenable for frail elders. Comparative data from octogenarians are included. A total of 244 centenarians and 80 octogenarians from Phase III of the Georgia Centenarian Study were administered the Mini-Mental Status Examination, Severe Impairment Battery, and Behavioral Dyscontrol Scale. Centenarians (age 98–107) were stratified into three age cohorts (98–99, 100–101, 102–107), octogenarians into two 5- year cohorts (80–84, 85–89). Highly significant differences were observed between groups on all measures, with greater variation and dispersion in performance among centenarians, as well as stronger associations between age and performance. Descriptive statistics and normative ranges (unweighted and population-weighted) are provided by age cohort. Additional statistics are provided by education level. While most previous centenarian studies have used convenience samples, ours is population-based and likely more valid for comparison in applied settings. Results suggest centenarians look different than do even the oldest age range of most normative aging datasets (e.g., 85–90). Results support using global measures of neurocognition to describe cognitive status in the oldest old, and we provide normative comparisons to do so.

Executive Functioning and Observed Versus Self-Reported Measures of Functional Ability

This study investigated the relationship between measures of executive functioning and both observed and self-reported functional ability. It was hypothesized that performance on a direct assessment of functional ability would have a stronger correlation with performance on measures of executive functioning than a self-report measure of functional ability. Results supported the hypothesis, indicating that self-report measures may not be sensitive to early decline in functional ability. Results also provide evidence to support the use of measures of executive functioning to detect early decline in functional ability that otherwise may not be detected by the typical self-report measures used in clinical settings. While lack of insight into functional deficits has been demonstrated in the literature in older adults with dementia, this study demonstrated lack of insight in a non-demented, community dwelling sample of older adults.

Dynamic Associations of Change in Physical Activity and Change in Cognitive Function: Coordinated Analyses of Four Longitudinal Studies

The present study used a coordinated analyses approach to examine the association of physical activity and cognitive change in four longitudinal studies. A series of multilevel growth models with physical activity included both as a fixed (between-person) and time-varying (within-person) predictor of four domains of cognitive function (reasoning, memory, fluency, and semantic knowledge) was used. Baseline physical activity predicted fluency, reasoning and memory in two studies. However, there was a consistent pattern of positive relationships between time-specific changes in physical activity and time-specific changes in cognition, controlling for expected linear trajectories over time, across all four studies. This pattern was most evident for the domains of reasoning and fluency.

Anti-RAGE and Aβ Immunoglobulin Levels Are Related to Dementia Level and Cognitive Performance

BACKGROUND Blood-based immunoglobulins (IgGs) may mark the presence of amyloid plaques characterizing the progression of Alzheimers disease (AD). Previous studies suggest that anti-RAGE and anti-Abeta IgGs increase proportionately with accumulation of amyloid-beta (Abeta) peptides at receptor sites for advanced glycation end products (RAGE), within cortical areas of brain tissue. We assessed the relationship between these potential markers and an AD-type cognitive profile. We hypothesized that these specific IgG levels would be positively correlated with Clinical Dementia Rating (CDR) scores as well as index scores on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) in domains associated with cortical function. METHODS Participants were 118 older adults (mean age = 74, standard deviation = 10.5) drawn from the community and local physician referrals. Participants were reassigned into five groups based on CDR. Blood IgG levels were determined through an affinity purification process. RESULTS Analysis of covariance analyses revealed that CDR scores were significantly related to anti-RAGE, F(4,106) = 12.93, p < .001, and anti-Abeta, F(4,106) = 17.08, p < .001, after controlling for age and total IgG levels. Regression analyses indicated significant variance accounted for by anti-RAGE and anti-Abeta above and beyond total IgG effects. Additional regression identified specific RBANS domains accounting for significant variance in anti-RAGE levels including language (t = -3.74, p < .001) and delayed memory (t = -2.31, p < .05), whereas language accounted for a significant amount of variance in anti-Abeta levels (t = -3.96, p < .001). CONCLUSIONS Anti-RAGE and anti-Abeta IgGs correlate strongly with global scores of dementia. Furthermore, they are associated with a profile of deficiency in domains associated with specific cortical function. Results suggest potential for anti-Abeta and anti-RAGE IgGs as blood biomarkers for AD.

Social Activity and Cognitive Functioning Over Time: A Coordinated Analysis of Four Longitudinal Studies

Social activity is typically viewed as part of an engaged lifestyle that may help mitigate the deleterious effects of advanced age on cognitive function. As such, social activity has been examined in relation to cognitive abilities later in life. However, longitudinal evidence for this hypothesis thus far remains inconclusive. The current study sought to clarify the relationship between social activity and cognitive function over time using a coordinated data analysis approach across four longitudinal studies. A series of multilevel growth models with social activity included as a covariate is presented. Four domains of cognitive function were assessed: reasoning, memory, fluency, and semantic knowledge. Results suggest that baseline social activity is related to some, but not all, cognitive functions. Baseline social activity levels failed to predict rate of decline in most cognitive abilities. Changes in social activity were not consistently associated with cognitive functioning. Our findings do not provide consistent evidence that changes in social activity correspond to immediate benefits in cognitive functioning, except perhaps for verbal fluency.

Activities of Daily Living Are Associated With Older Adult Cognitive Status: Caregiver Versus Self-Reports

We compared the extent to which subjective report of activities of daily living (ADLs) by caregivers and older adults were associated with objective measures of older adults’ cognition. In independent studies (Study 1 N = 238; Study 2 N = 295), bivariate correlations and multiple regression analyses examined the association of caregiver and self-rated reports of older adult basic, instrumental, and total ADLs and older adult cognition. We examined the magnitude of the caregiver/self-report discrepancy and older adult cognition. In both studies, caregiver reports more accurately accounted for older adult cognitive differences. Older adult visuospatial/constructional deficits were uniquely related to caregiver basic ADL reports. Results indicate that caregiver reports of older adult ADLs are more reliable indicators of older adult cognition than self-reports, and this difference grows as older adult cognition decreases. Thus, older adult ADL assessment may be useful in providing information on potential cognitive decline.

Neuropsychological Test Performance and Cognitive Reserve in Healthy Aging and the Alzheimer's Disease Spectrum: A Theoretically Driven Factor Analysis

Accurate measurement of cognitive function is critical for understanding the disease course of Alzheimers disease (AD). Detecting cognitive change over time can be confounded by level of premorbid intellectual function or cognitive reserve and lead to under- or over-diagnosis of cognitive impairment and AD. Statistical models of cognitive performance that include cognitive reserve can improve sensitivity to change and clinical efficacy. We used confirmatory factor analysis to test a four-factor model composed of memory/language, processing speed/executive function, attention, and cognitive reserve factors in a group of cognitively healthy older adults and a group of participants along the spectrum of amnestic mild cognitive impairment to AD (aMCI-AD). The model showed excellent fit for the control group (χ(2) = 100; df = 78; CFI = .962; RMSEA = .049) and adequate fit for the aMCI-AD group (χ(2) = 1750; df = 78; CFI = .932; RMSEA = .085). Although strict invariance criteria were not met, invariance testing to determine if factor structures are similar across groups yielded acceptable absolute model fits and provide evidence in support of configural, metric, and scalar invariance. These results provide further support for the construct validity of cognitive reserve in healthy and memory impaired older adults.