Exploring strategies to operationalize cognitive reserve: A systematic review of reviews

Cardiometabolic Risk and Cognitive Decline: The Role of Socioeconomic Status in Childhood and Adulthood

Socioeconomic conditions in childhood predict cognitive functioning in later life. It is unclear whether poor childhood socioeconomic status (SES) also predicts the acceleration of cognitive decline. One proposed pathway is via cardiometabolic risk, which has been linked to both childhood SES and earlier onset of cognitive impairment. Using data from the Health and Retirement Study, we examine the impact of childhood SES on cognitive trajectories over six years and test whether it operates through increased cardiometabolic risk and adult SES. We find that higher childhood SES leads to slower cognitive decline, partially due to lower levels of cardiometabolic risk. However, these pathways operate entirely through adult socioeconomic attainment. The results have important implications for future trends in cognitive population health within the context of growing social inequality and reduced social mobility.

Cohort Effects in Progression Rate on Cognitive and Functional Measures in an Alzheimer's Disease Clinical Cohort

BACKGROUND

Accurate prediction of Alzheimer's disease (AD) cognitive and functional outcomes in clinical research requires consistent underlying rates of change over time.

OBJECTIVE

To examine cohort effects in AD progression rate over five years of follow-up using a clinical database of probable AD patients.

METHODS

Baseline characteristics of three cohorts enrolled from 1995-1999, 2000-2004, and 2005-2009 were compared using ANOVA and chi-square tests. Differences in 5-year decline on the Mini-Mental State Examination (MMSE), Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) and Clinical Dementia Rating Scale Sum of Boxes (CDR-SB), the Lawton and Brody Physical Self-maintenance Scale (PSMS), and Activities of Daily Living Scale (ADL) were assessed using longitudinal mixed effects regression, adjusting for age, sex, education, and other relevant clinical characteristics.

RESULTS

Cohorts 1 (n = 287), 2 (n = 257), and 3 (n = 374) did not differ on age, race, APOE genotype, or cognitive and functional measures. Educational attainment increased over time (13.4, 14.1, and 14.5 years, respectively, p < 0.001). Anti-dementia drug use at baseline was less common in Cohort 1 (32.2% versus 65.0%, and 66.8%, p < 0.001). The rate of decline in MMSE and CDR-SB did not differ across cohorts. ADAS-Cog scores for Cohort 2 declined more slowly than Cohort 3 (Btime ×cohort2 = -0.91 ± 0.35, p = 0.009), whereas Cohort 1 did not differ from cohort 3 (reference). Cohorts 1 and 2 differed from Cohort 3 in progression rate on the PSMS, but not the IADL.

CONCLUSIONS

There were no consistent temporal trends in progression rates over time. Longitudinal data over 15-20 years may be confidently pooled for outcomes analysis, but unexplained variability in rate of decline on some measures may occur.

Genetic risk of dementia mitigated by cognitive reserve: A cohort study

OBJECTIVE

We investigated whether cognitive reserve modifies the risk of dementia attributable to apolipoprotein ε4 (APOE-ε4), a well-known genetic risk factor for dementia.

METHODS

We followed 2,556 cognitively intact participants aged ≥60 years from the ongoing prospective community-based Swedish National Study on Aging and Care in Kungsholmen (SNAC-K). Dementia was ascertained through clinical and neuropsychological assessments and diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, 4th edition criteria. Structural equation modeling was used to generate a cognitive reserve indicator from 4 previously validated contributors: early life education, midlife substantive work complexity, late life leisure activities, and late life social networks. Cox proportional hazard models estimated dementia risk in relation to cognitive reserve indicator. The interaction between the cognitive reserve indicator and APOE-ε4 was assessed on multiplicative and additive scales.

RESULTS

After an average of 6.3 years (range = 2.1-10.7) of follow-up, 232 dementia cases were ascertained. Relative to individuals in the lowest tertile of cognitive reserve indicator, those with moderate and high reserve were at a reduced risk of dementia. There was no multiplicative interaction between APOE-ε4 status and cognitive reserve indicator (p = 0.113). Additive interaction was statistically significant. Relative to APOE-ε4 carriers with low cognitive reserve, ε4 carriers with high reserve had a reduced risk of dementia (hazard ratio [HR] = 0.28, 95% confidence interval [CI] = 0.13-0.59). The magnitude of risk reduction was similar in ε4 noncarriers with a high cognitive reserve indicator (HR = 0.24, 95% CI = 0.15-0.40).

INTERPRETATION

Lifelong engagement in reserve-enhancing activities attenuates the risk of dementia attributable to APOE-ε4. Promoting cognitive reserve might be especially effective in subpopulations with high genetic risk of dementia. ANN NEUROL 2019.

A Cognitive Reserve and Social Support-Focused Latent Class Analysis to Predict Self-Reported Confusion or Memory Loss among Middle-Aged World Trade Center Health Registry Enrollees

The World Trade Center Health Registry includes 9/11 survivors who have been surveyed about their health conditions over time. The prevalence of posttraumatic stress disorder (PTSD) remains high among the cohort and is a risk factor for cognitive impairment or dementia. We thus sought to examine the degree to which confusion or memory loss (CML)—potential symptoms of cognitive decline—are occurring among enrollees aged 35–64 years. Cognitive reserve theory suggests that higher levels of education and engaging in cognitively challenging activities can create stronger neural connections, offering protection against cognitive decline. We hypothesized that enrollees with less cognitive reserve would be more likely to report CML. In this study, we: (1) estimated the incidence of CML in our study sample; (2) identified indicators of cognitive reserve (e.g., indicators of educational attainment, social support); and (3) determined whether CML is associated with cognitive reserve level, stratified by PSTD status. First, we described demographics of the study sample (n = 14,574) and probable PTSD status, also stratifying by CML. Next, we conducted a latent class analysis on two groups: those with probable PTSD and those without probable PTSD, creating classes with varying cognitive reserve levels. Finally, using adjusted log binomial models, we predicted risk of CML based on cognitive reserve level. The probable PTSD group (n = 1213) and not probable PTSD group (n = 13,252) each had four latent classes: low, medium-low, medium-high, and high cognitive reserve. In the probable PTSD model, compared to the high cognitive reserve class, those with medium-low cognitive reserve were 35% more likely to report CML (relative risk (RR) = 1.4, 95% confidence interval (CI): 1.1, 1.7). Among the not probable PTSD group, those with low and medium levels of cognitive reserve were significantly more likely to report CML (RR = 1.8 and 1.4, respectively). Overall, those with less cognitive reserve were more likely to report CML regardless of PTSD status.

Is There a Link Between Cognitive Reserve and Cognitive Function in the Oldest-Old?

Background

The oldest-old (aged ≥85 years) are the fastest growing age group, with the highest risk of cognitive impairment and dementia. This study investigated whether cognitive reserve applies to the oldest-old. This has implications for cognitive interventions in this age group.

Methods

Baseline and 5-year follow-up data from the Newcastle 85+ Study were used (N = 845, mean age = 85.5, 38% male). A Cognitive Reserve Index (CRI) was created, including: education, social class, marital status, engagement in mental activities, social participation, and physical activity. Global (Mini-Mental State Examination) and domain specific (Cognitive Drug Research Battery subtests assessing memory, attention, and speed) cognitive functions were assessed. Dementia diagnosis was determined by health records. Logistic regression analysis examined the association between CRI scores and incident dementia. Mixed effects models investigated baseline and longitudinal associations between the CRI scores and cognitive function. Analyses controlled for sex, age, depression, and cardiovascular disease history.

Results

Higher reserve associated with better cognitive performance on all baseline measures, but not 5-year rate of change. The CRI associated with prevalent, but not incident dementia.

Conclusions

In the oldest-old, higher reserve associated with better baseline global and domain-specific cognitive function and reduced risk of prevalent dementia; but not cognitive decline or incident dementia. Increasing reserve could promote cognitive function in the oldest-old. The results suggest there would be little impact on trajectories, but replication is needed. Development of preventative strategies would benefit from identifying the role of each factor in building reserve and why rate of change is not affected.

A Systematic Review for Functional Neuroimaging Studies of Cognitive Reserve Across the Cognitive Aging Spectrum

Objective

Cognitive reserve has been proposed to explain the discrepancy between clinical symptoms and the effects of aging or Alzheimer's pathology. Functional magnetic resonance imaging (fMRI) may help elucidate how neural reserve and compensation delay cognitive decline and identify brain regions associated with cognitive reserve. This systematic review evaluated neural correlates of cognitive reserve via fMRI (resting-state and task-related) studies across the cognitive aging spectrum (i.e., normal cognition, mild cognitive impairment, and Alzheimer's disease).

Method

This review examined published articles up to March 2017. There were 13 cross-sectional observational studies that met the inclusion criteria, including relevance to cognitive reserve, subjects 60 years or older with normal cognition, mild cognitive impairment, and/or Alzheimer's disease, at least one quantitative measure of cognitive reserve, and fMRI as the imaging modality. Quality assessment of included studies was conducted using the Newcastle-Ottawa Scale adapted for cross-sectional studies.

Results

Across the cognitive aging spectrum, medial temporal regions and an anterior or posterior cingulate cortex-seeded default mode network were associated with neural reserve. Frontal regions and the dorsal attentional network were related to neural compensation. Compared to neural reserve, neural compensation was more common in mild cognitive impairment and Alzheimer's disease.

Conclusions

Neural reserve and compensation both support cognitive reserve, with compensation more common in later stages of the cognitive aging spectrum. Longitudinal and intervention studies are needed to investigate changes between neural reserve and compensation during the transition between clinical stages, and to explore the causal relationship between cognitive reserve and potential neural substrates.

Translational research on reserve against neurodegenerative disease: consensus report of the International Conference on Cognitive Reserve in the Dementias and the Alzheimer's Association Reserve, Resilience and Protective Factors Professional Interest Area working groups

BACKGROUND

The concept of reserve was established to account for the observation that a given degree of neurodegenerative pathology may result in varying degrees of symptoms in different individuals. There is a large amount of evidence on epidemiological risk and protective factors for neurodegenerative diseases and dementia, yet the biological mechanisms that underpin the protective effects of certain lifestyle and physiological variables remain poorly understood, limiting the development of more effective preventive and treatment strategies. Additionally, different definitions and concepts of reserve exist, which hampers the coordination of research and comparison of results across studies.

DISCUSSION

This paper represents the consensus of a multidisciplinary group of experts from different areas of research related to reserve, including clinical, epidemiological and basic sciences. The consensus was developed during meetings of the working groups of the first International Conference on Cognitive Reserve in the Dementias (24-25 November 2017, Munich, Germany) and the Alzheimer's Association Reserve and Resilience Professional Interest Area (25 July 2018, Chicago, USA). The main objective of the present paper is to develop a translational perspective on putative mechanisms underlying reserve against neurodegenerative disease, combining evidence from epidemiological and clinical studies with knowledge from animal and basic research. The potential brain functional and structural basis of reserve in Alzheimer's disease and other brain disorders are discussed, as well as relevant lifestyle and genetic factors assessed in both humans and animal models.

CONCLUSION

There is an urgent need to advance our concept of reserve from a hypothetical model to a more concrete approach that can be used to improve the development of effective interventions aimed at preventing dementia. Our group recommends agreement on a common dictionary of terms referring to different aspects of reserve, the improvement of opportunities for data sharing across individual cohorts, harmonising research approaches across laboratories and groups to reduce heterogeneity associated with human data, global coordination of clinical trials to more effectively explore whether reducing epidemiological risk factors leads to a reduced burden of neurodegenerative diseases in the population, and an increase in our understanding of the appropriateness of animal models for reserve research.

Cognitive Performance among Cognitively Healthy Adults Aged 30-100 Years

Background/Aims

To detect cognitive decline in older adults, measures of verbal fluency and verbal memory are widely used. Less is known about performance in these measures in younger persons or according to education level and gender. We investigated cognitive performance according to age, education and gender among cognitively healthy adults aged 30–100 years.

Methods

The study population comprised 4,174 cognitively healthy persons participating in the nationally representative Finnish Health 2011 survey. Cognitive assessment included verbal fluency, word list memory, word list recall and word list savings from the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological battery.

Results

Total variance in the cognitive test performance explained by age, education and gender varied from 12.3 to 31.2%. A decreasing trend in cognitive performance existed in all subtests by advancing age, with differences appearing between 50 and 55 years. Persons with the highest-education level performed best for all measures. For the participants < 55 years, education explained part of the variance, while age and gender did not.

Conclusions

When assessing cognition, age and education should be accounted for in more detail in research and clinical practice. Additionally, the cohort effect and its potential impact on the renewal cycle of future normative values for cognitive tests should be considered.

A Brief Review of Paradigm Shifts in Prevention of Alzheimer's Disease: From Cognitive Reserve to Precision Medicine

Alzheimer's disease (AD) and related dementias can be an enormous economic burden for taxpayers, patients, their families, medical systems, and society as a whole. Since disease-modifying treatments have failed, several studies have instead focused on a paradigm shift for preventing and treating AD. A higher cognitive reserve (e.g., greater education, occupational attainment, or more leisure activities) is associated with protection against disease-related cognitive decline. Precision medicine aims to optimize the effectiveness of disease prevention and treatment by considering specific biological components of individuals. We suggest that research into cognitive reserve and precision medicine could be a key to overcoming the limitations of traditional approaches to the prevention and treatment of AD.

Cognitive reserve

Cognitive reserve is a latent construct theorized to account for the discrepancy between observed brain deterioration and ultimate clinical outcomes. This review outlines the theoretical development of the reserve concept and presents major trends within epidemiological and neuroimaging research literatures in support of such a construct. Particular focus is placed on the implications for cognitive aging and dementia.

Educational Attainment Moderates the Association Between Hippocampal Volumes and Memory Performances in Healthy Older Adults

Objective: To examine whether educational attainment, as a proxy of cognitive reserve, moderated the association between hippocampal volumes and episodic verbal memory performances in healthy older adults.

Methods: Data from 76 community dwelling older adults were included in the present study. Measures of hippocampal volumes (total, left, and right) were obtained using FreeSurfer software. Immediate and delayed verbal recall scores were derived from performances on the California Verbal Learning Test-Second Edition and the Wechsler Memory Scale- Third Edition. Educational attainment was defined by years of education. Linear regression analyses were performed using immediate and delayed recall as dependent variables and hippocampal volumes, years of education, and their interaction terms as independent variables. All analyses were controlled for age, sex, depression, and health status.

Results: Total and left Hippocampal volumes had a positive main effect on delayed recall only. Additionally, the interaction between total, left, and right hippocampal volumes and education was a significant predictor for delayed recall performance but not for immediate recall performance. The positive association between hippocampal volumes and delayed recall was greatest in those with more years of education.

Conclusion: Larger hippocampal volumes were associated with better delayed verbal recall and the effect on delayed recall was greatest in those with more years of education. Having higher levels of education, or cognitive reserve, may enable individuals to capitalize on greater structural integrity in the hippocampus to support delayed recall in old age. However, longitudinal research is needed to investigate the directionality of these associations.

Life-course determinants of cognitive reserve (CR) in cognitive aging and dementia - a systematic literature review

OBJECTIVES

The concept of cognitive reserve (CR) is defined as a moderator, which allows an individual to preserve cognition despite underlying brain pathology. There is no consensus of what potentially modifiable CR determinants are of greatest importance. The aim of this review was to identify life-course factors which protect older individuals from expressing cognitive decline despite the presence of brain pathology.

METHOD

A systematic review search was performed in MEDLINE (1946-06/09/13), EMBASE (1947-06/09/13), and PsycheInfo (1967-06/09/13). We included studies examining CR in the context of the four commonest subtypes of dementia, mild cognitive impairment or healthy aging. Studies which combined measurement of underlying dementia-related neuropathology, cognitive function, and factors providing CR in a single model were accepted. We performed a qualitative synthesis of the results.

RESULTS

Thirty-four studies out of 9229 screened records met our inclusion criteria and were therefore quality assessed and data extracted. Variation in CR definition made comparison across studies difficult. One hundred and forty-four out of 156 models examined education and occupation: overall, 58% of eligible models classified education and 60% occupation as a CR determinant, with 12% and 44% of those, respectively, being of high quality. Within healthy population suitable to inform preventative interventions, there was consistent evidence for education having a protective effect on general cognition in the face of multiple brain burden measures, while occupation presented inconclusive results within cognitive groups.

CONCLUSIONS

Further research on modifiable determinants of CR beyond education/occupation including early-life factors and consensus on CR definition are warranted.

Negative symptoms of psychosis: A life course approach and implications for prevention and treatment

AIM

Negative symptoms are a cause of enduring disability in serious mental illness. In spite of this, the development of effective treatments for negative symptoms has remained slow. The challenge of improving negative symptom outcomes is compounded by our limited understanding of their aetiology and longitudinal development.

METHODS

A literature search was conducted for life course approach of negative symptoms using PubMed. Further articles were included following manual checking of reference lists and other search strategies. The paper contains a theoretical synthesis of the literature, summarized using conceptual models.

RESULTS

Negative symptom definitions are compared and considered within a context of the life course. Previous studies suggest that several illness phases may contribute to negative symptoms, highlighting our uncertainty in relation to the origin of negative symptoms.

CONCLUSIONS

Similar to other aspects of schizophrenia, negative symptoms likely involve a complex interplay of several risk and protective factors at different life phases. Concepts suggested in this article, such as "negative symptom reserve" theory, require further research, which may inform future prevention and treatment strategies.

Cognitive reserve as a moderator of the negative association between mood and cognition: evidence from a population-representative cohort

BACKGROUND

Cognitive reserve (CR) has been associated with better cognitive function and lower risk of depression in older people, yet it remains unclear whether CR moderates the association between mood and cognition. This study aimed to investigate whether a comprehensive indicator of CR, including education, occupation and engagement in cognitive and social activities, acts as a moderator of this association.

METHODS

This was a cross-sectional study utilising baseline data from the Cognitive Function and Ageing Study II (CFAS II), a large population-based cohort of people aged 65+ in England. Complete data on the measures of CR, mood and cognition were available for 6565 dementia-free individuals. Linear regression models were used to investigate the potential modifying effect of CR on the association between cognition and mood with adjustment for age, sex and missing data.

RESULTS

Levels of CR did moderate the negative association between mood and cognition; the difference in cognition between those with and without a clinical level mood disorder was significantly smaller in the middle (-2.28; 95% confidence interval (CI) -3.65 to -0.90) and higher (-1.30; 95% CI -2.46 to -0.15) CR groups compared with the lower CR group (-4.01; 95% CI -5.53 to -2.49). The individual components of CR did not significantly moderate the negative association between mood and cognition.

CONCLUSION

These results demonstrate that CR, indexed by a composite score based on multiple indicators, can moderate the negative association between lowered mood and cognition, emphasising the importance of continuing to build CR across the lifespan in order to maintain cognitive health.

The Cognitive Reserve Model in the Development of Delirium: The Successful Aging After Elective Surgery Study

We evaluated the role of cognitive and brain reserve markers in modifying the risk of postoperative delirium associated with a pathophysiologic marker. The Successful Aging after Elective Surgery study (SAGES) enrolled 556 adults age ≥70 years without dementia scheduled for major surgery. Patients were assessed preoperatively and daily during hospitalization for delirium. We used C-reactive protein (CRP) as a pathophysiologic marker of inflammation, previously associated with delirium. Markers of reserve included vocabulary knowledge, education, cognitive activities, occupation type and complexity, head circumference, intracranial volume, and leisure activities. Vocabulary knowledge, cognitive activities, and education significantly modified the association of CRP and postoperative delirium ( P < .01). However, effect sizes-when statistically significant-were small in magnitude. The strongest effect modification was observed for vocabulary knowledge: high scores were generally protective but not at high levels of CRP. Select reserve markers attenuate the risk of delirium associated with lower grade inflammatory processes, supporting the role of reserve in delirium.

Static and Dynamic Cognitive Reserve Proxy Measures: Interactions with Alzheimer's Disease Neuropathology and Cognition

Objective

Years of education are the most common proxy for measuring cognitive reserve (CR) when assessing the relationship between Alzheimer’s disease (AD) neuropathology and cognition. However, years of education may be limited as a CR proxy given that it represents a specific timeframe in early life and is static. Studies suggest that measures of intellectual function provide a dynamic estimate of CR that is superior to years of education since it captures the effect of continued learning over time. The present study determined whether dynamic measures of CR were better predictors of episodic memory and executive function in the presence of AD pathology than a static measure of CR.

Methods

Subjects examined died with a pre-mortem clinical diagnosis of no cognitive impaired, mild cognitive impairment and mild to moderate AD. CERAD and Braak stage were used to stratify the sample by AD pathology severity. Linear regression analyses using CR by CERAD and CR by Braak stage interaction terms were used to determine whether Extended Range Vocabulary Test (ERVT) scores or years of education were significantly associated with episodic memory composite (EMC) and executive function composite (EFC) performance. All models were adjusted for clinical diagnosis, age at death, gender, APOE e4 carrier status and Braak stage.

Results

For episodic memory, years of education by CERAD interaction were not statistically significant (β=-0.01, SE=0.01, p=0.53). By contrast, ERVT interaction with CERAD diagnosis was statistically significant (β=-0.03, SE=0.01, p=0.004). Among the models using Braak stages, none of the CR by pathology interactions were associated with EMC or EFC.

Conclusion

Results suggest that a dynamic rather than a static measure is a better indicator of CR and that the relationship between CR and cognition is dependent upon the severity of select AD criteria.

What is the Relationship of Traumatic Brain Injury to Dementia?

There is a long history linking traumatic brain injury (TBI) with the development of dementia. Despite significant reservations, such as recall bias or concluding causality for TBI, a summary of recent research points to several conclusions on the TBI-dementia relationship. 1) Increasing severity of a single moderate-to-severe TBI increases the risk of subsequent Alzheimer's disease (AD), the most common type of dementia. 2) Repetitive, often subconcussive, mild TBIs increases the risk for chronic traumatic encephalopathy (CTE), a degenerative neuropathology. 3) TBI may be a risk factor for other neurodegenerative disorders that can be associated with dementia. 4) TBI appears to lower the age of onset of TBI-related neurocognitive syndromes, potentially adding "TBI cognitive-behavioral features". The literature further indicates several specific risk factors for TBI-associated dementia: 5) any blast or blunt physical force to the head as long as there is violent head displacement; 6) decreased cognitive and/or neuronal reserve and the related variable of older age at TBI; and 7) the presence of apolipoprotein E ɛ4 alleles, a genetic risk factor for AD. Finally, there are neuropathological features relating TBI with neurocognitive syndromes: 8) acute TBI results in amyloid pathology and other neurodegenerative proteinopathies; 9) CTE shares features with neurodegenerative dementias; and 10) TBI results in white matter tract and neural network disruptions. Although further research is needed, these ten findings suggest that dose-dependent effects of violent head displacement in vulnerable brains predispose to dementia; among several potential mechanisms is the propagation of abnormal proteins along damaged white matter networks.

Cognitive performance in healthy older adults relates to spontaneous switching between states of functional connectivity during rest

Growing evidence has shown that brain activity at rest slowly wanders through a repertoire of different states, where whole-brain functional connectivity (FC) temporarily settles into distinct FC patterns. Nevertheless, the functional role of resting-state activity remains unclear. Here, we investigate how the switching behavior of resting-state FC relates with cognitive performance in healthy older adults. We analyse resting-state fMRI data from 98 healthy adults previously categorized as being among the best or among the worst performers in a cohort study of >1000 subjects aged 50+ who underwent neuropsychological assessment. We use a novel approach focusing on the dominant FC pattern captured by the leading eigenvector of dynamic FC matrices. Recurrent FC patterns - or states - are detected and characterized in terms of lifetime, probability of occurrence and switching profiles. We find that poorer cognitive performance is associated with weaker FC temporal similarity together with altered switching between FC states. These results provide new evidence linking the switching dynamics of FC during rest with cognitive performance in later life, reinforcing the functional role of resting-state activity for effective cognitive processing.

Positive impacts of early auditory training on cortical processing at an older age

Progressive negative behavioral changes in normal aging are paralleled by a complex series of physical and functional declines expressed in the cerebral cortex. In studies conducted in the auditory domain, these degrading physical and functional cortical changes have been shown to be broadly reversed by intensive progressive training that improves the spectral and temporal resolution of acoustic inputs and suppresses behavioral distractors. Here we found older rats that were intensively trained on an attentionally demanding modulation-rate recognition task in young adulthood substantially retained training-driven improvements in temporal rate discrimination abilities over a subsequent 18-mo epoch-that is, forward into their older age. In parallel, this young-adult auditory training enduringly enhanced temporal and spectral information processing in their primary auditory cortices (A1). Substantially greater numbers of parvalbumin- and somatostatin-labeled inhibitory neurons (closer to the numbers recorded in young vigorous adults) were recorded in the A1 and hippocampus in old trained versus untrained age-matched rats. These results show that a simple form of training in young adulthood in this rat model enduringly delays the otherwise expected deterioration of the physical status and functional operations of the auditory nervous system, with evident training impacts generalized to the hippocampus.

Cognitive reserve and self-efficacy as moderators of the relationship between stress exposure and executive functioning among spousal dementia caregivers

BACKGROUND

A substantial literature has reported that stress negatively impacts on cognitive processes. As dementia caregiving can be stressful, it has been hypothesized that the challenges of dementia care may increase caregivers' own vulnerability to cognitive decline. Prefrontal processes are thought to be most vulnerable to stress; however, few studies have examined whether greater caregiver stress predicts poorer executive dysfunction, and no previous research has considered potential moderators of this relationship. We examined (1) whether greater psychological stress mediated a relationship between caregiver stress exposure and executive functioning and (2) whether greater self-efficacy and cognitive reserve (CR) moderated this relationship.

METHOD

Spousal dementia caregivers (n = 253) completed the Neuropsychiatric Inventory Questionnaire (stress exposure), the Perceived Stress Scale, the National Adult Reading Test (CR), the Fortinsky dementia-specific caregiver self-efficacy scale, and the Color Trails Test (executive functioning). Moderated mediation was tested using the PROCESS macro. Age, gender, and dementia risk factors were included as covariates.

RESULTS

Greater stress exposure indirectly predicted executive functioning through psychological stress. Stronger relationships between greater psychological stress and poorer executive functioning were observed among caregivers with lower CR; there was no evidence that self-efficacy moderated the relationship between stress exposure and psychological stress.

CONCLUSIONS

Our findings are in line with the idea that greater psychological stress in response to challenges associated with dementia care predicts poorer caregiver executive functioning, particularly among caregivers with low CR. However, these findings are cross sectional; it is also possible that poorer executive functioning contributes to greater caregiver stress.

Effect of Formal Education on Vascular Cognitive Impairment after Stroke: A Meta-analysis and Study in Young-Stroke Patients

OBJECTIVES

The extent of vascular cognitive impairment (VCI) after stroke varies greatly across individuals, even when the same amount of brain damage is present. Education level is a potentially protective factor explaining these differences, but results on its effects on VCI are inconclusive.

METHODS

First, we performed a meta-analysis on formal education and VCI, identifying 21 studies (N=7770). Second, we examined the effect of formal education on VCI in young-stroke patients who were cognitively assessed on average 11.0 (SD=8.2) years post-stroke (the FUTURE study cohort). The total sample consisted of 277 young-stroke patients with a mean age at follow-up 50.9 (SD=10.3). Age and education-adjusted expected scores were computed using 146 matched stroke-free controls.

RESULTS

The meta-analysis showed an overall effect size (z') of 0.25 (95% confidence interval [0.18-0.31]), indicating that formal education level had a small to medium effect on VCI. Analyses of the FUTURE data showed that the effect of education on post-stroke executive dysfunction was mediated by age (β age -0.015; p<.05). Below-average performance in the attention domain was more frequent for low-education patients (χ2(2)=9.8; p<.05).

CONCLUSIONS

While education level was found to be related to post-stroke VCI in previous research, the effects were small. Further analysis in a large stroke cohort showed that these education effects were fully mediated by age, even in relatively young stroke patients. Education level in and of itself does not appear to be a valid indicator of cognitive reserve. Multi-indicator methods may be more valid, but have not been studied in relation to VCI. (JINS, 2017, 23, 223-238).

A Mediterranean Diet to Improve Cardiovascular and Cognitive Health: Protocol for a Randomised Controlled Intervention Study

The Mediterranean diet has demonstrated efficacy for improving cardiovascular and cognitive health. However, a traditional Mediterranean diet delivers fewer serves of dairy and less dietary calcium than is currently recommended in Australia, which may limit long-term sustainability. The present study aims to evaluate whether a Mediterranean diet with adequate dairy and calcium can improve cardiovascular and cognitive function in an at-risk population, and thereby reduce risk of cardiovascular disease (CVD) and cognitive decline. A randomised, controlled, parallel, crossover design trial will compare a Mediterranean diet supplemented with dairy foods against a low-fat control diet. Forty participants with systolic blood pressure above 120 mmHg and at least two other risk factors of CVD will undertake each dietary intervention for eight weeks, with an eight-week washout period between interventions. Systolic blood pressure will be the primary measure of interest. Secondary outcomes will include measures of cardiometabolic health, dietary compliance, cognitive function, assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB), psychological well-being and dementia risk. This research will provide empirical evidence as to whether the Mediterranean diet can be modified to provide recommended dairy and calcium intakes while continuing to deliver positive effects for cardiovascular and cognitive health. The findings will hold relevance for the field of preventative healthcare and may contribute to revisions of national dietary guidelines.

Cognitive Reserve as a Modifier of Clinical Expression in Chronic Traumatic Encephalopathy: A Preliminary Examination

This study conducted a preliminary examination on cognitive reserve (CR) as a modifier of symptom expression in subjects with autopsy-confirmed chronic traumatic encephalopathy (CTE). The sample included 25 former professional football players neuropathologically diagnosed with CTE stage III or IV. Next of kin interviews ascertained age at cognitive and behavioral/mood symptom onset and demographic/athletic characteristics. Years of education and occupational attainment defined CR. High occupational achievement predicted later age at cognitive (p=0.02) and behavioral/mood (p=0.02) onset. Education was not an individual predictor. These preliminary findings suggest that CR may forestall the clinical manifestation of CTE.

Cognitive reserve lessens the burden of white matter lesions on executive functions in bipolar disorder

BACKGROUND

The concept of cognitive reserve (CR) hypothesizes that intellectually stimulating activities provide resilience against brain pathology/disease. Whereas brain abnormalities and cognitive impairment are frequently reported in bipolar disorder (BD), it is unknown whether the impact of brain alterations can be lessened by higher CR in BD.

METHOD

We tested if higher CR would reduce the influence of total volumes of deep white matter hypointensities (WMH), ventricular cerebrospinal fluid (CSF), and prefrontal cortex on memory, executive, and attention/speed functions in patients with BD (n = 75). Linear regression models with interaction terms for CR and brain volumes were applied to directly test if CR reduces the influence of brain pathology on cognitive domains.

RESULTS

CR reduced the influence of total volumes of deep WMH (β = -0.38, Q = 0.003) and ventricular CSF (β = -41, Q = 006) on executive functions.

CONCLUSIONS

The interactions between CR and total volumes of deep WMH/ventricular CSF appear to account for executive functioning in BD. The results suggest that the concept of CR is applicable in BD. Higher reserve capacity in BD alters the relationship between brain pathology and clinical presentation.

Preoperative Cognitive Performance Dominates Risk for Delirium Among Older Adults

BACKGROUND

Cognitive impairment is a well-recognized risk factor for delirium. Our goal was to determine whether the level of cognitive performance across the nondemented cognitive ability spectrum is correlated with delirium risk and to gauge the importance of cognition relative to other known risk factors for delirium.

METHODS

The Successful Aging after Elective Surgery study enrolled 566 adults aged ≥70 years scheduled for major surgery. Patients were assessed preoperatively and daily during hospitalization for the occurrence of delirium using the Confusion Assessment Method. Cognitive function was assessed preoperatively with an 11-test neuropsychological battery combined into a composite score for general cognitive performance (GCP). We examined the risk for delirium attributable to GCP, as well as demographic factors, vocabulary ability, and informant-rated cognitive decline, and compared the strength of association with risk factors identified in a previously published delirium prediction rule for delirium.

RESULTS

Delirium occurred in 135 (24%) patients. Lower GCP score was strongly and linearly predictive of delirium risk (relative risk = 2.0 per each half standard deviation difference in GCP score, 95% confidence interval, 1.5-2.5). This effect was not attenuated by statistical adjustment for demographics, vocabulary ability, and informant-rated cognitive decline. The effect was stronger than, and largely independent from, both standard delirium risk factors and comorbidity.

CONCLUSION

Risk of delirium is linearly and strongly related to presurgical cognitive performance level even at levels above the population median, which would be considered unimpaired.

Cognitive Reserve in Healthy Aging and Alzheimer's Disease: A Meta-Analysis of fMRI Studies

Cognitive reserve (CR) has been defined as the ability to optimize or maximize performance through differential recruitment of brain networks. In the present study, we aimed at providing evidence for a consistent brain network underpinning CR in healthy and pathological aging. To pursue this aim, we performed a coordinate-based meta-analysis of 17 functional magnetic resonance imaging studies on CR proxies in healthy aging, Alzheimer's disease (AD), and mild cognitive impairment (MCI). We found that different brain areas were associated with CR proxies in healthy and pathological aging. A wide network of areas, including medial and lateral frontal areas, that is, anterior cingulate cortex and dorsolateral prefrontal cortex, as well as precuneus, was associated with proxies of CR in healthy elderly patients. The CR proxies in patients with AD and amnesic-MCI were associated with activation in the anterior cingulate cortex. These results were discussed hypothesizing the existence of possible compensatory mechanisms in healthy and pathological aging.

Higher Education Is Associated with a Lower Risk of Dementia after a Stroke or TIA. The Rotterdam Study

BACKGROUND

Higher education is associated with a lower risk of dementia, possibly because of a higher tolerance to subclinical neurodegenerative pathology. Whether higher education also protects against dementia after clinical stroke or transient ischemic attack (TIA) remains unknown.

METHODS

Within the population-based Rotterdam Study, 12,561 participants free of stroke, TIA and dementia were followed for occurrence of stroke, TIA and dementia. Across the levels of education, associations of incident stroke or TIA with subsequent development of dementia and differences in cognitive decline following stroke or TIA were investigated.

RESULTS

During 124,862 person-years, 1,463 persons suffered a stroke or TIA, 1,158 persons developed dementia, of whom 186 developed dementia after stroke or TIA. Risk of dementia after a stroke or TIA, compared to no stroke or TIA, was highest in the low education category (hazards ratio [HR] 1.46, 95% CI 1.18-1.81) followed by intermediate education category (HR 1.36, 95% CI 1.03-1.81). No significant association was observed in the high education category (HR 0.62, 95% CI 0.25-1.54). In gender stratified analyses, decrease in risk of dementia with increasing education was significant only in men.

CONCLUSION

Higher education is associated with a lower risk of dementia after stroke or TIA, particularly in men, which might be explained by a higher cognitive reserve.

Usefulness of data from magnetic resonance imaging to improve prediction of dementia: population based cohort study

OBJECTIVE

To determine whether the addition of data derived from magnetic resonance imaging (MRI) of the brain to a model incorporating conventional risk variables improves prediction of dementia over 10 years of follow-up.

DESIGN

Population based cohort study of individuals aged ≥ 65.

SETTING

The Dijon magnetic resonance imaging study cohort from the Three-City Study, France.

PARTICIPANTS

1721 people without dementia who underwent an MRI scan at baseline and with known dementia status over 10 years' follow-up.

MAIN OUTCOME MEASURE

Incident dementia (all cause and Alzheimer's disease).

RESULTS

During 10 years of follow-up, there were 119 confirmed cases of dementia, 84 of which were Alzheimer's disease. The conventional risk model incorporated age, sex, education, cognition, physical function, lifestyle (smoking, alcohol use), health (cardiovascular disease, diabetes, systolic blood pressure), and the apolipoprotein genotype (C statistic for discrimination performance was 0.77, 95% confidence interval 0.71 to 0.82). No significant differences were observed in the discrimination performance of the conventional risk model compared with models incorporating data from MRI including white matter lesion volume (C statistic 0.77, 95% confidence interval 0.72 to 0.82; P=0.48 for difference of C statistics), brain volume (0.77, 0.72 to 0.82; P=0.60), hippocampal volume (0.79, 0.74 to 0.84; P=0.07), or all three variables combined (0.79, 0.75 to 0.84; P=0.05). Inclusion of hippocampal volume or all three MRI variables combined in the conventional model did, however, lead to significant improvement in reclassification measured by using the integrated discrimination improvement index (P=0.03 and P=0.04) and showed increased net benefit in decision curve analysis. Similar results were observed when the outcome was restricted to Alzheimer's disease.

CONCLUSIONS

Data from MRI do not significantly improve discrimination performance in prediction of all cause dementia beyond a model incorporating demographic, cognitive, health, lifestyle, physical function, and genetic data. There were, however, statistical improvements in reclassification, prognostic separation, and some evidence of clinical utility.