Proxy Measures Of Cognitive Reserve Research Articles

Cognitive reserve and dementia risk management in people with an intellectual disability.

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Proxy measures of cognitive reserve and trajectories of gait and cognitive decline in older adults

AbstractBackgroundLifestyle interventions are an emerging area of interest in dementia prevention. Education, physical activity, and social interactions are potentially modifiable lifestyle factors that are considered proxies of cognitive reserve. People with greater cognitive reserve could be protected against decline in gait and cognition, two interrelated problems associated with dementia, by coping better with age‐ or pathology‐related brain changes. We examined whether decline in gait and cognitive functions are different in those with higher versus lower levels of education, physical activity, and social interactions.MethodGait and cognitive performance in 1,095 LonGenity study participants (mean age = 75.4±6.7 years) that were free of dementia at baseline were examined up to 12 years. Gait speed was measured during usual pace (single‐task walking, STW‐speed) and walking‐while‐talking (WWT‐speed). Cognitive performance was measured with standard neuropsychological tests and a standardized composite global cognitive measure was derived. Years of education, number of blocks walked per day, living with someone and engaging in paid or volunteer work (markers of social interactions) were obtained from self‐report. Linear mixed‐effects models adjusted for sex, parental longevity, cognitive impairment, and global health were used to examine age‐associated changes in gait and cognition in those with and without greater cognitive reserve.ResultSTW‐speed and WWT‐speed did not vary as a function of education, physical activity, or social interactions. Greater number of blocks walked per day was associated with slower decline in global cognition, Trail Making Test (TMT)‐A, TMT‐interference, digit symbol substitution, logical memory, figure recall, free recall, category and phonemic fluency tests. Higher education was associated with slower decline in global cognition, TMT‐interference, TMT‐A and figure copy task. Living with someone was associated with slower decline in global cognition, digit symbol substitution and logical memory. Paid or volunteer work was associated slower decline in global cognition.ConclusionHaving higher education, more physical activity and social interactions appear to protect against cognitive, but not gait decline, potentially by building up cognitive reserve. The multifaceted etiology and relatively earlier decline of gait may render it less influenced by potentially modifiable risk factors in late life than cognition.

Verbal intelligence is a more robust cross-sectional measure of cognitive reserve than level of education in healthy older adults

BackgroundCognitive reserve is most commonly measured using socio-behavioural proxy variables. These variables are easy to collect, have a straightforward interpretation, and are widely associated with reduced risk of dementia and cognitive decline in epidemiological studies. However, the specific proxies vary across studies and have rarely been assessed in complete models of cognitive reserve (i.e. alongside both a measure of cognitive outcome and a measure of brain structure). Complete models can test independent associations between proxies and cognitive function in addition to the moderation effect of proxies on the brain-cognition relationship. Consequently, there is insufficient empirical evidence guiding the choice of proxy measures of cognitive reserve and poor comparability across studies.MethodIn a cross-sectional study, we assessed the validity of 5 common proxies (education, occupational complexity, verbal intelligence, leisure activities, and exercise) and all possible combinations of these proxies in 2 separate community-dwelling older adult cohorts: The Irish Longitudinal Study on Ageing (TILDA; N = 313, mean age = 68.9 years, range = 54–88) and the Cognitive Reserve/Reference Ability Neural Network Study (CR/RANN; N = 234, mean age = 64.49 years, range = 50–80). Fifteen models were created with 3 brain structure variables (grey matter volume, hippocampal volume, and mean cortical thickness) and 5 cognitive variables (verbal fluency, processing speed, executive function, episodic memory, and global cognition).ResultsNo moderation effects were observed. There were robust positive associations with cognitive function, independent of brain structure, for 2 individual proxies (verbal intelligence and education) and 16 composites (i.e. combinations of proxies). Verbal intelligence was statistically significant in all models. Education was significant only in models with executive function as the cognitive outcome variable. Three robust composites were observed in more than two-thirds of brain-cognition models: the composites of (1) occupational complexity and verbal intelligence, (2) education and verbal intelligence, and (3) education, occupational complexity, and verbal intelligence. However, no composite had larger average effects nor was more robust than verbal intelligence alone.ConclusionThese results support the use of verbal intelligence as a proxy measure of CR in cross-sectional studies of cognitively healthy older adults.

Cognitive Reserve and Driving-Related Cognitive Abilities in a Sample of Oldest Old Drivers Undergoing Assessment of Fitness to Drive.

This study examines the relationship between age, cognitive reserve (CR), and driving-related cognitive abilities in a sample of oldest old drivers undergoing evaluation of fitness to drive. Structural equation modeling was used to investigate the associations between age, CR, and performances to a standardized set of cognitive tests assessing fitness to drive. Education and work complexity were used as proxy measures of CR. The results showed both measures of CR, but not age, were significantly associated with higher general intelligence. Education also predicted higher decision speed, and decision speed partly mediated the effect of education on general intelligence. These findings suggest that over age of 80 years old, CR was a better predictor of driving-related cognitive abilities than age. Education was associated with better performance across different cognitive domains including processing speed.

Validation of composite proxy measures of cognitive reserve: What can longitudinal cohorts tell us about the association between modifiable dementia risk factors and the ageing

Validation of composite proxy measures of cognitive reserve: What can longitudinal cohorts tell us about the association between modifiable dementia risk factors and the ageing

Validation of composite proxy measures of cognitive reserve

AbstractBackgroundCognitive reserve (CR) enables individuals to maintain cognitive function despite the presence of brain pathology or atrophy [1]. CR is typically measured via proxy variables that reflect exposure to lifetime experiences, such as education [2]. Composite measures of multiple proxies combine contributions from several experiences and display consistent positive relationships with cognitive function [3]. However, the optimal set of proxies for inclusion in composite measures remains to be determined [2]. Here, we aimed to identify a combination of proxies that best reflects the ability to maintain cognitive function despite cortical thinning.MethodAs part of a larger analysis, 277 healthy adult participants provided data for this study (mean age = 69.18, SD age = 6.66, 141 females). Global cognition was defined as average of z‐scores from the Animal Naming task, Colour Trails Test 1 and 2, Immediate and Delayed Recall. Mean cortical thickness was calculated using FreeSurfer using a previously reported method [4]. CR proxies were: educational attainment, occupational complexity, premorbid intelligence, social engagement, cognitively stimulating activity, leisure activity, and physical activity. For each composite, a three‐step hierarchical‐multiple regression was performed to predict global cognition. Independent variables in Step 1 were age, gender, cortical thickness, CR composite was added in Step 2, and an interaction term (cortical thickness*composite) was further added in Step 3. Positive associations between CR composites and global cognition – independent of age, gender and cortical thickness – were ranked on significant R‐squared change values from Step 1 to Step 2. Moderation effects were identified by significant R‐squared change values from Step 2 to Step 3.ResultMost CR composites had positive associations with global cognition, independent of age, gender, and cortical thickness (see Figure 1). A CR composite measuring cognitively stimulating activity, leisure activity, and physical activity had the biggest negative moderation effect (R2 change = 0.013, p = 0.0276) on the cortical thickness‐global cognition relationship.ConclusionA composite measure of cognitively stimulating‐, leisure‐, and physical‐activity, displays construct validity as a measure of CR in addition to a wide range of composites which display positive, independent, associations with cognitive function.

The association between cognitive reserve and performance-related brain activity during episodic encoding and retrieval across the adult lifespan

Remembering associations between encoded items and their contextual setting is a feature of episodic memory. Although this ability generally deteriorates with age, there is substantial variability in how older individuals perform on episodic memory tasks. A current topic of debate in the cognitive neuroscience of aging literature revolves around whether this variability may stem from genetic and/or environmental factors related to reserve, allowing some individuals to compensate for age-related decline through differential recruitment of brain regions. In this fMRI study spanning a large adult lifespan sample (N = 154), we tested whether higher cognitive reserve was associated with better task-fMRI context memory performance, and functional compensatory activity patterns in the aging brain. We used multivariate Behaviour Partial Least Squares (B-PLS) analysis to examine how age, retrieval accuracy, and a proxy measure of cognitive reserve [i.e., a composite score consisting of years of education (EDU) and crystallized IQ], impacted brain activity during the encoding and retrieval of spatial and temporal contextual details. The results indicated that age-related increases in encoding activity within anterior and lateral frontal, inferior parietal, occipito-temporal and medial temporal cortices, was correlated with better subsequent memory performance; and may be indicative of age-related functional compensation at encoding. Interestingly this compensatory pattern was not correlated with our proxy measure of cognitive reserve but was associated with total brain volume (a measure of brain reserve). However, cognitive reserve was associated with age-invariant and task-general activity in superior temporal, occipital, and left inferior frontal regions. We conclude that the relationship between cognitive reserve, brain reserve and age-related functional compensation is complex, and that EDU and IQ may not fully account for individual differences in cognitive reserve when studying well educated, healthy aging cohorts.

Expanding the role of education in frontotemporal dementia: a functional dynamic connectivity (the chronnectome) study

In the present study, we aim at investigating whether education modulates dynamical properties of time-varying whole-brain network connectivity (the chronnectome) in frontotemporal dementia (FTD) at a given level of symptom severity. Dynamic connectivity parameters were evaluated in 128 patients with FTD using independent component analysis, sliding-time window correlation, and k-means approach to resting state–magnetic resonance imaging data. We evaluated the relationship between education, a proxy measure of cognitive reserve, and 4 indexes of metastate dynamic connectivity: (1) the number of distinct metastates a patient passes through, (2) the number of switches from one metastate to another, (3) the span of the realized metastates, and (4) the total distance traveled in the state space. We found a significant inverse correlation between years of education and the 4 indexes of metastate dynamic fluidity (all p-values ≤ 0.03, false discovery rate–corrected). This study suggests that patients with FTD with higher education but comparable clinical severity show more global functional brain impairment, suggesting that patients with higher cognitive reserve can cope with more global brain fluidity reduction.

Defining Cognitive Reserve and Implications for Cognitive Aging.

The aim of this review is to summarize current conceptual models of cognitive reserve (CR) and related concepts and to discuss evidence for these concepts within the context of aging and Alzheimer's disease. Evidence to date supports the notion that higher levels of CR, as measured by proxy variables reflective of lifetime experiences, are associated with better cognitive performance, and with a reduced risk of incident mild cognitive impairment/dementia. However, the impact of CR on longitudinal cognitive trajectories is unclear and may be influenced by a number of factors. Although there is promising evidence that some proxy measures of CR may influence structural brain measures, more research is needed. The protective effects of CR may provide an important mechanism for preserving cognitive function and cognitive well-being with age, in part because it can be enhanced throughout the lifespan. However, more research on the mechanisms by which CR is protective is needed.

Development and initial validation of the Retrospective Indigenous Childhood Enrichment scale (RICE).

294 Aboriginal Australian people (60-92 years), living in urban or regional areas of NSW, completed the RICE scale as part of a longer face-to-face interview. Additional data was collected on their formal education, childhood environment, and childhood trauma (Study 1). Test-retest, inter-method and inter-rater reliability were assessed in a convenience sample of a further 38 participants by re-administration of the RICE scale at two time points, approximately 14 days apart (M = 14.11, SD = 6.78) (Study 2). Factor analyses reduced the scale from 21 items to 18 and identified three factors: (1) Traditional, (2) Intellectual, and (3) Community. Higher scores on the RICE scale were related to higher years of formal education and lower scores on a childhood trauma questionnaire. The RICE scale had good internal consistency (Cronbach's α 0.79), and excellent test-retest reliability (ICC = 0.95, 95% CI 0.90-0.97) and inter-rater reliability (0.99, CI 95% 0.997-0.999). The RICE is, to our knowledge, the first standardized measure that assesses the level of childhood environmental stimulation in older Aboriginal Australians. This could provide an important supplementary measure, in addition to formal education, to investigate cognitive reserve and dementia risk in this population and enhance understanding of the links between childhood experiences and late-life cognitive decline.

Urban residence and higher education do not protect against cognitive decline in aging and dementia: 10-year follow-up of the Canadian Study of Health and Aging

ABSTRACTThe construct of cognitive reserve has primarily been defined in terms of a single proxy measure, education. There may, however, be alternative, potentially additive, proxy measures of cognitive reserve, such as rural or urban residence. Using a large sample of 10,263 older Canadians, ranging in age between 64 and 99 years (mean age = 75.7 years, SD = 7.1), residents of rural and urban areas were compared using the Modified Mini-Mental State (3MS) examination as a dependent variable. Within this sample, subsamples of demented and non-demented individuals were investigated. The 3MS data were analyzed using a linear mixed model with years of education and residence as proxies of cognitive reserve and time of testing (linear and quadratic) as a within-groups variable. All predictor variables in the model (i.e., gender, age, education, residence, and time of testing) had a significant impact on cognitive functioning. The results showed that, although urban residents and higher educated individuals performed better than rural residents and lower educated individuals at baseline, these performance benefits were nullified at 10-year follow-up. The disappearance of these initial performance benefits suggests that urban dwellers and higher educated individuals are not protected against age-related cognitive decline. Thus, no support was found for the cognitive reserve hypothesis.

The effects of lifelong cognitive lifestyle on executive function in older people with Parkinson's disease.

Active lifelong cognitive lifestyles increase cognitive reserve and have beneficial effects on global cognition, cognitive decline and dementia risk in Parkinson's disease (PD). Executive function is particularly impaired even in early PD, and this impacts on quality of life. The effects of lifelong cognitive lifestyle on executive function in PD have not been studied previously. This study examined the association between lifelong cognitive lifestyle, as a proxy measure of cognitive reserve, and executive function in people with PD. Sixty-nine people diagnosed with early PD without dementia were recruited as part of the Bilingualism as a protective factor in Age-related Neurodegenerative Conditions study. Participants completed a battery of tests of executive function. The Lifetime of Experiences Questionnaire was completed as a comprehensive assessment of lifelong cognitive lifestyle. Non-parametric correlations compared clinical measures with executive function scores. Cross-sectional analyses of covariance were performed comparing the performance of low and high cognitive reserve groups on executive function tests. Correlational analyses showed that better executive function scores were associated with younger age, higher levodopa dose and higher Lifetime of Experiences Questionnaire scores. Higher cognitive reserve was associated with better motor function, but high and low cognitive reserve groups did not differ in executive function. Cognitive reserve, although associated with global cognition, does not appear to be associated with executive function. This differential effect may reflect the specific cognitive profile of PD. The long-term effects of cognitive reserve on executive function in PD require further exploration. Copyright © 2017 John Wiley & Sons, Ltd.

Cognitive reserve moderates long-term cognitive and functional outcome in cerebral small vessel disease

BackgroundCerebral small vessel disease (SVD) is characterised by progressive white matter hyperintensities (WMH), cognitive decline and loss of functional independence. The correspondence between neuroimaging findings and the severity of clinical...

Middle age self-report risk score predicts cognitive functioning and dementia in 20–40 years

IntroductionOn the basis of the proxy measures of cognitive reserve, we created a middle age self-report risk score for early prediction of dementia. MethodsWe used a longitudinal population-based study of 2602 individuals with a replication sample (N = 1011). Risk score at a mean age of 47 years was based on questions on educational and occupational attainments. Cognitive status at a mean age of 74 was determined via two validated telephone instruments. ResultsThe prevalence of dementia was 10% after a mean follow-up of 28 years. Risk score was a good predictor of dementia: area under the curve = 0.77 (95% confidence interval, 0.74–0.80). The risk of dementia decreased as a function of risk score from 36% to 0%. The risk score was significantly associated with cognition after a mean follow-up of 39 years in the replication sample. DiscussionSelf-report risk score predicted cognitive functioning and dementia risk 20–40 years later.

Does cognitive reserve moderate the association between mood and cognition? A systematic review

SummaryThe evidence regarding the association between mood and cognitive function is conflicting, suggesting the involvement of moderating factors. This systematic review aimed to assess whether cognitive reserve moderates the association between mood and cognition in older people. Cognitive reserve was considered in terms of the three key proxy measures – educational level, occupation, and engagement in cognitively stimulating leisure activities – individually and in combination. Sixteen studies representing 37,101 participants were included in the review. Of these, 13 used a measure of education, one used a measure of occupation, two used a measure of participation in cognitively stimulating activities, and one used a combination of these. In general, cognitive reserve moderated the association between mood and cognition, with a larger negative association between mood and cognition in those with low cognitive reserve than in those with high cognitive reserve. Further research utilizing multiple proxy measures of cognitive reserve is required to elucidate the associations.

A Life Course Model of Cognitive Activities, Socioeconomic Status, Education, Reading Ability, and Cognition

To cross-sectionally quantify the contribution of proxy measures of cognitive reserve reflective of the lifespan, such as education, socioeconomic status (SES), reading ability, and cognitive activities, in explaining late-life cognition. Prospective observational cohort study of aging. Retirement communities across the Chicago metropolitan area. Nine hundred fifty-one older adults free of clinical dementia in the Rush Memory and Aging Project (aged 79 ± 8, 74% female). Baseline data on multiple life course factors included early-, mid-, and late-life participation in cognitive activities; early-life and adult SES; education; and reading ability (National Adult Reading Test; NART). Path analysis quantified direct and indirect standardized effects of life course factors on global cognition and five cognitive domains (episodic memory, semantic memory, working memory, visuospatial ability, perceptual speed). Adjusting for age, sex, and race, education had the strongest association with global cognition, episodic memory, semantic memory, and visuospatial ability, whereas NART (followed by education) had the strongest association with working memory. Late-life cognitive activities had the strongest association with perceptual speed, followed by education. These cross-sectional findings suggest that education and reading ability are the most-robust proxy measures of cognitive reserve in relation to late-life cognition. Additional research leveraging path analysis is warranted to better understand how these life course factors, reflecting the latent construct of cognitive reserve, affect abnormal cognitive aging.

The response-signal method reveals age-related changes in object working memory.

Sixteen healthy young adults (ages 18-32) and 16 healthy older adults (ages 67-81) completed a delayed response task in which they saw the following visual sequence: memory stimuli (2 abstract shapes; 3,000 ms), a blank delay (5,000 ms), a probe stimulus of variable duration (one abstract shape; 125, 250, 500, 1,000, or 2,000 ms), and a mask (500 ms). Subjects decided whether the probe stimulus matched either of the memory stimuli; they were instructed to respond during the mask, placing greater emphasis on speed than accuracy. The authors used D. L. Hintzman & T. Curran's (1994) 3-parameter compound bounded exponential model of speed-accuracy tradeoff to describe changes in discriminability associated with total processing time. Group-level analysis revealed a higher rate parameter and a higher asymptote parameter for the young adult group, but no difference across groups in x-intercept. Proxy measures of cognitive reserve (Y. Stern et al., 2005) predicted the rate parameter value, particularly in older adults. Results suggest that in working memory, aging impairs both the maximum capacity for discriminability and the rate of information accumulation, but not the temporal threshold for discriminability.