A Novel Computational Proxy for Characterizing Cognitive Reserve in Alzheimer's Disease

BACKGROUND

Although the abnormal depositions of amyloid plaques and neurofibrillary tangles are the hallmark of Alzheimer's disease (AD), converging evidence shows that the individual's neurodegeneration trajectory is regulated by the brain's capability to maintain normal cognition.

OBJECTIVE

The concept of cognitive reserve has been introduced into the field of neuroscience, acting as a moderating factor for explaining the paradoxical relationship between the burden of AD pathology and the clinical outcome. It is of high demand to quantify the degree of conceptual cognitive reserve on an individual basis.

METHODS

We propose a novel statistical model to quantify an individual's cognitive reserve against neuropathological burdens, where the predictors include demographic data (such as age and gender), socioeconomic factors (such as education and occupation), cerebrospinal fluid biomarkers, and AD-related polygenetic risk score. We conceptualize cognitive reserve as a joint product of AD pathology and socioeconomic factors where their interaction manifests a significant role in counteracting the progression of AD in our statistical model.

RESULTS

We apply our statistical models to re-investigate the moderated neurodegeneration trajectory by considering cognitive reserve, where we have discovered that 1) high education individuals have significantly higher reserve against the neuropathology than the low education group; however, 2) the cognitive decline in the high education group is significantly faster than low education individuals after the level of pathological burden increases beyond the tipping point.

CONCLUSION

We propose a computational proxy of cognitive reserve that can be used in clinical routine to assess the progression of AD.

Numeracy Skills, Cognitive Reserve, and Psychological Well-Being: What Relationship in Late Adult Lifespan?

Background: The capacity of understanding and manipulating numerical stimuli (i.e., numeracy) can impact decision making. This investigation was conducted to examine whether number comprehension and mental calculation predict hedonic (i.e., Scale of Positive and Negative Experience, SPANE) and eudaimonic (i.e., Flourishing Scale) well-being in late adulthood, and whether cognitive reserve (i.e., education, time spent for gardening, and time spent for leisure activities) and non-verbal reasoning predict numeracy skills of old adults. Additionally, the effect of age on numeracy was examined, controlling for the effect of education and cognitive efficiency. Methods: One hundred and fifty-eight (i.e., 65–94 years old) community-dwellers completed a battery of tools assessing numeracy, cognitive and metacognitive efficiency, and psychological well-being. Results: Number comprehension, metacognition, time spent for leisure, and perceived physical health accounted for 23% of the variance in the SPANE condition, whereas metacognition, perceived physical health, time for leisure, and education explained 15% of the variance in the Flourishing condition. Moreover, cognitive reserve assessed in terms of vocabulary and education predicted mental calculation. Finally, aging significantly impacted the mental calculation performance of older participants. Conclusions: These findings suggest that numeracy skills can selectively impact the mental health and daily life of older adults.

Education Moderates the Relation Between APOE ɛ4 and Memory in Nondemented Non-Hispanic Black Older Adults

BACKGROUND

The APOEɛ4 allele is a well-known risk factor for Alzheimer's disease (AD). Previous research argues that higher education helps to preserve cognition in older adults with AD pathology because of its key role in cognitive reserve and resilience.

OBJECTIVE

To test if higher educational level buffers the effect of APOEɛ4 on cognition among older non-Hispanic Blacks.

METHODS

Participants were 849 non-demented older non-Hispanic Blacks (38.3% APOEɛ4+), who underwent a comprehensive neuropsychological evaluation. Multiple linear regression models tested the relationship between APOEɛ4 status and twelve cognitive measures with education (up to high school and beyond high school) as a moderator.

RESULTS

Education buffered the effects of the APOEɛ4 allele, such that there was no impact of APOEɛ4 status on word-list memory retention and working memory among participants with more than a high school degree. This pattern was not observed for ten other cognitive measures of verbal and visual episodic memory, semantic memory, executive function, and processing speed-although a similar trend was observed for switching ability in executive functioning. The buffering effect of education was stronger among women than men.

CONCLUSION

Our findings suggest that genetic effects on late-life cognition may be modified by environmental factors such as educational attainment. These results are consistent with the framework of cognitive reserve such that engaging in cognitively enriching activities and acquiring skills and knowledge with more years of education may increase the capacity to maintain cognitive function despite high genetic risk for impairment.

Theoretical frameworks and approaches used within the Reserve, Resilience and Protective Factors professional interest area of the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment

INTRODUCTION

Reserve, resilience, maintenance, and related concepts are intensely debated in aging and Alzheimer's disease research.

METHODS

Through a short survey, we gathered information about theoretical concepts and methodologies used among research groups of the Reserve, Resilience, and Protective Factors Professional Interest Area of the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment.

RESULTS

Overall 53 research groups responded. Reserve and resilience were the most frequently used conceptual frameworks. Education, occupation, leisure, and social activities were frequently used as measures, as were longitudinal designs. Neuropsychological assessments were almost universal, and usage of imaging biomarkers was frequent. In observational-epidemiological study designs, resilience and reserve together (vs reserve alone) were commonly used as theoretical frameworks.

DISCUSSION

We provide a first description of concepts and methodologies used among reserve and resilience researchers. This will inform initiatives aiming to reach consensus on terminology and applications to establish common definitions.

"Influence of modifiable and non-modifiable variables on functioning in bipolar disorder: a path analytical study"

OBJECTIVE

The aim of this study was to investigate the influence of modifiable (mood, cognitive reserve, cognitive performance) and non-modifiable factors (diagnosis, suicide attempts, substance use, age) on self-reported functioning in BD.

METHODS

103 adults with no mood disorders and 95 individuals with BD completed the WHODAS 2.0, in addition to a neuropsychological battery and diagnostic assessments. Path analysis was then used to analyse the relationships between modifiable and non-modifiable predictors of functioning in the sample.

RESULTS

Cognitive reserve and age had an indirect influence on individual functioning, mediated by cognitive performance. The influence of diagnosis and depressive symptoms on functioning was partly direct, and partly mediated by cognition. The presence of psychiatric comorbidities in addition to BD also had a significant influence on individual functioning.

CONCLUSIONS

Initiatives focussed on modifiable factors such as depressive symptoms and cognitively stimulating activities, which increase cognitive reserve, may be a useful complement to existing treatments and help patients achieve functional recovery. KEY POINTS Individual functioning was influenced by cognitive performance, cognitive reserve, age, diagnosis and depressive symptoms. Executive functioning mediated the influence of age and cognitive reserve on individual functioning. Interventions focussed on depressive symptoms and cognitive stimulation may help patients achieve functional recovery.

Role of cognitive reserve in cognitive variability in euthymic individuals with bipolar disorder: cross-sectional cluster analysis

BACKGROUND

People with bipolar disorder have moderate cognitive difficulties that tend to be more pronounced during mood episodes but persist after clinical remission and affect recovery. Recent evidence suggests heterogeneity in these difficulties, but the factors underlying cognitive heterogeneity are unclear.

AIMS

To examine whether distinct cognitive profiles can be identified in a sample of euthymic individuals with bipolar disorder and examine potential differences between subgroups.

METHOD

Cognitive performance was assessed across four domains (i.e. processing speed, verbal learning/memory, working memory, executive functioning) in 80 participants. We conducted a hierarchical cluster analysis and a discriminant function analysis to identify cognitive profiles and considered differences in cognitive reserve, estimated cognitive decline from premorbid cognitive functioning, and clinical characteristics among subgroups.

RESULTS

Four discrete cognitive profiles were identified: cognitively intact (n = 25; 31.3%); selective deficits in verbal learning and memory (n = 15; 18.8%); intermediate deficits across all cognitive domains (n = 30; 37.5%); and severe deficits across all domains (n = 10; 12.5%). Cognitive decline after illness onset was greater for the intermediate and severe subgroups. Cognitive reserve scores were increasingly lower for subgroups with greater impairments. A smaller proportion of cognitively intact participants were using antipsychotic medications compared with all other subgroups.

CONCLUSIONS

Our findings suggest that individuals with cognitively impaired profiles demonstrate more cognitive decline after illness onset. Cognitive reserve may be one of the factors underlying cognitive variability across people with bipolar disorder. Patients in the intermediate and severe subgroups may be in greater need of interventions targeting cognitive difficulties.

Impact of Cognitive Reserve and Structural Connectivity on Cognitive Performance in Multiple Sclerosis

Background: Cognitive reserve (CR) could attenuate the impact of the brain burden on the cognition in people with multiple sclerosis (PwMS).

Objective: To explore the relationship between CR and structural brain connectivity and investigate their role on cognition in PwMS cognitively impaired (PwMS-CI) and cognitively preserved (PwMS-CP).

Methods: In this study, 181 PwMS (71% female; 42.9 ± 10.0 years) were evaluated using the Cognitive Reserve Questionnaire (CRQ), Brief Repeatable Battery of Neuropsychological tests, and MRI. Brain lesion and gray matter volumes were quantified, as was the structural network connectivity. Patients were classified as PwMS-CI (z scores = −1.5 SD in at least two tests) or PwMS-CP. Linear and multiple regression analyses were run to evaluate the association of CRQ and structural connectivity with cognition in each group. Hedges's effect size was used to compute the strength of associations.

Results: We found a very low association between CRQ scores and connectivity metrics in PwMS-CP, while in PwMS-CI, this relation was low to moderate. The multiple regression model, adjusted for age, gender, mood, lesion volume, and graph metrics (local and global efficiency, and transitivity), indicated that the CRQ (β = 0.26, 95% CI: 0.17–0.35) was associated with cognition (adj R² = 0.34) in PwMS-CP (55%). In PwMS-CI, CRQ (β = 0.18, 95% CI: 0.07–0.29), age, and network global efficiency were independently associated with cognition (adj R² = 0.55). The age- and gender-adjusted association between CRQ score and global efficiency on having an impaired cognitive status was −0.338 (OR: 0.71, p = 0.036) and −0.531 (OR: 0.59, p = 0.002), respectively.

Conclusions: CR seems to have a marginally significant effect on brain structural connectivity, observed in patients with more severe clinical impairment. It protects PwMS from cognitive decline regardless of their cognitive status, yet once cognitive impairment has set in, brain damage and aging are also influencing cognitive performance.

Moderation-Mediation Effects in Bilingualism and Cognitive Reserve

We first provide a critical review of the existing findings on bilingualism as a contributor to cognitive reserve from moderator-mediator warranting cause-effect research conclusions. We next address the question of direct or indirect effects between bilingualism and neurocognitive protective factors influencing the associated age-related mental deficits. The existing findings support bilingualism as a predictor and as a moderator. Third, we propose cognitive reserve models of bilingualism describing analytical approaches that allow testing of these models and hypotheses related to path strength and causal relationships between predictors, moderators, and mediators. Lastly and most importantly, we suggest using large datasets available via open repositories. This can aid in the testing of theoretical models, clarifying the roles of moderators and mediators, and assessing the research viability of multi-causal paths that can influence cognitive reserve. Creating collaborative datasets to test these models would greatly advance our field and identify critical variables in the study of the bilingual aging brain.

Cognitive Reserve, Leisure Activity, and Neuropsychological Profile in the Early Stage of Cognitive Decline

In older adults with normal cognition, cognitive reserve (CR) is known to be associated with the neuropsychological profile. We investigated the association between comprehensive CR and detailed neuropsychological profile in the early stage of cognitive decline. Fifty-five participants with mild cognitive impairment or subjective cognitive decline completed the cognitive reserve index questionnaire (CRIq) that yielded total, education, working activity, and leisure time scores (CRI-Total, CRI-Education, CRI-Working activity, and CRI-Leisure time, respectively). Mini-mental state examination (MMSE) and detailed neuropsychological evaluation were performed. Psychiatric symptom scales were applied to measure depression, apathy, positive or negative affect, and quality of life. Correlation and linear regression analyses of the variables were performed. The effect of CR-Education, CRI-Working activity, and CRI-Leisure time on the composite cognitive score was determined using a multivariable regression model. We observed that for CRI-Total (B = 3.00, p = 0.005), CRI-Education (B = 3.39, p = 0.002), and CRI-Leisure time (B = 2.56, p = 0.015), CR correlated with MMSE scores, while only CRI-Leisure time associated with the naming ability (B = 2.20, p = 0.033) in the detailed neuropsychological test results of the participants. Multivariable regression model also indicated that among CRI subscores, CRI-Leisure time directly affects the composite cognitive score (β = 0.32, p = 0.011). We found that in the early stage of cognitive decline in older adults, comprehensive CR was associated with global cognition, and only leisure activity was identified to be associated with the detailed neuropsychological profile including naming ability. These results may imply the positive effect of leisure activity on cognitive function in the early stages of cognitive decline.

Right Lateralized Brain Reserve Offsets Age-Related Deficits in Ignoring Distraction

Age-related deterioration of attention decreases the ability to stay focused on the task at hand due to less efficient selection of relevant information and increased distractibility in the face of irrelevant, but salient stimuli. While older (compared with younger) adults may have difficulty suppressing salient distractors, the extent of these challenges differs vastly across individuals. Cognitive reserve measured by proxies of cognitively enriching life experiences, such as education, occupation, and leisure activities, is thought to mitigate the effects of the aging process and account for variability in trajectories of cognitive decline. Based on combined behavioral and neuroimaging (voxel-based morphometry) analyses of demographic, cognitive, and neural markers of aging and cognitive reserve proxy measures, we examine here predictors of variability in the age-related changes in attention function, indexed by ability to suppress salient distraction. Our findings indicate that in healthy (neurotypical), aging gray matter volume within several right lateralized fronto-parietal brain regions varies according to both levels of cognitive reserve (education) and the capacity to effectively select visual stimuli amid salient distraction. Thus, we provide here novel experimental evidence supporting Robertson's theory of a right lateralized neural basis for cognitive reserve.

PER2 C111G polymorphism, cognitive reserve and cognition in subjective cognitive decline and mild cognitive impairment: a 10-year follow-up study

BACKGROUND AND PURPOSE

CLOCK and PER2 genes have been implicated in sleep-wake cycle alterations and neurodegenerative diseases. Our aim was to evaluate the effect of CLOCK T3111C and PER2 C111G on cognitive functioning in subjective cognitive decline (SCD) patients and mild cognitive impairment (MCI) patients at the baseline of a longitudinal study, and the effect of these two polymorphisms on the progression to Alzheimer's disease (AD) of the two groups.

METHODS

Sixty-eight subjects (41 SCD and 27 MCI) who underwent clinical evaluation, neuropsychological assessment, CLOCK and PER2 genotyping at baseline and neuropsychological follow-up every 2 years for a mean time of 10 years were included. Subjects who developed AD (SCD-c and MCI-c) and non-converters (SCD-nc, MCI-nc) were considered.

RESULTS

CLOCK T3111C was detected in 47% of cases (21 SCD, 11 MCI) and PER2 C111G in 19% of cases (eight SCD and five MCI). PER2 G carriers presented lower premorbid intelligence score (P = 0.049), fewer years of education (P = 0.007) and a lower frequency of family history of AD (P = 0.04) than G non-carriers. MCI PER2 G carriers had worse performance in tests assessing memory, executive function, language and visuospatial abilities at baseline. During follow-up, two SCD and 15 MCI subjects progressed to AD: both of the SCD-c subjects presented the PER2 G allele, while none of the SCD PER2 G non-carriers converted to AD (P = 0.003).

CONCLUSION

PER2 seems to have a role in cognitive reserve and cognition in SCD and MCI patients. Nevertheless, further studies are needed to assess the role of PER2 C111G on the risk of progression to AD.

Physical Activity and Trajectories of Cognitive Change in Community-Dwelling Older Adults: The Rancho Bernardo Study

BACKGROUND

Although physical activity has been associated with better cognitive function and reduced dementia risk, its association with cognitive decline in normal aging remains uncertain.

OBJECTIVE

To determine whether physical activity in youth and older age are associated with age-related cognitive change.

METHODS

Over a period of 27 years, 2,027 community-dwelling adults (mean age 73.5; 60% women) of the Rancho Bernardo Study of Healthy Aging completed up to seven cognitive assessments, including tests of global cognitive function, executive function, verbal fluency, and episodic memory. At each visit, participants reported concurrent physical activity. At baseline (1988- 1992), participants additionally reported physical activity as a teenager and at age 30. For each age period, participants were classified as regularly active (3+ times/week) or inactive.

RESULTS

Associations between concurrent physical activity and better cognitive function were stronger with advancing age on all tests, even after accounting for education, health, and lifestyle factors, as well as survival differences (ps < 0.05). Baseline physical activity did not predict rates of cognitive decline (ps > 0.40). Individuals who were physically active at age 30 and older age maintained the highest global cognitive function with advancing age (p = 0.002).

CONCLUSION

Regular physical activity is associated with better cognitive function with advancing age. Physical activity in young adulthood may contribute to cognitive reserve, which together with physical activity in later years, may act to preserve cognitive function with age.

Social Isolation and Cognitive Function in Later Life: A Systematic Review and Meta-Analysis

BACKGROUND

There is some evidence to suggest that social isolation may be associated with poor cognitive function in later life. However, findings are inconsistent and there is wide variation in the measures used to assess social isolation.

OBJECTIVE

We conducted a systematic review and meta-analysis to investigate the association between social isolation and cognitive function in later life.

METHODS

A search for longitudinal studies assessing the relationship between aspects of social isolation (including social activity and social networks) and cognitive function (including global measures of cognition, memory, and executive function) was conducted in PsycInfo, CINAHL, PubMed, and AgeLine. A random effects meta-analysis was conducted to assess the overall association between measures of social isolation and cognitive function. Sub-analyses investigated the association between different aspects of social isolation and each of the measures of cognitive function.

RESULTS

Sixty-five articles were identified by the systematic review and 51 articles were included in the meta-analysis. Low levels of social isolation characterized by high engagement in social activity and large social networks were associated with better late-life cognitive function (r = 0.054, 95% CI: 0.043, 0.065). Sub-analyses suggested that the association between social isolation and measures of global cognitive function, memory, and executive function were similar and there was no difference according to gender or number of years follow-up.

CONCLUSIONS

Aspects of social isolation are associated with cognitive function in later life. There is wide variation in approaches to measuring social activity and social networks across studies which may contribute to inconsistencies in reported findings.

Cognitive Persistence and Executive Function in the Multilingual Brain During Aging

Researchers have debated the extent to which the experience of speaking more than two languages induces long-term neuroplasticity that protects multilinguals from the adverse cognitive effects of aging. In this review, I propose a novel theory that multilingualism affects cognitive persistence, the application of effort to improve performance on challenging tasks. I review recent evidence demonstrating that the cingulo-opercular network, consisting of the bilateral inferior frontal gyrus (IFG) and dorsal anterior cingulate cortex (dACC), supports cognitive persistence. I then show that this same network is involved in multilingual language control and changes with multilingual language experience. While both early and late multilinguals exhibit differences in the cingulo-opercular network compared to monolinguals, I find that early multilinguals have a pattern of decreased dACC activity and increased left IFG activity that may enable more efficient cognitive control, whereas late multilinguals show larger dACC responses to conflict that may be associated with higher cognitive persistence. I further demonstrate that multilingual effects on the cingulo-opercular network are present in older adults and have been implicated in the mitigation of cognitive symptoms in age-related neurodegenerative disorders. Finally, I argue that mixed results in the literature are due, in part, to the confound between cognitive persistence and ability in most executive function tasks, and I provide guidance for separating these processes in future research.

Association between cognitive reserve dimensions and frailty among older adults: A structured narrative review

Frailty is a broadly investigated geriatric condition, which is characterized by an increased vulnerability to stressors. It represents an extremely relevant public health issue, increasingly conceptualized in a multidimensional perspective. The concept of cognitive reserve (CR), as originally conceptualized by Stern, has been developed in the past decades as a potential factor able to determine individual differences in cognitive vulnerability and trajectories occurring with aging. Our purpose was to provide a comprehensive review of the literature exploring the relationship between CR dimensions, selected according to the Stern model, and frailty status. A review of the literature on the association between potential CR dimensions and frailty was carried out through PubMed, Web of Knowledge and Scopus. CR expressed in terms of education, occupation, premorbid intelligence quotient and leisure time activities was associated with frailty in both cross-sectional and longitudinal observations. The majority of reviewed evidence suggests a potential protective role of CR factors against the onset and the worsening of frailty among older adults. To the best of our knowledge, this is the first attempt to provide a comprehensive overview regarding the association between CR dimensions and frailty. Education, occupation, premorbid intelligence quotient and leisure time activities are able to interact with the general concept of frailty, rather than simply affecting the cognitive trajectory towards dementia. The lack of a unique and operationalized approach to the assessment of CR, as well as the wide heterogeneity of frailty evaluation tools and criteria, denote some methodological critical issues that need to be overcome. Geriatr Gerontol Int 2020; 20: 1005-1023..

Subjective Cognitive Decline, Cognitive Reserve Indicators, and the Incidence of Dementia

OBJECTIVE

Both cognitive reserve and subjective cognitive decline are closely related to the risk of dementia. We investigated whether cognitive reserve can modify the risk of dementia developing from subjective cognitive decline.

DESIGN

Longitudinal population-based study.

SETTING AND PARTICIPANTS

The prospective study analyzed data from 2099 participants aged 65 or over from the Cognitive Function and Ageing Study-Wales (CFAS-Wales).

METHODS

Dementia was ascertained through the comprehensive judgment symptoms of geriatric mental state automated geriatric examination for computer assisted taxonomy (GMS-AGECAT). Subjective cognitive decline was evaluated by 2 questions in the baseline interview. Cognitive reserve indicators were derived from 3 previously identified factors: early life education, mid-life occupational complexity, and late-life cognitive activities. We used logistic regression models to estimate dementia risk in relation to subjective cognitive decline and indicators of cognitive reserve. The interaction between subjective cognitive decline and cognitive reserve were evaluated by additive and multiplicative scales.

RESULTS

Baseline subjective cognitive decline and low cognitive reserve significantly increased the risk of dementia, after 2 years of follow-up. There was an additive interaction between subjective cognitive decline and cognitive reserve [the relative excess risk due to interaction = -0.63, 95% confidence interval (CI) = -0.89 to -0.36, P for additive interaction <0.001]. There was no multiplicative interaction between subjective cognitive decline and cognitive reserve indicator (P = .138). Statistically significant association between subjective cognitive decline and dementia was found only in the low-level and medium-level cognitive reserve group (OR = 3.78, 95% CI = 1.50-9.55 and OR = 3.64, 95% CI = 1.09-12.2, respectively), but not in the high-level groups.

CONCLUSION AND IMPLICATIONS

Cognitive reserve attenuated subjective cognitive decline associated risk of developing dementia. This finding suggests the need for greater emphasis on detecting prodromal dementia when older patients having lower cognitive reserve present with subjective cognitive decline.

Strategy or symptom: Semantic clustering and risk of Alzheimer's disease-related impairment

Alzheimer's disease (AD) is the most common form of dementia, impacting global cognitive performance, including episodic memory. Semantic clustering is a learning strategy involving grouping words of similar meaning and can improve episodic memory performance, e.g., list learning. As the APOE ε4 allele is the most validated genetic risk factor for AD, we predicted that its presence would be associated with poorer list learning performance, and we hypothesized that semantic clustering moderates or mediates this association. The sample comprised 699 healthy older adults participating in the CHARIOT PRO Main Study, 169 of whom were APOE ε4 carriers. Participants' ability to form groups of related stimuli (assessed via a categorization task, CAT), and their use of semantic clustering during list learning, were investigated using the Neuropsychological Assessment Battery (NAB). CAT scores predicted the use of semantic clustering in, and performance on, the list learning task. CAT scores were not significantly lower in APOE ε4 carriers, suggesting that the ability to categorize was preserved. However, APOE ε4 carriers made less use of semantic clustering in list learning. Semantic clustering use partially mediated the relationship between CAT scores and list learning performance, and, in women only, moderated the impact of APOE ε4 on list learning performance. The results suggest that better categorization ability is associated with greater use of mnemonic strategies and better performance on memory tasks regardless of genetic risk, but that APOE ε4 carriers make less use of such strategies. Furthermore, female APOE ε4 carriers may benefit more than their non-carriers from using semantic clustering to aid list learning. Thus, semantic clustering may be a contributing factor of their "cognitive reserve", compensating for potential deficits in episodic memory.

Cognitive profiles in obstructive sleep apnea: a cluster analysis in sleep clinic and community samples

STUDY OBJECTIVES

Although cognitive dysfunction is a recognized consequence of untreated obstructive sleep apnea (OSA), the deficit pattern is heterogeneous. Understanding this heterogeneity may identify those at risk of cognitive deficits and guide intervention strategies. To facilitate understanding, we examined whether distinct profiles of neuropsychological performance were present in OSA and, if so, how they are related to other OSA features.

METHODS

We studied sleep clinic (n = 121) and community (n = 398) samples with moderate-severe OSA (apnea-hypopnea index ≥ 15 events/h). Attention and memory were assessed using the Cognitive Drug Research system. Sleep was assessed using polysomnography in the clinic sample and dual channel (flow, oximetry) portable monitoring in the community sample. Latent profile analysis was used to determine structure of cognitive clusters. Discriminant function analysis was used to examine associations between nocturnal and diurnal features of OSA and profile membership.

RESULTS

Both samples were best characterized by a 3-profile solution: (1) strong thinkers (performed well across most domains and showed greater cognitive reserve); (2) inattentive fast thinkers (strong processing speed but poor ability to maintain attention); and (3) accurate slow thinkers (strengths in maintaining attention but poor processing speed). Profile membership was associated with mean overnight oxygen saturation and cognitive reserve in the clinic sample and the presence of cardiovascular disease and/or diabetes in the community sample.

CONCLUSIONS

These findings help explain the diversity of outcomes in previous studies of cognitive dysfunction in OSA by demonstrating that individual differences in cognitive reserve, nocturnal oxygen saturation, and comorbidities affect how cognition is impacted by OSA.

The temporal stability of premorbid intelligence: A non-clinical 10-year follow-up study using the Irregular Word Reading Test (TeLPI)

INTRODUCTION

The Cognitive Reserve (CR) describes the brain's ability to actively cope with neurological damage, enabling the maintenance of premorbid cognitive functioning through compensatory processes. The most common way to estimate CR is through formal education, the intelligence quotient (IQ) and participation in cognitive stimulating activities. In the absence of IQ data, the Irregular Word Reading Test (TeLPI) allows you to estimate the premorbid intelligence.

OBJECTIVE

The comparison of the TeLPI results between two times of assessment (baseline and re-assessment) with an interval time (IT) of 9 years. To analyze of the stability of their results as a valid dimension for the CR estimation.

RESULTS

The TeLPI presented temporal stability of its results between the two evaluation times (IT = 9.07 ± 1.02). The sample, composed by 63 cognitively healthy participants, showed no differences for the estimated Full Scale IQ (t(62) = 0.49, p = .63), for the Estimated Verbal IQ (t(62) = 0.71, p = .48) and for the estimated Performance IQ (t(62) = 0.64, p = .52). Likewise, no differences were found in the number of TeLPI errors at the two assessment times (t(62) = -0.61, p = .54).

CONCLUSIONS

Considering that CR is characterized as being relatively stable, the TeLPI should be included in its assessment, as an indicator with proved stability over a long period of time, on the physiological aging spectrum.

Identifying Mechanisms of Normal Cognitive Aging Using a Novel Mouse Genetic Reference Panel

Developing strategies to maintain cognitive health is critical to quality of life during aging. The basis of healthy cognitive aging is poorly understood; thus, it is difficult to predict who will have normal cognition later in life. Individuals may have higher baseline functioning (cognitive reserve) and others may maintain or even improve with age (cognitive resilience). Understanding the mechanisms underlying cognitive reserve and resilience may hold the key to new therapeutic strategies for maintaining cognitive health. However, reserve and resilience have been inconsistently defined in human studies. Additionally, our understanding of the molecular and cellular bases of these phenomena is poor, compounded by a lack of longitudinal molecular and cognitive data that fully capture the dynamic trajectories of cognitive aging. Here, we used a genetically diverse mouse population (B6-BXDs) to characterize individual differences in cognitive abilities in adulthood and investigate evidence of cognitive reserve and/or resilience in middle-aged mice. We tested cognitive function at two ages (6 months and 14 months) using y-maze and contextual fear conditioning. We observed heritable variation in performance on these traits (h 2 RIx̄ = 0.51-0.74), suggesting moderate to strong genetic control depending on the cognitive domain. Due to the polygenetic nature of cognitive function, we did not find QTLs significantly associated with y-maze, contextual fear acquisition (CFA) or memory, or decline in cognitive function at the genome-wide level. To more precisely interrogate the molecular regulation of variation in these traits, we employed RNA-seq and identified gene networks related to transcription/translation, cellular metabolism, and neuronal function that were associated with working memory, contextual fear memory, and cognitive decline. Using this method, we nominate the Trio gene as a modulator of working memory ability. Finally, we propose a conceptual framework for identifying strains exhibiting cognitive reserve and/or resilience to assess whether these traits can be observed in middle-aged B6-BXDs. Though we found that earlier cognitive reserve evident early in life protects against cognitive impairment later in life, cognitive performance and age-related decline fell along a continuum, with no clear genotypes emerging as exemplars of exceptional reserve or resilience - leading to recommendations for future use of aging mouse populations to understand the nature of cognitive reserve and resilience.

The role of cognitive reserve in the relationship between metabolic syndrome and cognitive functioning

Metabolic syndrome (MetS) is a cluster of vascular risk factors that can impact cognition. Cognitive reserve (CR), specifically early operators of reserve (e.g., education), have not been explored in the relationship between MetS and cognition. Adults 45-90 years old (n = 149) underwent neuropsychological testing and evaluation for MetS. Exploratory and confirmatory factor analyses defined neuropsychological domains and created a CR score based on early operators of CR. Regression analyses examined the association among MetS, CR, and neuropsychological performance. CFA revealed two neuropsychological factors: Episodic Memory and Executive Functioning. Controlling for age and physical ability, MetS and CR were significant predictors of the Factors. With CR in the model, MetS became a non-significant predictor of Executive Functioning; CR and physical ability were the most significant predictors. CR and MetS significantly predicted Episodic Memory . The results are discussed in the context of neuroprotective factors and cognitive aging.

Effects of bilingualism on age at onset in two clinical Alzheimer's disease variants

INTRODUCTION

The effect of bilingualism on age at onset has yet to be examined within different clinical variants of Alzheimer's disease.

METHODS

We reviewed the research charts of 287 well-characterized participants with either amnestic Alzheimer's dementia or logopenic variant primary progressive aphasia (lvPPA) and identified bilingual speakers based on regular use of two or more languages and/or ability to communicate with native speakers in two or more languages. We evaluated whether bilingual speakers demonstrated a delay in age of symptom onset relative to monolingual speakers while controlling for other variables known to influence cognitive reserve.

RESULTS

A 5-year delay in age at symptom onset was observed for bilingual relative to monolingual speakers with lvPPA. This delay in onset was not observed in the amnestic Alzheimer's dementia cohort.

DISCUSSION

Bilingualism may serve as a unique cognitive reserve variable in lvPPA, but not in amnestic Alzheimer's dementia.

Interaction effect of Alzheimer's disease pathology and education, occupation, and socioeconomic status as a proxy for cognitive reserve on cognitive performance: in vivo positron emission tomography study

AIM

Educational attainment, occupation, and socioeconomic status have been regarded as major factors influencing cognitive reserve (CR). This study aimed to investigate the interaction effect of amyloid-β/tau burden and education/occupation/socioeconomic status as a proxy for CR on cognitive performance.

METHODS

We analyzed the datasets of the Alzheimer's Disease Neuroimaging Initiative. We included clinically normal subjects and patients with mild cognitive impairment or Alzheimer's disease who had undergone a florbetapir scan within 1 year of a flortaucipir (AV-1451) scan (n = 127). Partial correlation analysis between the standardized uptake value ratio of florbetapir/AV-1451 and the proxy for CR was performed with the 13-item Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) score as a covariate. Stepwise multiple linear regression analysis was performed to determine the predictors of ADAS-cog performance based on the interaction between the imaging biomarkers and the proxy for CR.

RESULTS

We found a significant positive partial correlation between educational level and tau pathology in Braak stage 1/2 areas, and we observed significantly higher tau accumulation among participants with higher education when ADAS-cog score was used as a covariate. The interaction between tau and education was a good predictor of cognitive function, with higher tau accumulation showing a greater association with higher ADAS-cog score among participants with less education than among those with more education.

CONCLUSION

Our findings indicate the protective effect of education against cognitive dysfunction in early-stage Alzheimer's disease pathology and suggest that education may exert a beneficial effect by reducing the adverse cognitive consequences of tau aggregation.

Interaction between Cognitive Reserve and Biomarkers in Alzheimer Disease

Patients with comparable degree of neuropathology could show different cognitive impairments. This could be explained with the concept of cognitive reserve (CR), which includes a passive and an active component. In particular, CR is used to explain the gap between tissue damage and clinical symptoms that has been observed in dementia and, in particular, in patients affected by Alzheimer disease (AD). Different studies confirm brain neuroplasticity. Our preliminary study demonstrated that AD patients with high education showed a CR inversely associated with glucose uptake measured in fluorodeoxyglucose positron emission tomography (FDG-PET), whereas the inverse correlation was observed in AD patients with low education. In other words, our findings suggest that CR compensates the neurodegeneration and allows the maintenance of patients’ cognitive performance. Best understanding of the concept of CR could lead to interventions to slow cognitive aging or reduce the risk of dementia.

An UNC5C Allele Predicts Cognitive Decline and Hippocampal Atrophy in Clinically Normal Older Adults

BACKGROUND

The UNC5C rs3846455G allele has been linked to poor cognitive resilience against age-related neuropathologies, but this association remains to be replicated, and the allele's effect on hippocampal neurodegeneration needs to be examined.

OBJECTIVE

To further validate the association between rs3846455G and faster cognitive decline, especially among cognitively normal older adults, and to assess whether rs3846455G predicts accelerated hippocampal volume loss in older adults.

METHODS

We assessed participants in the Harvard Aging Brain Study (HABS), a longitudinal cohort study of older adults who were clinically normal at baseline. To avoid bias from population admixture, analyses were limited to participants of European descent with longitudinal neuroimaging data (n = 174). Linear mixed effect models were used to examine the effect of rs3846455G on longitudinal change of the Preclinical Alzheimer Cognitive Composite (PACC) and MRI-measured bilateral hippocampal volume, adjusting for baseline amyloid-β (Aβ) measured by the cortical Pittsburgh Compound B PET distributed volume ratio. We also tested whether hippocampal atrophy mediates the association between rs3846455G and greater PACC decline through a mediation analysis.

RESULTS

rs3846455G was associated with greater PACC decline (β= -0.087/year, 95% CI -0.169 to -0.005, p = 0.039) after controlling for baseline Aβ. Further, rs3846455G predicted accelerated hippocampal atrophy after controlling for baseline Aβ (β= -57.3 mm3/year, 95% CI -102.8 to -11.9, p = 0.014). The association between rs3846455G and greater PACC decline was partially mediated by accelerated hippocampal atrophy (mediated effect (relative scale) = -0.014, 95% CI -0.032 to -6.0×10-4, p = 0.039).

CONCLUSION

UNC5C rs3846455G predicts greater cognitive decline and accelerated hippocampal atrophy in clinically normal older adults.