Rate of memory decline in AD is related to education and occupation: cognitive reserve?

Cognitive reserve in individuals with frontotemporal dementia: a systematic review

As the literature related to cognitive reserve (CR) in individuals with frontotemporal dementia (FTD) is only emerging, a clear consensus on the relationship among CR proxies, brain status, and clinical performance has not been reached. The primary aim of this systematic review was to examine the relationship among sociobehavioral proxies of CR, brain status, and clinical performance in individuals with various types of FTD. Additionally, characteristics of patient population, sociobehavioral proxies, disease severity tools, and brain status measures used were identified. The systematic review was conducted using comprehensive search terms in Medline, PsychINFO, PubMed, and Web of Science. Eligibility criteria were for studies to include at least one CR and one brain status measure for individuals with FTD, be published in a peer-reviewed journal, and be published in English. The Newcastle-Ottawa Quality Assessment Scale was used to assess study quality and bias risk. A total of 237 titles and abstracts were screened, with 13 studies meeting inclusion criteria. Together, these studies report 1,423 participants with FTD. Based on the included studies, partial support was demonstrated for CR in individuals with FTD when education, occupation, and leisure were utilized as CR proxies. The variability in results among studies could be related to the different tools used to measure CR, brain status, and disease severity. This review provides recommendations for future studies: incorporating longitudinal designs, in depth neuropsychological testing, consistent disease duration measure, and transparant statistical output reporting.

Change of leisure activity participation and associations with cognitive frailty in older adults: A population-based longitudinal study

OBJECTIVES

To examine changes in leisure activity participation and their associations with cognitive frailty among older adults.

METHODS

The study utilized data from the Chinese Longitudinal Healthy Longevity Survey covering 2008-2018. Three distinct intervals represented short-term (2008-2011), medium-term (2008-2014) and long-term (2008-2018) changes in leisure activity participation, and the change patterns of levels of leisure activities based on the tertile were described. Restricted cubic splines (RCS) were used to determine the inflection point of the absolute value of leisure activity participation over two time points. Group-based trajectory modeling identified trajectories of leisure activity participation among participants from 2008 to 2018. Logistic regression analysis examined how changes in leisure activity participation impacted cognitive frailty.

RESULTS

Five patterns of change in leisure activity participation were identified, including the persistently low group, the declining (medium-low, high-low, high-medium) group, persistently medium, rising (low-medium, low-high, medium-high), and persistently high levels of activity. A lower risk of cognitive frailty was found among three groups of persistently medium, rising, and persistently high levels of activity across three distinct intervals and among the declining group over the short-term and long-term intervals but not in the medium-term interval than among the persistently low group, respectively. RCS analysis showed that the inflection point of the association between absolute changes in leisure activity and cognitive frailty was -2.11 (short-term), -0.9 (medium-term), and -3.94 (long-term). Leisure activity trajectories were categorized into persistently low, persistently moderate, and persistently high groups, and both the persistently moderate and persistently high groups exhibited a lower risk of cognitive frailty compared to the persistently low group.

CONCLUSION

Persistently moderate to high levels and increasing levels of leisure activities can reduce the risk of cognitive frailty in the short, medium, and long term, and even the declining in leisure activity participation less than the threshold could protect against cognitive frailty, particularly in the short and long term.

Resistance and resilience to tau pathology in Alzheimer's disease: Effects of age, sex, and APOE alleles

INTRODUCTION

Neurofibrillary tangles (NFTs), a hallmark of tau pathology in Alzheimer's disease (AD), accumulate in the aging brain. However, some individuals remain cognitively intact despite high Braak (III-VI) stages, which characterize NFTs' accumulation.

METHODS

We studied resistance and resilience to tau pathology by assessing Braak stages based on apolipoprotein E (APOE) alleles, sex, and age in a sample of 1932 cognitively intact individuals of European ancestry from the Alzheimer's Disease Sequencing Project (ADSP).

RESULTS

Resistance, characterized by low (0-II) Braak stages, was observed in men and women younger than 85 years of age. Resilience, indicated by high (III-VI) Braak stages, increased significantly with age in both men and women for each APOE allele. It became more pronounced, with the proportion of high Braak stages exceeding 50% at 85 years and older in women, irrespective of the APOE allele.

DISCUSSION

The identification of factors underlying resistance and resilience against AD-related pathologies is essential for promoting cognitively healthy aging.

Highlights

We investigated cognitive resistance and resilience to tau pathology in Alzheimer's disease (AD).This study included individuals who were not diagnosed with AD.Braak stages 0-II and III-VI were considered as a measure of resistance and resilience, respectively.Resistance was stronger at ages younger than 85 years in non-carriers of the apolipoprotein E (APOE) ε4 allele.Resilience increased with age for each APOE allele independently of sex.At age 85 years and older, high resilience (>50%) was observed in women regardless of the APOE allele.

Individualized and Biomarker-Based Prognosis of Longitudinal Cognitive Decline in Early Symptomatic Alzheimer's Disease

Background

Although individualized models using demographic, MRI, and biological markers have recently been applied in mild cognitive impairment (MCI), a similar study is lacking for patients with early Alzheimer's disease (AD) with biomarker evidence of abnormal amyloid in the brain.

Objective

We aimed to develop prognostic models for individualized prediction of cognitive change in early AD.

Methods

A total of 421 individuals with early AD (MCI or mild dementia due to AD) having biomarker evidence of abnormal amyloid in the brain were included in the current study. The primary cognitive outcome was the slope of change in Alzheimer's Disease Assessment Scale-cognitive subscale-13 (ADAS-Cog-13) over a period of up to 5 years.

Results

A model combining demographics, baseline cognition, neurodegenerative markers, and CSF AD biomarkers provided the best predictive performance, achieving an overfitting-corrected R2 of 0.59 (bootstrapping validation). A nomogram was created to enable clinicians or trialists to easily and visually estimate the individualized magnitude of cognitive change in the context of patient characteristics. Simulated clinical trials suggested that the inclusion of our nomogram into the enrichment strategy would lead to a substantial reduction of sample size in a trial of early AD.

Conclusions

Our findings may be of great clinical relevance to identify individuals with early AD who are likely to experience fast cognitive deterioration in clinical practice and in clinical trials.

Exploring transfer effects on memory and its neural mechanisms through a computerized cognitive training in mild cognitive impairment: randomized controlled trial

BACKGROUND

Computerized cognitive training (CCT) has been proposed as a potential therapy for cognitive decline. One of the benefits of CCT is a transfer effect, but its mechanism on the memory domain is unclear. This study aimed to investigate the transfer effect of non-memory multidomain CCT on the memory domain and its neural basis in patients with mild cognitive impairment (MCI) through a randomized controlled trial.

METHODS

Patients with MCI recruited from memory clinics were randomly assigned to either the CCT or the control group. The CCT group received multidomain CCT training excluding memory training, while the control group read educational books with learning-based quizzes twice a week for 8 weeks. Participants underwent memory tests yielding a composite score, other cognitive domain tests, non-cognitive scales, and resting-state functional magnetic resonance imaging (rsfMRI), at baseline and after intervention. Within- and between-group comparisons, group × time interactions, and seed-to-voxel analyses in memory-involving brain networks were performed.

RESULTS

The CCT group showed improvement over the control group in memory domain (Group × time, F = 5.87, P = 0.03, η2 = 0.31), which was related with the increased connectivity in the hippocampal-frontal and fusiform-occipital network. No other cognitive and non-cognitive symptoms differed between groups after adjusting for covariates.

CONCLUSION

Eight weeks of multidomain CCT without memory training improved memory function and restored functional network in the hippocampal and medial temporal region in MCI patients. These results can provide evidence for the transferring ability of CCT on memory functioning with its neural basis.

The complex interplay between cognitive reserve, age of diagnosis and cognitive decline in Alzheimer's disease: a retrospective study

OBJECTIVE

The present study examined the cognitive reserve (CR) theory at late stages of Alzheimer's disease (AD). The objective is to replicate previous studies and examine the complex role of education and family size as indicators of CR.

PARTICIPANTS AND METHODS

This is a retrospective study included 642 patients diagnosed with AD after age 65, categorized into low education (LE, ≤ 8 years, n = 141) and medium-high education (MHE, ≥ 9 years, n = 442) groups. Participants were followed up longitudinally using the Mini Mental State Examination.

RESULTS

Higher education in the MHE group, but not in the LE group, correlated with delayed diagnosis. In both groups, higher education correlated with accelerated cognitive decline. In the MHE group, country of origin was associated with cognitive decline, while in the LE group, it was linked to family size.

CONCLUSIONS

This study shows that in patients with MHE but not in LE, higher education resulted in delayed diagnosis. Conversely, in cases of LE, this measure may not fully reflect CR and abilities. Additionally, higher education was associated with faster deterioration, a finding that has not been replicated often in the literature. The study illustrates the complex impact of CR proxies on age of diagnosis and cognitive decline.

The Paradox in Positive and Negative Aspects of Emotional Functioning Among Older Adults with Early Stages of Cognitive Impairment

Introduction: Emotional functioning in older adults is influenced by normal aging and cognitive impairment, likely heterogeneous across positive versus negative aspects of emotional functioning. Little is known about positive emotional experiences at the early stages of cognitive impairment. Methods: We assessed different aspects of emotional functioning among 448 participants aged 65+ (Normal Control (NC) = 276, Mild Cognitive Impairment (MCI) = 103, and mild dementia of the Alzheimer type (mild DAT) = 69) and tested moderators. Results: Compared to NC, older adults with MCI and mild DAT have maintained many positive aspects of emotional functioning, despite higher levels of negative affect, sadness, and loneliness. Among the oldest-old, the mild DAT group experienced higher fear and lower self-efficacy. Discussion: Older adults at early stages of cognitive impairment can experience positive aspects of emotional functioning, such as positive affect, purpose, and life satisfaction, all of which are important buildable psychological resources for coping.

Cognitive reserve modulates mental health in adulthood

Cognitive Reserve (CR) reflects acquired knowledge, skills, and abilities throughout life, and it is known for modulating cognitive efficiency in healthy and clinical populations. CR, which was initially proposed to explain individual differences in the clinical presentation of dementia, has subsequently been extended to healthy ageing, showing its role in cognitive efficiency also during middle age. Recently, CR has been linked to affective processes in psychiatric conditions such as schizophrenia, major depressive and anxiety symptoms, and psychological distress, suggesting its potential role in emotional expression and regulation. Whether the role of CR in mental health extends to non-pathological adults, and whether this is only relevant in older age is not yet clear. The aim of this work was therefore to explore the relationship between CR and mental health in healthy adults, with a focus on middle adulthood (40-60). In a sample of 96 participants, we found a positive association between CR and mental health outcomes, such that a higher cognitive reserve index corresponded to fewer mental health reported symptoms. Specifically, a higher CR reflecting professional activities was associated with lower stress levels, especially in middle agers. Taken together, these data therefore suggest that engaging occupations may help maintain a robust mental health, especially by reducing stress symptoms during middle age. These results broaden previous findings suggesting that CR relates to affective components of mental health in middle aged and older adults.

The Complex Relationship between Sleep and Cognitive Reserve: A Narrative Review Based on Human Studies

Sleep and brain/cognitive/neural reserve significantly impact well-being and cognition throughout life. This review aims to explore the intricate relationship between such factors, with reference to their effects on human cognitive functions. The specific goal is to understand the bidirectional influence that sleep and reserve exert on each other. Up to 6 February 2024, a methodical search of the literature was conducted using the PubMed database with terms related to brain, cognitive or neural reserve, and healthy or disturbed sleep. Based on the inclusion criteria, 11 articles were selected and analyzed for this review. The articles focus almost exclusively on cognitive reserve, with no explicit connection between sleep and brain or neural reserve. The results evidence sleep's role as a builder of cognitive reserve and cognitive reserve's role as a moderator in the effects of physiological and pathological sleep on cognitive functions. In conclusion, the findings of the present review support the notion that both sleep and cognitive reserve are critical factors in cognitive functioning. Deepening comprehension of the interactions between them is essential for devising strategies to enhance brain health and resilience against age- and pathology-related conditions.

A Neuropathology Case Report of a Woman with Down Syndrome who Remained Cognitively Stable

In this neuropathology case report, we present findings from an individual with Down syndrome (DS) who remained cognitively stable despite Alzheimer's disease (AD) neuropathology. Clinical assessments, fluid biomarkers, neuroimaging, and neuropathological examinations were conducted to characterize her condition. Notably, her ApoE genotype was E2/3, which is associated with a decreased risk of dementia. Neuroimaging revealed stable yet elevated amyloid profiles and moderately elevated tau levels, while neuropathology indicated intermediate AD neuropathologic change with Lewy body pathology and cerebrovascular pathology. Despite the presence of AD pathology, the participant demonstrated intact cognitive functioning, potentially attributed to factors such as genetic variations, cognitive resilience, and environmental enrichment. The findings suggest a dissociation between clinical symptoms and neuropathological changes, emphasizing the complexity of AD progression in DS. Further investigation into factors influencing cognitive resilience in individuals with DS, including comorbidities and social functioning, is warranted. Understanding the mechanisms underlying cognitive stability in DS could offer insights into resilience to AD neuropathology in people with DS and in the general population and inform future interventions.

Childhood engagement in cognitively stimulating activities moderates relationships between brain structure and cognitive function in adulthood

Greater engagement in cognitively stimulating activities (CSA) during adulthood has been shown to protect against neurocognitive decline, but no studies have investigated whether CSA during childhood protects against effects of brain changes on cognition later in life. The current study tested the moderating role of childhood CSA in the relationships between brain structure and cognitive performance during adulthood. At baseline (N=250) and 5-year follow-up (N=204) healthy adults aged 20-80 underwent MRI to assess four structural brain measures and completed neuropsychological tests to measure three cognitive domains. Participants were categorized into low and high childhood CSA based on self-report questionnaires. Results of multivariable linear regressions analyzing interactions between CSA, brain structure, and cognition showed that higher childhood CSA was associated with a weaker relationship between cortical thickness and memory at baseline, and attenuated the effects of change in cortical thickness and brain volume on decline in processing speed over time. These findings suggest higher CSA during childhood may mitigate the effects of brain structure changes on cognitive function later in life.

Handicraft art leisure activities and cognitive reserve

ObjectiveOlder individuals face a higher likelihood of developing dementia. The rate of cognitive decline resulting from dementia is not equivalent for all, as some patients with dementia are able to function independently longer than others, despite having similar disease burden. The cognitive reserve (CR) theory provides one explanation for the differing rate of decline. CR suggests that there are factors-most notably, educational attainment and occupational attainment-that can protect against the cognitive decline. Although the beneficial effects of these notable CR factors are clear, not all are easily modifiable. Participation in leisure activities may represent a more easily modifiable factor. Some research hints at beneficial effects of leisure activities, although specific leisure activities have not been well examined. The present study examined the relations between handicraft art leisure activities (HALAs) and multiple cognitive domains. MethodArchival WAIS-IV and demographic data for 50 California retirement community residents were examined. ResultsHALA participation accounted for statistically significant variance in working memory performance (R2 = .40, β = .24%) over and above the established CR factors of age, depression, educational attainment, and occupational attainment. In addition, HALA participation was related to a better ability to perform abstract visual information tasks (Block Design subtest, r = .28, p = .05) and non-verbal reasoning tasks (Visual Puzzles subtest, r = .38, p = .008). ConclusionsHALA participation among older adults could contribute to the retention of cognitive function, supporting the role of HALA participation as a CR factor.

Effects of cognitive reserve on cognitive frailty among older adults: A population-based prospective cohort study

AIM

We investigated the effect of lifespan cognitive reserve and its components on cognitive frailty among older adults.

METHODS

A total of 4922 participants aged ≥65 years were recruited in 2008 and were followed up in 2011 from the Chinese Longitudinal Healthy Longevity Survey. Cognitive frailty was determined through the simultaneous presence of physical frailty (pre-frailty or frailty) and mild cognitive impairment, excluding concurrent dementia. The assessment of physical frailty and mild cognitive impairment was based on the Fatigue, Resistence, Ambulation, Illness, Loss of weight (FRAIL) (Fatigue, Resistence, Ambulation, Illness, Loss) and Mini-Mental State Examination scale, respectively. The lifespan cognitive reserve consisted of education attainment, occupational complexity and later-life leisure activities. We used logistic regression models to estimate the risk of cognitive frailty associated with the lifespan cognitive reserve and its components.

RESULTS

A higher level of lifespan cognitive reserve, higher educational attainment or leisure activities engagement, but not occupational complexity, were associated with lower risk of incident cognitive frailty. Furthermore, cognitive, social and physical activities were associated with lower risk of incident cognitive frailty.

CONCLUSION

Cognitive reserve, particularly educational attainment and leisure activities, can protect from cognitive frailty. This implicates that individuals should accumulate cognitive reserve in their lifespan, and older adults should actively participate in leisure activities to prevent cognitive frailty. Geriatr Gerontol Int 2024; 24: 398-403.

Relationship between lifestyle proxies of cognitive reserve and cortical regions in older adults

Introduction

With the rapid increase in the population over 65 years old, research on healthy aging has become one of the priorities in the research community, looking for a cost-effective method to prevent or delay symptoms of mild cognitive disorder or dementia. Studies indicate that cognitive reserve theory could be beneficial in this regard. The aim of this study was to investigate the potential relationship between lifestyle socio-behavioral proxies of cognitive reserve and cortical regions in adults with no subjective cognitive decline.

Methods

Overall, 58 participants, aged 65-85 years, were included in the data analysis (M = 71.83, SD = 5.02, 20.7% male). Cognitive reserve proxies were measured using the Cognitive Reserve Index questionnaire, while cortical volumes were obtained with the Siemens 1.5 T Avanto MRI scanner and further mapped using the Desikan-Killiany-Tourville (DKT) Atlas. Estimated intracranial volume and age were used as covariates.

Results

The results indicated that higher occupational complexity was associated with larger cortical volume in the left middle temporal gyrus, the left and right inferior temporal gyrus, and the left inferior parietal lobule, while a combined proxy (the total CRI score) showed a positive relationship with the volume of left middle temporal gyrus and inferior parietal lobule, and pars orbitalis in the right hemisphere.

Discussion

These results might indicate that more complex occupational activities and overall more intellectually and socially active life-style could contribute to better brain health, especially in regions known to be more vulnerable to Alzheimer's disease.

The Role of Insulin-like Growth Factor I in Mechanisms of Resilience and Vulnerability to Sporadic Alzheimer's Disease

Despite decades of intense research, disease-modifying therapeutic approaches for Alzheimer's disease (AD) are still very much needed. Apart from the extensively analyzed tau and amyloid pathological cascades, two promising avenues of research that may eventually identify new druggable targets for AD are based on a better understanding of the mechanisms of resilience and vulnerability to this condition. We argue that insulin-like growth factor I (IGF-I) activity in the brain provides a common substrate for the mechanisms of resilience and vulnerability to AD. We postulate that preserved brain IGF-I activity contributes to resilience to AD pathology as this growth factor intervenes in all the major pathological cascades considered to be involved in AD, including metabolic impairment, altered proteostasis, and inflammation, to name the three that are considered to be the most important ones. Conversely, disturbed IGF-I activity is found in many AD risk factors, such as old age, type 2 diabetes, imbalanced diet, sedentary life, sociality, stroke, stress, and low education, whereas the Apolipoprotein (Apo) E4 genotype and traumatic brain injury may also be influenced by brain IGF-I activity. Accordingly, IGF-I activity should be taken into consideration when analyzing these processes, while its preservation will predictably help prevent the progress of AD pathology. Thus, we need to define IGF-I activity in all these conditions and develop a means to preserve it. However, defining brain IGF-I activity cannot be solely based on humoral or tissue levels of this neurotrophic factor, and new functionally based assessments need to be developed.

The indirect effect of cognitive reserve on the relationship between age and cognition in pathological ageing: A cross-sectional retrospective study in an unselected and consecutively enrolled sample

Cognitive reserve (CR) allows individuals to maintain cognitive functionality even in the presence of pathologies. The compensation hypothesis suggests that CR plays an indirect role between age and cognitive decline, contrasting the negative effect of ageing on cognition. We test this hypothesis in an unselected and consecutively enrolled sample of memory clinic attendees (n = 134) who completed the CR Index questionnaire and three neuropsychological tests assessing global cognition (MMSE, FAB, CDT). Participants were divided into two groups based on standard diagnostic criteria (DSM-5): those who were cognitively impaired (n = 92) and those who were preserved (n = 42). A principal component analysis was used to extract a composite measure of global cognitive functioning from the three neuropsychological tests, and mediation analysis was used to examine the relationship between CR, age and global cognitive functioning in the two groups. Results revealed that: (i) age had a significant direct negative effect on the global cognitive score in both groups; (ii) the three socio-behavioural proxies of CR together suppress the direct negative relationship between age and global cognitive score in cognitively impaired patients but not in cognitively preserved participants. This study confirms the association between CR, age and cognition and allows us to validate its role in a population with cognitive impairment and extend findings to a low-to-middle educated population. These results hold important implications for public health and wellness promotion, emphasising the beneficial role of maintaining healthy and active physical, cognitive and social lifestyles.

Genetic propensity for cerebral amyloidosis and risk of mild cognitive impairment and Alzheimer's disease within a cognitive reserve framework

INTRODUCTION

We constructed a polygenic risk score (PRS) for β-amyloid (PRSAβ42) to proxy AD pathology and investigated its association with incident Alzheimer's disease (AD)/amnestic mild cognitive impairment (aMCI) and the influence of cognitive reserve (CR), proxied by educational years, on the relationship between PRSAβ42 and AD/aMCI risk.

METHODS

A total of 618 cognitive-normal participants were followed-up for 2.92 years. The association of PRSAβ42 and CR with AD/aMCI incidence was examined with COX models. Then we examined the additive interaction between PRSAβ42 and CR and the CR effect across participants with different PRSAβ42 levels.

RESULTS

Higher PRSAβ42 and CR were associated with a 33.9% higher risk and 8.3% less risk for AD/aMCI, respectively. An additive interaction between PRSAβ42 and CR was observed. High CR was associated with 62.6% less risk of AD/aMCI incidence only in the high-PRSAβ42 group.

DISCUSSION

A super-additive effect of PRSAβ42 and CR on AD/aMCI risk was observed. CR influence was evident in participants with high PRSAβ42.

Cognitive phenotypes in late-onset epilepsy: results from the atherosclerosis risk in communities study

Introduction

Cognitive phenotyping is a widely used approach to characterize the heterogeneity of deficits in patients with a range of neurological disorders but has only recently been applied to patients with epilepsy. In this study, we identify cognitive phenotypes in older adults with late-onset epilepsy (LOE) and examine their demographic, clinical, and vascular profiles. Further, we examine whether specific phenotypes pose an increased risk for progressive cognitive decline.

Methods

Participants were part of the Atherosclerosis Risk in Communities Study (ARIC), a prospective longitudinal community-based cohort study of 15,792 individuals initially enrolled in 1987-1989. LOE was identified from linked Centers for Medicare and Medicaid Services claims data. Ninety-one participants with LOE completed comprehensive testing either prior to or after seizure onset as part of a larger cohort in the ARIC Neurocognitive Study in either 2011-2013 or 2016-2017 (follow-up mean = 4.9 years). Cognitive phenotypes in individuals with LOE were derived by calculating test-level impairments for each participant (i.e., ≤1 SD below cognitively normal participants on measures of language, memory, and executive function/processing speed); and then assigning participants to phenotypes if they were impaired on at least two tests within a domain. The total number of impaired domains was used to determine the cognitive phenotypes (i.e., Minimal/No Impairment, Single Domain, or Multidomain).

Results

At our baseline (Visit 5), 36.3% met criteria for Minimal/No Impairment, 35% for Single Domain Impairment (with executive functioning/ processing speed impaired in 53.6%), and 28.7% for Multidomain Impairment. The Minimal/No Impairment group had higher education and occupational complexity. There were no differences in clinical or vascular risk factors across phenotypes. Of those participants with longitudinal data (Visit 6; n = 24), 62.5% declined (i.e., progressed to a more impaired phenotype) and 37.5% remained stable. Those who remained stable were more highly educated compared to those that declined.

Discussion

Our results demonstrate the presence of identifiable cognitive phenotypes in older adults with LOE. These results also highlight the high prevalence of cognitive impairments across domains, with deficits in executive function/processing speed the most common isolated impairment. We also demonstrate that higher education was associated with a Minimal/No Impairment phenotype and lower risk for cognitive decline over time.

Effects of Brain Maintenance and Cognitive Reserve on Age-Related Decline in Three Cognitive Abilities

OBJECTIVES

Age-related cognitive changes can be influenced by both brain maintenance (BM), which refers to the relative absence over time of changes in neural resources or neuropathologic changes, and cognitive reserve (CR), which encompasses brain processes that allow for better-than-expected behavioral performance given the degree of life-course-related brain changes. This study evaluated the effects of age, BM, and CR on longitudinal changes over 2 visits, 5 years apart, in 3 cognitive abilities that capture most of age-related variability.

METHODS

Participants included 254 healthy adults aged 20-80 years at recruitment. Potential BM was estimated using whole-brain cortical thickness and white matter mean diffusivity at both visits. Education and intelligence quotient (IQ; estimated with American National Adult Reading Test) were tested as moderating factors for cognitive changes in the 3 cognitive abilities.

RESULTS

Consistent with BM-after accounting for age, sex, and baseline performance-individual differences in the preservation of mean diffusivity and cortical thickness were independently associated with relative preservation in the 3 abilities. Consistent with CR-after accounting for age, sex, baseline performance, and structural brain changes-higher IQ, but not education, was associated with reduced 5-year decline in reasoning (β = 0.387, p = .002), and education was associated with reduced decline in speed (β = 0.237, p = .039).

DISCUSSION

These results demonstrate that both CR and BM can moderate cognitive changes in healthy aging and that the 2 mechanisms can make differential contributions to preserved cognition.

Cognitive reserve moderates the association between cerebral blood flow and language performance in older adults with mild cognitive impairment

Higher cognitive reserve (CR) may offer protection from cognitive changes associated with reduced cerebral blood flow (CBF). We investigated CR as a moderator of the effect of CBF on cognition in older adults with mild cognitive impairment (MCI; N = 46) and those who are cognitively unimpaired (CU; N = 101). Participants underwent arterial spin labeling MRI, which was used to quantify CBF in 4 a priori regions. Estimated verbal intelligence quotient (VIQ) served as a proxy for CR. Multiple linear regressions examined whether VIQ moderated associations between CBF and cognition and whether this differed by cognitive status. Outcomes included memory and language performance. There were 3-way interactions (CBF*VIQ*cognitive status) on category fluency when examining hippocampal, superior frontal, and inferior frontal CBF. Follow-up analyses revealed that, within the MCI but not CU group, there were CBF*VIQ interactions on fluency in all a priori regions examined, where there were stronger, positive associations between CBF and fluency at higher VIQ. Conclusion: In MCI, higher CR plays a role in strengthening CBF-fluency associations.

Representativeness of samples enrolled in Alzheimer's disease research centers

To generalize findings on the mechanisms and prognosis in Alzheimer's disease and related dementias (ADRD), it is critical for ADRD research to be representative of the population. Sociodemographic and health characteristics across ethnoracial groups included in the National Alzheimer's Coordinating Center sample (NACC) were compared to the nationally representative Health and Retirement Study (HRS).

Baseline NACC data (n = 36,639) and the weighted 2010 HRS wave (N = 52,071,840) were included. We assessed covariate balance by calculating standardized mean differences across harmonized covariates (i.e., sociodemographic, health).

NACC participants were older, more educated, with worse subjective memory and hearing, but endorsed fewer depressive symptoms compared to HRS participants. While all racial and ethnic groups in NACC differed from HRS participants in the same way overall, these differences were further amplified between racial and ethnic groups.

NACC participants do not represent the U.S. population in key demographic and health factors, which differed by race and ethnicity.

HIGHLIGHTS

We examined selection factors included in NACC studies compared to a nationally representative sample.Selection factors included demographic and health factors and self-reported memory concerns.Results suggest that NACC participants are not representative of the U.S. population.Importantly, selection factors differed across racial and ethnic groups.Findings are suggestive of selection bias within NACC studies.

Electroconvulsive Therapy Impact on Memory Performance in Patients With Depression

INTRODUCTION

The safety of electroconvulsive therapy has improved greatly over the last decades, making the potentially adverse effects on memory and other neurocognitive functions the main clinical aspect of concern in the present. In Colombia, the general population and healthcare professionals (even some psychiatrists) seem to have mostly negative opinions towards electroconvulsive therapy treatment, but maybe this could be reconsidered if more information is provided; therefore, the aim of the present study was to evaluate the changes in memory and the severity of the symptoms in a group of patients with severe depression before and after electroconvulsive therapy.

METHODS

Twenty-three patients ranging in age from 23 to 70 years from the electroconvulsive therapy service at the San Juan de Dios Clinic (Manizales, Colombia) were recruited in order to assess the effect of electroconvulsive therapy on memory in patients with severe depression. Depressive symptoms and memory were assessed with the Hamilton Depression Scale (HAMD) and Rey Auditory Verbal Learning Test (RAVLT), respectively. The assessment was administered to participants before the initial treatment of electroconvulsive therapy series (0-1 day) and 2 days after their last treatment.

RESULTS

Electroconvulsive therapy resulted in significant improvement in the rating of depression. There were no significant differences in the five learning trials, delayed recall, learning and forgetting scores from pre-treatment to post-treatment. Significant pre-treatment/post-treatment differences were found in the delayed recognition trial.

CONCLUSIONS

Pre- and post- electroconvulsive therapy cognitive assessment is a feasible and useful procedure. In general, memory performance does not worsen after electroconvulsive therapy in patients with depression. Only delayed recognition is affected a few days following electroconvulsive therapy, particularly in patients with low educational level and bitemporal (BT) electrode placement.

Diversity in verbal fluency performance and its associations with MRI-informed brain age matrices in normal ageing and neurocognitive disorders

INTRODUCTION

Category verbal fluency test (CVFT) has been widely used to assess and monitor the cognitive capacities in epidemiological studies and clinical trials. Pronounced discrepancy in CVFT performance has been found in individuals with different cognitive statuses. This study aimed to combine the psychometric and morphometric approaches to decode the complex verbal fluency performance in senior adults with normal ageing and neurocognitive disorders.

METHODS

This study adopted a two-stage cross-sectional design involving quantitative analyses of neuropsychological and neuroimaging data. In study I, capacity- and speed-based measures of CVFT were developed to evaluate the verbal fluency performance in normal ageing seniors (n = 261), those with mild cognitive impairment (n = 204), and those with dementia (n = 23) whose age range is from 65 to 85 years. In study II, structural magnetic resonance imaging-informed gray matter volume (GMV) and brain age matrices were calculated in a subsample (n = 52) from Study I through surface-based morphometry analysis. With age and gender as covariates, Pearson's correlation analysis was used to examine the associations of CVFT measures, GMV, and brain age matrices.

RESULTS

Speed-based measures showed extensive and stronger associations with other cognitive functions than capacity-based measures. The component-specific CVFT measures showed shared and unique neural underpinnings with lateralized morphometric features. Moreover, the increased CVFT capacity was significantly correlated with younger brain age in mild neurocognitive disorder (NCD) patients.

CONCLUSION

We found that the diversity of verbal fluency performance in normal ageing and NCD patients could be explained by a combination of memory, language, and executive abilities. The component-specific measures and related lateralized morphometric correlates also highlight the underlying theoretical meaning of verbal fluency performance and its clinical utility in detecting and tracing the cognitive trajectory in individuals with accelerated ageing.

Pre-Treatment Breast Cancer Patients Show Neural Differences in Frontal Alpha Asymmetry

Cognitive impairment has been observed consistently in a subset of breast cancer survivors. Yet, still unknown is whether neural and behavioral effects of cancer exist prior to treatment, which may contribute to later cognitive decline. The current study investigated pre-treatment differences in attention performance and frontal alpha asymmetry (FAA), an established neural index of inhibitory control, in non-metastatic breast cancer patients (n = 42) compared with healthy controls (n = 28). We additionally investigated whether differences between groups appear in specific cuing conditions and across different stages of information processing. Participants underwent EEG while completing the Attention Network Task (ANT), a cognitive measure of alerting, orienting, and inhibitory control of attention. Results revealed no behavioral differences between patients and controls but significantly greater right-hemisphere alpha activity (reduced inhibitory control) in patients, particularly to uninformative (no cue, double cue) versus informative (valid cue) cues and in later stages of information processing (400-800 ms post-stimulus). Results suggest neural differences between groups to uncertain stimulus environments that have yet to manifest behaviorally. FAA may thus serve as a unique neural correlate that could potentially be used to predict later cognitive decline.

Sex-Specific Protective Effects of Cognitive Reserve on Age-Related Cognitive Decline: A 5-Year Prospective Cohort Study

BACKGROUND AND OBJECTIVES

Females have a higher age-adjusted incidence of Alzheimer disease than males but the reasons for this remain unclear. One proposed contributing factor is that, historically, females had less access to education and, therefore, may accumulate less cognitive reserve. However, educational attainment is confounded by IQ, which in itself is a component of cognitive reserve and does not differ between sexes. Steeper age-related cognitive declines are associated with increased risk of dementia. We, therefore, evaluated the moderating effects of 2 proxies for cognitive reserve, education and IQ, on the steepness of age-related declining cognitive trajectories in unimpaired older males and females.

METHODS

The Tasmanian Healthy Brain Project, a long-term cohort study, recruited healthy Australians aged 50-80 years without cognitive impairment. Baseline cognitive reserve was measured using educational history and IQ, measured by the Wechsler Test of Adult Reading, Full Scale Predicted IQ (WTAR-FSIQ). Cognitive trajectories for language, executive function, and episodic and working memory over 5 years were extracted from neuropsychological assessments. The adjusted effects of education, estimated IQ, and APOE allelic variant on cognitive trajectories were compared between males and females.

RESULTS

Five hundred sixty-two individuals (mean [SD] age 60 [6.7] years; 68% male; 33% APOE ε4+) were followed up over 5 years with 1,924 assessments and 24,946 cognitive test scores (annualized attrition rate 6.6% per year). Estimated IQ correlated with years of education (p < 0.001). Estimated IQ interacted with sex to moderate age-related cognitive trajectories (p = 0.03; adjusted for education); lower IQ males experienced steeper declining trajectories than higher IQ males, but lower IQ females had similar steepness of declining trajectories to higher IQ females. Education was not associated with rate of cognitive decline (p = 0.67; adjusted for WTAR-FSIQ). There were no significant differences in age-related cognitive trajectories between APOE genotypes in either sex.

DISCUSSION

IQ, a measure of cognitive reserve, predicted the steepness of declining cognitive trajectories in males only. Education did not explain as much variation in cognitive trajectories as IQ. Our findings do not support the hypothesis that historical sex disparities in access to education contribute to the higher female incidence of Alzheimer disease.

Understanding racial differences in computerized neurocognitive test performance and symptom-reporting to deliver culturally competent patient-centered care for sport-related concussion

OBJECTIVE

This study examined neurocognitive performance and symptoms between concussed Black and White collegiate athletes at baseline, post-injury, and change from baseline to post-injury.

METHOD

The Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) was used to measure neurocognitive performance and four concussion symptom clusters for 235 concussed collegiate athletes. Between-groups differences were documented at baseline and post-injury, along with change in scores for sex/race, and sport/race groups, using ANOVAs. Baseline scores, and days-to-post-test were covariates in post-injury comparisons. Symptom endorsement by race was evaluated using chi-square analyses.

RESULTS

At baseline, group comparisons by race and sex showed that Black male/female athletes scored lower on reaction time (RT; p = .008), White females scored higher on verbal memory (VerbMem; p = .001), Black females scored lower on visual motor processing speed (VMS; p = .001), and Black football athletes scored slower/poorer on RT (p = .001) and VMS (p = .006). Post-injury, Black males scored lower on visual memory (VisMem; p = .005) and VMS (p = .002), and Black football athletes scored slower on VMS (p = .005), whereas White non-football athletes scored higher on VerbMem (p = .002) and reported fewer symptoms. Significant time-by-sport/race interactions were found for VerbMem (p < .001), VisMem (p < .001) and reported symptoms. With respect to post-injury symptom scores/endorsement, Black athletes scored significantly higher for physical (p = .01) and sleep (p = .01) symptoms.

CONCLUSION

These findings drive the conversation of how subjective measures of symptoms, and objective clinical concussion measures, may relate to the concussion recovery process and providing a culturally competent clinical management approach for diverse patients.

Prodromal Motoric Cognitive Risk Syndrome and Everyday Function

BACKGROUND

Motoric cognitive risk syndrome (MCR), a pre-dementia syndrome characterized by subjective cognitive complaints and slow gait, is associated with disability in instrumental activities of daily living. It is unknown whether these functional limitations occur even before this pre-dementia syndrome is diagnosed.

OBJECTIVE

To assess profiles of complex and instrumental activities of daily living in the prodromal stages of MCR.

METHODS

We examined functional profiles in 46 older adults (mean age 79 years, 59% women) living in the community with normal cognition at baseline who developed MCR over follow-up ('pre-MCR') with 264 older adults (mean age 75 years, 57% women) who remained cognitively intact over the follow-up period.

RESULTS

Pre-MCR individuals had more limitations on complex everyday function at baseline compared to normal controls in multivariable logistic regression models (odds ratio 1.21). Pre-MCR cases at baseline had limitations in handling finances (odds ratio 3.0) and performing hobbies (odds ratio 5.5) as compared to normal controls. Pre-MCR cases had a greater difference in the number of complex functional limitations from baseline to MCR compared to the difference from baseline to final visit for the controls (1.2±3.0 versus 0.5±2.2, p < 0.001).

CONCLUSIONS

Limitations in complex everyday tasks arise in the prodromal stages of MCR and can assist in risk prognostication.

Occupational complexity and cognition in the FINGER multidomain intervention trial

INTRODUCTION

Lifetime exposure to occupational complexity is linked to late-life cognition, and may affect benefits of preventive interventions.

METHODS

In the 2-year multidomain Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER), we investigated, through post hoc analyses (N = 1026), the association of occupational complexity with cognition. Occupational complexity with data, people, and substantive complexity were classified through the Dictionary of Occupational Titles.

RESULTS

Higher levels of occupational complexity were associated with better baseline cognition. Measures of occupational complexity had no association with intervention effects on cognition, except for occupational complexity with data, which was associated with the degree of intervention-related gains for executive function.

DISCUSSION

In older adults at increased risk for dementia, higher occupational complexity is associated with better cognition. The cognitive benefit of the FINGER intervention did not vary significantly among participants with different levels of occupational complexity. These exploratory findings require further testing in larger studies.

Cognitive reserve: a multidimensional protective factor in Parkinson's disease related cognitive impairment

We explored the association between cognitive reserve (CR) and Parkinson' s disease (PD) related cognitive deterioration.Forty PD patients and 12 matched healthy controls (HC) were enrolled. The PD group was balanced for the presence/absence of cognitive impairment. All participants underwent MOCA. CR was measured by the Brief Intelligence Test, and a new comprehensive tool, named Cognitive Reserve Test (CoRe-T), including sections on leisure activities and creativity.Participants with higher CR obtained a better MOCA score irrespective of the group they belonged to. At the same time, irrespective of the CR level, the performance of the HC group was always better in comparison to the PD group. Within the PD group, a higher frequency of leisure activities was associated to be cognitively unimpaired, independently by the severity of motor symptoms and age.CR could help to cope with PD-related cognitive decline. Its multidimensional nature could have important applications in prevention and rehabilitation interventions.

Cognitive Reserve and Related Constructs: A Unified Framework Across Cognitive and Brain Dimensions of Aging

Cognitive reserve and related constructs are valuable for aging-related research, but consistency and clarification of terms is needed as there is still no universally agreed upon nomenclature. We propose a new set of definitions for the concepts of reserve, maintenance, and resilience, and we invoke parallel concepts for each that are applicable to cognition and to brain. Our definitions of reserve and resilience correspond reasonably well to dictionary definitions of these terms. We demonstrate logical/methodological problems that arise from incongruence between commonly used conceptual and operational definitions. In our view, cognitive reserve should be defined conceptually as one's total cognitive resources at a given point in time. IQ and education are examples of common operational definitions (often referred to as proxies) of cognitive reserve. Many researchers define cognitive reserve conceptually as a property that allows for performing better than expected cognitively in the face of aging or pathology. Performing better than expected is demonstrated statistically by interactions in which the moderator is typically IQ or education. The result is an irreconcilable situation in which cognitive reserve is both the moderator and the moderation effect itself. Our proposed nomenclature resolves this logical inconsistency by defining performing better than expected as cognitive resilience. Thus, in our usage, we would test the hypothesis that high cognitive reserve confers greater cognitive resilience. Operational definitions (so-called proxies) should not conflate factors that may influence reserve-such as occupational complexity or engagement in cognitive activities-with cognitive reserve itself. Because resources may be depleted with aging or pathology, one's level of cognitive reserve may change over time and will be dependent on when assessment takes place. Therefore, in addition to cognitive reserve and cognitive resilience, we introduce maintenance of cognitive reserve as a parallel to brain maintenance. If, however, education is the measure of reserve in older adults, it precludes assessing change or maintenance of reserve. Finally, we discuss consideration of resistance as a subcategory of resilience, reverse causation, use of residual scores to assess performing better than expected given some adverse factor, and what constitutes high vs. low cognitive reserve across different studies.

The roles of executive functioning, simple attention, and medial temporal lobes in early learning, late learning, and delayed recall

Fractionating performance of a verbal list-learning test can provide a nuanced interpretation of the relationship between brain networks and learning and memory abilities. Within older adult samples, including those with mild cognitive impairment and Alzheimer’s disease, cortical volumes for attention and executive functioning networks correlate more strongly with neuropsychological performance measures of early learning trials relative to late learning and delayed recall. In contrast, medial temporal lobe (MTL) structures, such as the hippocampus, are more strongly correlated to performance on late learning and delayed recall measures relative to early learning. We sought to extend these findings by evaluating the contributions of simple attention, executive function (EF), and MTL structures to learning and recall in a cognitively heterogeneous sample of older adults that included healthy controls (n = 54), adults with MCI (n = 63), and those with dementia (n = 13). We used canonical correlation analyses to test the hypotheses that the contributions of EF, simple attention, and the MTL to verbal memory would differ across phases of learning and recall. Results showed that relationships between the MTL and memory were the only ones to demonstrate a graded pattern of association, ranging from r = .46 to .57 across early learning, late learning, and delayed recall. Simple attention and EF were both significantly and moderately related to learning and recall, but those relationships did not vary across phases as hypothesized. We explore alternative interpretations for our discrepant findings, including the influence of sample characteristics and methodology, advocating for multivariate approaches.

Joint Models for Estimating Determinants of Cognitive Decline in the Presence of Survival Bias

BACKGROUND

Identifying determinants of cognitive decline is crucial for developing strategies to prevent Alzheimer's disease and related dementias. However, determinants of cognitive decline remain elusive, with inconsistent results across studies. One reason could be differential survival. Cognitive decline and many exposures of interest are associated with mortality making survival a collider. Not accounting for informative attrition can result in survival bias. Generalized estimating equations (GEE) and linear mixed-effects model (LME) are commonly used to estimate effects of exposures on cognitive decline, but both assume mortality is not informative. Joint models combine LME with Cox proportional hazards models to simultaneously estimate cognitive decline and the hazard of mortality.

METHODS

Using simulations, we compared estimates of the effect of a binary exposure on rate of cognitive decline from GEE, weighted GEE using inverse-probability-of-attrition weights, and LME to joint models under several causal structures of survival bias.

RESULTS

We found that joint models with correctly specified relationship between survival and cognition performed best, producing unbiased estimates and appropriate coverage. Even those with misspecified relationship between survival and cognition showed advantage under causal structures consistent with survival bias. We also compared these models in estimating the effect of education on cognitive decline after dementia diagnosis using Framingham Heart Study data. Estimates of the effect of education on cognitive decline from joint models were slightly attenuated with similar precision compared with LME.

CONCLUSIONS

In our study, joint models were more robust than LME, GEE, and weighted GEE models when evaluating determinants of cognitive decline.

The Impact of Early Neighborhood Cohesion, and Its Mechanism, on Cognitive Function in Later Life

Objectives

This study aimed to explore the impact of early neighborhood cohesion, and its mechanism, on cognitive function in later life.

Methods

In total, 10,727 Chinese elderly, aged 60-90, forming two datasets (2014 and 2018) from the China Health and Retirement Longitudinal Study (CHARLS) were used as a sample. Childhood neighborhood cohesion was measured by the extent of how much neighbors were willing to help and how close-knit neighbors were. Mini-Mental State Examination (MMSE) and Center for Epidemiologic Studies Depression Scale (CESD-10) were used to assess the cognitive functions and depression of the elderly. We used a structural equation model to examine the relationship between early neighborhood cohesion and late-life cognitive function and conducted bootstrapping analyses to assess the mechanism.

Results

Cognitive function was positively predicted by childhood neighborhood cohesion (β = 0.06, p < 0.001), and cognitive function of the elderly were also positively predicted through the mediating effects of childhood friendships, which included depression and social activity participation as two chain paths.

Conclusion

The findings suggest that childhood neighborhood cohesion positively predicts cognitive function among elderly people through the mediating roles of childhood friendship, depression, and social activity engagement. Childhood neighborhood cohesion is correlated with better childhood friendships, then to fewer depression symptoms and greater elderly social activity participation, and finally to better cognitive functions in the elderly.

Relationship of sex differences in cortical thickness and memory among cognitively healthy subjects and individuals with mild cognitive impairment and Alzheimer disease

BACKGROUND

An aging society has increased rates of late onset Alzheimer disease dementia (ADD), the most common form of age-related dementia. This neurodegenerative disease disproportionately affects women.

METHODS

We use data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to examine sex differences in cortical thickness (CT) and memory performance. Analyses of covariance (ANCOVA) models were used to examine effects of sex and diagnosis (DX) on CT and verbal memory. For regions demonstrating significant interaction effects of sex and DX, we tested whether sex moderated cognition-thickness relationships. We used machine learning as a complementary method to explore multivariate CT differences between women and men.

RESULTS

Women demonstrated greater CT in many brain regions. More specifically, men showed relatively consistent CT declines in all stages, from normal control (NC) to ADD in the bilateral cingulate cortex, bilateral temporal regions, and left precuneus; women had more stable CT in these regions between NC and mild cognitive impairment (MCI) stages, but sharper declines from MCI to ADD. Similarly, for the Rey Auditory Verbal Learning Test (RAVLT), ANCOVA analyses showed that women had significantly better immediate and delayed recall scores than men, at NC and MCI stages, but greater differences, cross-sectionally, from MCI to ADD than men. We found significant sex moderation effects between RAVLT-immediate scores and CT of right isthmus-cingulate for all subjects across DX. Partial correlation analyses revealed that increased CT of right isthmus-cingulate was associated with better verbal learning in women, driven by positron emission tomography defined amyloid positive (Aβ+) subjects. Significant sex-moderation effects in cognition-thickness relationships were further found in the right middle-temporal, left precuneus, and left superior temporal regions in Aβ+ subjects. Using a machine learning approach, we investigated multivariate CT differences between women and men, showing an accuracy in classification of 75% for Aβ+ cognitively NC participants.

CONCLUSIONS

Sex differences in memory and CT can play a key role in the different vulnerability and progression of ADD in women compared to men. Machine learning indicates sex differences in CT are most relevant early in the ADD neurodegeneration.

Triglyceride Glucose Index is Related with the Risk of Mild Cognitive Impairment in Type 2 Diabetes

BACKGROUND

The triglyceride glucose (TyG) index reflects insulin resistance; the latter being associated with mild cognitive impairment (MCI).

OBJECTIVE

To investigate the clinical value of the TyG index to identify MCI in patients living with type 2 diabetes (T2D) using a cross-sectional study.

METHODS

This cross-sectional study was performed on 517 patients with T2D. The diagnosis of MCI was based on criteria established by the National Institute on Aging-Alzheimer's Association workgroup, and patients were divided into the MCI group and the normal cognitive function (NCF) group. The logistic regression analysis determines whether the TyG index is related to MCI. Subsequently, we constructed the receiver operating characteristic curve (ROC) and calculated the area under the curve (AUC). The nomogram model of the influence factor was established and verified.

RESULTS

Compared to the type 2 diabetes-normal cognitive function (T2D-NCF) group, the MCI subjects were olderand had higher TyG indexes, lower cognitive scores, and lower education levels (p < 0.01). After adjusting for the confounders, the TyG index was associated with MCI (OR = 7.37, 95% CI = 4.72-11.50, p < 0.01), and TyG-BMI was also associated with MCI (OR = 1.02, 95% CI = 1.01-1.02, p<0.01). The TyG index AUC was 0.79 (95% CI = 0.76-0.83). The consistency index of the nomogram was 0. 83[95% CI (0. 79, 0. 86)].

CONCLUSION

Our results indicate that the TyG index and TyG-BMI are associated with MCI in T2D patients, and the TyG index is an excellent indicator of the risk of MCI in T2D patients. The nomogram incorporating the TyG index is useful to predict MCI risk in patients with T2D.

Cognitive Reserve and Related Constructs: A Unified Framework Across Cognitive and Brain Dimensions of Aging

Cognitive reserve and related constructs are valuable for aging-related research, but consistency and clarification of terms is needed as there is still no universally agreed upon nomenclature. We propose a new set of definitions for the concepts of reserve, maintenance, and resilience, and we invoke parallel concepts for each that are applicable to cognition and to brain. Our definitions of reserve and resilience correspond reasonably well to dictionary definitions of these terms. We demonstrate logical/methodological problems that arise from incongruence between commonly used conceptual and operational definitions. In our view, cognitive reserve should be defined conceptually as one's total cognitive resources at a given point in time. IQ and education are examples of common operational definitions (often referred to as proxies) of cognitive reserve. Many researchers define cognitive reserve conceptually as a property that allows for performing better than expected cognitively in the face of aging or pathology. Performing better than expected is demonstrated statistically by interactions in which the moderator is typically IQ or education. The result is an irreconcilable situation in which cognitive reserve is both the moderator and the moderation effect itself. Our proposed nomenclature resolves this logical inconsistency by defining performing better than expected as cognitive resilience. Thus, in our usage, we would test the hypothesis that high cognitive reserve confers greater cognitive resilience. Operational definitions (so-called proxies) should not conflate factors that may influence reserve-such as occupational complexity or engagement in cognitive activities-with cognitive reserve itself. Because resources may be depleted with aging or pathology, one's level of cognitive reserve may change over time and will be dependent on when assessment takes place. Therefore, in addition to cognitive reserve and cognitive resilience, we introduce maintenance of cognitive reserve as a parallel to brain maintenance. If, however, education is the measure of reserve in older adults, it precludes assessing change or maintenance of reserve. Finally, we discuss consideration of resistance as a subcategory of resilience, reverse causation, use of residual scores to assess performing better than expected given some adverse factor, and what constitutes high vs. low cognitive reserve across different studies.

Paradoxical cognitive trajectories in men from earlier to later adulthood

Because longitudinal studies of aging typically lack cognitive data from earlier ages, it is unclear how general cognitive ability (GCA) changes throughout the life course. In 1173 Vietnam Era Twin Study of Aging (VETSA) participants, we assessed young adult GCA at average age 20 and current GCA at 3 VETSA assessments beginning at average age 56. The same GCA index was used throughout. Higher young adult GCA and better GCA maintenance were associated with stronger specific cognitive abilities from age 51 to 73. Given equivalent GCA at age 56, individuals who had higher age 20 GCA outperformed those whose GCA remained stable in terms of memory, executive function, and working memory abilities from age 51 to 73. Thus, paradoxically, despite poorer maintenance of GCA, high young adult GCA still conferred benefits. Advanced predicted brain age and the combination of elevated vascular burden and APOE-ε4 status were associated with poorer maintenance of GCA. These findings highlight the importance of distinguishing between peak and current GCA for greater understanding of cognitive aging.

Cognitive Resilience in Brain Health and Dementia Research

With the expected rise in Alzheimer's disease and related dementias (ADRD) in the coming decades due to the aging population and a lack of effective disease-modifying treatments, there is a need for preventive strategies that may tap into resilience parameters. A wide array of resilience strategies has been proposed including genetics, socioeconomic status, lifestyle modifications, behavioral changes, and management of comorbid disease. These different strategies can be broadly classified as distinguishing between modifiable and non-modifiable risk factors, some of which can be quantified so that their clinical intervention can be effectively accomplished. A clear shift in research focus from dementia risk to addressing disease resistance and resilience is emerging that has provided new potential therapeutic targets. Here we review and summarize the latest investigations of resilience mechanisms and methods of quantifying resilience for clinical research. These approaches include identifying genetic variants that may help identify novel pathways (e.g., lipid metabolism, cellular trafficking, synaptic function, inflammation) for therapeutic treatments and biomarkers for use in a precision medicine-like regimen. In addition, innovative structural and molecular neuroimaging analyses may assist in detecting and quantifying pathological changes well before the onset of clinical symptoms setting up the possibility of primary and secondary prevention trials. Lastly, we summarize recent studies demonstrating the study of resilience in caregivers of persons living with dementia may have direct and indirect impact on the quality of care and patient outcomes.

Alcohol consumption and MRI markers of brain structure and function: Cohort study of 25,378 UK Biobank participants

Moderate alcohol consumption is widespread but its impact on brain structure and function is contentious. The relationship between alcohol intake and structural and functional neuroimaging indices, the threshold intake for associations, and whether population subgroups are at higher risk of alcohol-related brain harm remain unclear. 25,378 UK Biobank participants (mean age 54.9 ± 7.4 years, 12,254 female) underwent multi-modal MRI 9.6 ± 1.1 years after study baseline. Alcohol use was self-reported at baseline (2006-10). T1-weighted, diffusion weighted and resting state images were examined. Lower total grey matter volumes were observed in those drinking as little as 7-14 units (56-112 g) weekly. Higher alcohol consumption was associated with multiple markers of white matter microstructure, including lower fractional anisotropy, higher mean and radial diffusivity in a spatially distributed pattern across the brain. Associations between functional connectivity and alcohol intake were observed in the default mode, central executive, attention, salience and visual resting state networks. Relationships between total grey matter and alcohol were stronger than other modifiable factors, including blood pressure and smoking, and robust to unobserved confounding. Frequent binging, higher blood pressure and BMI steepened the negative association between alcohol and total grey matter volume. In this large observational cohort study, alcohol consumption was associated with multiple structural and functional MRI markers in mid- to late-life.

Novelty-like activation of locus coeruleus protects against deleterious human pretangle tau effects while stress-inducing activation worsens its effects

The earliest abnormality associated with Alzheimer's disease (AD) is the presence of persistently phosphorylated pretangle tau in locus coeruleus (LC) neurons. LC neuron numbers and fiber density are positive predictors of cognition prior to death. Using an animal model of LC pretangle tau, we ask if LC activity patterns influence the sequelae of pretangle tau. We seeded LC neurons with a pretangle human tau gene. We provided daily novelty- or stress-associated optogenetic activation patterns to LC neurons for 6 weeks in mid-adulthood and, subsequently, probed cognitive and anatomical changes. Prior LC phasic stimulation prevented spatial and olfactory discrimination deficits and preserved LC axonal density. A stress-associated activation pattern increased indices of anxiety and depression, did not improve cognition, and worsened LC neuronal health. These results argue that variations in environmental experiences associated with differing LC activity patterns may account for individual susceptibility to development of AD in humans.

Healthy memory aging - the benefits of regular daily activities increase with age

As the number of older adults increases, so does the pressure on health care systems due to age-related disorders. Attempts to reduce cognitive decline have focused on individual interventions such as exercise or diet, with limited success. This study adopted a different approach by investigating the impact of combined daily activities on memory decline. We used data from the National Institute of Aging’s Health and Retirement Study to explore two new questions: does combining activities affect memory decline, and if yes, does this impact change across the lifespan? We created a new machine learning model using 33 daily activities and involving 3210 participants. Our results showed that the effect of combined activities on memory decline was stronger than any individual activity’s impact. Moreover, this effect increased with age, whereas the importance of historical factors such as education, and baseline memory decreased. The present findings point out the importance of selecting multiple, diverse activities for older adults as they age. These results could have a significant impact on aging health policies promoting new programs such as social prescribing.

Twenty-Four-Hour Blood Pressure Variability Is Associated With Lower Cognitive Performance in Young Women With a Recent History of Preeclampsia

BACKGROUND

Women with a history of preeclampsia (hxPE) exhibit sustained arterial stiffness and elevated blood pressure postpartum. Aortic stiffness and 24-hour blood pressure variability (BPV) are associated with age-related cognitive decline. Although hxPE is related to altered cognitive function, the association between aortic stiffness and BPV with cognitive performance in young women with hxPE has not been investigated. The objectives of this study were to (i) test whether cognitive performance is lower in young women with hxPE and (ii) determine whether aortic stiffness and BPV are associated with cognitive performance independent of 24-hour average blood pressure.

METHODS

Women with hxPE (N = 23) and healthy pregnancy controls (N = 38) were enrolled 1-3 years postpartum. Cognitive performance was assessed in domains of memory, processing speed, and executive function. Twenty-four-hour ambulatory blood pressure monitoring and carotid-femoral pulse wave velocity (cfPWV) were used to measure BPV and aortic stiffness, respectively.

RESULTS

Women with hxPE had slower processing speed (-0.56 ± 0.17 vs. 0.34 ± 0.11 Z-score, P < 0.001) and lower executive function (-0.43 ± 0.14 vs. 0.31 ± 0.10 Z-score, P = 0.004) compared with controls independent of education, whereas memory did not differ. BPV and cfPWV (adjusted for blood pressure) did not differ between women with hxPE and controls. Greater diastolic BPV was associated with lower executive function independent of 24-hour average blood pressure and education in women with hxPE (r = -0.48, P = 0.03) but not controls (r = 0.15, P = 0.38).

CONCLUSIONS

Select cognitive functions are reduced postpartum in young women with a recent hxPE and linked with elevated 24-hour diastolic BPV.

The protective impact of education on brain structure and function in Alzheimer's disease

BACKGROUND

The Cognitive Reserve (CR) theory posits that brains with higher reserve can cope with more cerebral damage to minimize clinical manifestations. The aim of this study was to examine the effect of education (CR proxy) on brain structure and function in Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) patients and in cognitively healthy elderly (HC) individuals.

METHODS

Fifty-seven AD patients, 57 aMCI patients and 48 HCs were included to investigate the relationships between education years and gray matter volume (GMV), regional homogeneity (ReHo) and functional connectivity (FC) in brain regions to show associations with both structure and function. Taking the severity of the disease into account, we further assessed the relationships in AD stratified analyses.

RESULTS

In AD group, the GMV of the dorsal anterior cingulate cortex (dACC) and ReHo in the left inferior temporal cortex (ITC) were inversely associated with education years, after adjustment for age, sex, Mini-Mental State Examination (MMSE), and total intracranial volume or head motion parameters. Seed-based FC analyses revealed that education years were negatively correlated with the FC between the left anterior ITC and left mid frontal cortex as well as right superior frontal cortex and right angular gyrus. Stratified analyses results indicated that this negative relation between education and GMV, ReHo, FC was mainly present in mild AD, which was attenuated in moderate AD and aMCI groups.

CONCLUSIONS

Our results support the CR theory, and suggest that CR may be protective against AD related brain pathology at the early stage of clinical dementia. These findings could provide the locus of CR-related functional brain mechanisms and a specific time-window for therapeutic interventions to help AD patients to cope better with the brain pathological damage by increasing CR.

Cerebrospinal Fluid Biomarker Levels as Markers for Nursing Home Placement and Survival Time in Alzheimer's Disease

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers are associated with conversion from mild cognitive impairment to Alzheimer's disease (AD), but their predictive value for later end-points has been less evaluated with inconsistent results.

OBJECTIVE

We investigated potential relationships between CSF amyloid-β1-42 (Aβ42), phosphorylat- ed tau (P-tau), and total tau (T-tau) with time to nursing home placement (NHP) and life expectan- cy after diagnosis.

METHODS

This prospective observational study included 129 outpatients clinically diagnosed with mild-to-moderate AD who underwent a lumbar puncture. The CSF biomarkers were analysed with xMAP technology. Dates of institutionalisation and death were recorded.

RESULTS

After 20 years of follow-up, 123 patients (95%) were deceased. The participants with ab- normal P-tau and T-tau (A+ T+ (N)+) died earlier than those with normal P-tau/abnormal T-tau (A+ T- (N)+) (mean, 80.5 vs. 85.4 years). Linear associations were demonstrated between lower Aβ42 and shorter time to NHP (p = 0.017), and higher P-tau and younger age at death (p = 0.016). No correlations were detected between survival after AD diagnosis and CSF biomarkers. In sex- and-age-adjusted Cox regression models, higher P-tau and T-tau were independent predictors of shorter lifespan after diagnosis. In multivariate Cox models, older age and lower baseline cognitive status, but not elevated tau, significantly precipitated both institutionalisation and death.

CONCLUSION

These findings suggest that CSF biomarker levels plateau in the dementia phase of AD, which may limit their possible relationships with clinical end-points, such as NHP and survi- val time. However, the biomarkers reflect the central pathophysiologies of AD. In particular, patho- logic tau is associated with more advanced disease, younger age at onset, and earlier death.

How Can Cognitive Reserve Promote Cognitive and Neurobehavioral Health?

OBJECTIVE

This review is aimed at understanding how cognitive reserve and related concepts contribute to promoting neurobehavioral and cognitive health, consistent with goal of the 2020 national academy of neuropsychology (NAN) Annual Meeting.Research indicates that lifestyle factors such as achieving educational and work milestones, participating in leisure and social activities and IQ are all associated with reduced risk of cognitive decline in normal aging and of developing dementia. Many of these lifestyle factors have also been associated with better cognition in other psychiatric and neurological conditions. The cognitive reserve hypothesis posits that these lifestyle factors result in individual differences in the flexibility and adaptability of brain networks that may allow some people to cope better than others with age- or dementia-related brain changes. Recent evidence also supports the idea that specific genetic and lifestyle factors may help preserve a healthy brain or enhance brain reserve, a process that has been called brain maintenance. The complementary concept of brain reserve posits that structural brain features can guard against dementia and related conditions. This review defines these theoretical concepts, their research basis, how they are studied and their clinical applications.

CONCLUSION

Evidence supports the concept of reserve, which can be influenced by experiences in every stage of life. Focused research in this area can maximize the chance for successful intervention.

Genome-wide association study of occupational attainment as a proxy for cognitive reserve

Occupational attainment, which represents middle-age cognitive activities, is a known proxy marker of cognitive reserve for Alzheimer's disease. Previous genome-wide association studies (GWAS) have identified numerous genetic variants and revealed the genetic architecture of educational attainment, another marker of cognitive reserve. However, the genetic architecture and heritability for occupational attainment remain elusive. We performed a large-scale GWAS of occupational attainment with 248,847 European individuals from the UK Biobank using the proportional odds logistic mixed model method. In this analysis, we defined occupational attainment using the classified job levels formulated in the UK Standard Occupational Classification system considering the individual professional skill and academic level. We identified 30 significant loci (P < 5 × 10-8); 12 were novel variants, unassociated with other traits. Among them, four lead variants were associated with genes expressed in brain tissues by expression quantitative trait loci mapping from 10 brain regions: rs13002946, rs3741368, rs11654986, and rs1627527. The single nucleotide polymorphism (SNP)-based heritability was estimated to be 8.5% (s.e. = 0.004) and partitioned heritability was enriched in the central nervous system and brain tissues. Genetic correlation analysis showed shared genetic backgrounds between occupational attainment and multiple traits, including education, intelligence, leisure activities, life satisfaction, and neuropsychiatric disorders. In two-sample Mendelian randomization (MR) analysis, we demonstrated that high occupation levels were associated with reduced risk for Alzheimer's disease (OR = 0.78, 95% CI = 0.65-0.92 in inverse variance weighted (IVW) method; OR = 0.73, 95% CI = 0.57-0.92 in the weighted median (WM) method). This causal relationship between occupational attainment and Alzheimer's disease was robust in additional sensitivity analysis that excluded potentially pleiotropic SNPs (OR = 0.72, 95% CI = 0.57-0.91 in the IVW method; OR = 0.72, 95% CI = 0.53-0.97 in the WM method). Multivariable MR confirmed that occupational attainment had an independent effect on the risk for Alzheimer's disease even after taking educational attainment into account (OR = 0.72, 95% CI = 0.54-0.95 in the IVW method; OR = 0.68, 95% CI = 0.48-0.97 in the WM method). Overall, our analyses provide insights into the genetic architecture of occupational attainment and demonstrate that occupational attainment is a potential causal protective factor for Alzheimer's disease as a proxy marker of cognitive reserve.

Loneliness, Sense of Control, and Risk of Dementia in Healthy Older Adults: A Moderated Mediation Analysis

Objectives: Despite the rising prevalence of dementia, little research has been conducted to identify modifiable psychological factors that alleviate the risk of dementia in older adults and the underlying mechanisms. Given that loneliness is, in part, concomitant with a weakened sense of control, we examined whether sense of control would mediate the relation between loneliness and dementia risk. Further, considering that working -memory capacity is a critical cognitive resource that serves as a buffer against age-related cognitive decline, we examined a second-order moderated mediational model whereby working-memory capacity moderates the relation between control beliefs and dementia risk in older adults.

METHODS

We administered a series of measures to older community-dwelling adults (ages 60-93; N = 69), including the participant-rated AD8 to assess the risk of dementia. Using the PROCESS macro, we examined the moderated mediation model for the relation between loneliness, sense of control, and dementia risk.

RESULTS

We found that sense of control significantly mediated the relation between loneliness and risk of dementia. Moreover, the indirect effect of loneliness on dementia risk via lowered sense of control was significant only in individuals with poorer working-memory capacity. Notably, these findings held true when important covariates were controlled for.

CONCLUSIONS

Our findings underscore the critical role of control beliefs and working memory in protecting against dementia risk.

CLINICAL IMPLICATIONS

Our findings have implications for intervention programs that target alleviating dementia risk and promoting healthy aging in older adults by improving socioemotional health and cognitive functioning.

Cognitive reserve and the effects of virtual reality-based cognitive training on elderly individuals with mild cognitive impairment and normal cognition

BACKGROUND

Cognitive reserve (CR) is a concept proposed to account for discrepancies between the extent of brain pathology and clinical manifestations of that pathology. This study aimed to explore the associations between CR and the effects of cognitive training using fully immersive virtual reality (VR).

METHODS

A total of 44 older adults (22 cognitively normal, 22 with mild cognitive impairment) underwent eight cognitive training sessions using VR for a period of 4 weeks. CR was assessed using the Cognitive Reserve Index questionnaire (CRIq). To evaluate baseline cognitive function and the effects of VR training, the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery was administered to all participants before and after the training.

RESULTS

Greater improvement in the total CERAD score was seen for cognitively normal participants with higher versus lower scores on the Education subdomain of the CRIq. Among patients with mild cognitive impairment, none of the CRIq subdomain scores (Education, Working Activity, Leisure Time) were related to a change in CERAD total scores. The CRIq total score did not predict the improvement of global cognition in either group.

CONCLUSIONS

This study revealed different impacts of CR on cognitive training according to the participants' cognitive status. It also suggests that employing three proxies of CR rather than using a composite score would provide a more accurate understanding of one's CR.

Cognitive Reserve in Individuals Aging With Traumatic Brain Injury: Independent and Interactive Effects on Cognitive Functioning

OBJECTIVE

To examine the influence of 2 temporal factors-age and injury chronicity-on the relationship between cognitive reserve (CR) and cognitive functioning in older adults with chronic traumatic brain injury (TBI).

SETTING

Outpatient research laboratory.

PARTICIPANTS

Adults, 50 years or older, with a 1- to 45-year history of moderate or severe TBI (N = 108).

DESIGN

Cross-sectional observational study.

MAIN MEASURES

CR was estimated using demographically corrected performance on a word-reading test (an approximation of premorbid IQ). Injury chronicity was operationalized as number of years since the date of injury. Composite cognitive scores were computed from performances on neuropsychological tests of processing speed, executive functioning, and memory.

RESULTS

CR was positively and significantly related to all cognitive performances independent of age, injury chronicity, and injury severity. Greater injury chronicity significantly attenuated the effect of CR on processing speed such that individuals more distal from their injury date evidenced a weaker positive relationship between CR and performance.

CONCLUSION

Temporal factors may modify associations between CR and cognition. Findings suggest that the protective effects of CR are temporally delimited, potentially contending with declines in brain reserve. The prognostic value of traditional outcome determinants should be considered in the context of injury chronicity.