Brain reserve, cognitive reserve, compensation, and maintenance: operationalization, validity, and mechanisms of cognitive resilience

Memory self-efficacy and working memory

Dementia affects multiple aspects of cognitive functioning, including working memory and executive functioning. Memory self-efficacy (MSE) has previously been related to episodic memory performance and to executive functioning, but little research has examined the relations between MSE and working memory. United States older adults (N  = 197) were recruited via MTurk to complete an MSE questionnaire before completing a digit span working memory task. Hierarchical regression results revealed that the model accounted for a significant amount of variance in working memory performance after statistically controlling for several covariates, F(11, 179) = 4.94, p < .001, adjusted R2 = .19. MSE explained a large and unique portion of variance (B = 1.02, SE = 0.17, p < .001). Based on our findings, one's beliefs about their memory are positively associated with their working memory performance. These novel findings provide support for neuropsychologists to consider using MSE measures and utilizing MSE interventions.

Age-related differences in network controllability are mitigated by redundancy in large-scale brain networks

The aging brain undergoes major changes in its topology. The mechanisms by which the brain mitigates age-associated changes in topology to maintain robust control of brain networks are unknown. Here we use diffusion MRI data from cognitively intact participants (n = 480, ages 40-90) to study age-associated differences in the average controllability of structural brain networks, topological features that could mitigate these differences, and the overall effect on cognitive function. We find age-associated declines in average controllability in control hubs and large-scale networks, particularly within the frontoparietal control and default mode networks. Further, we find that redundancy, a hypothesized mechanism of reserve, quantified via the assessment of multi-step paths within networks, mitigates the effects of topological differences on average network controllability. Lastly, we discover that average network controllability, redundancy, and grey matter volume, each uniquely contribute to predictive models of cognitive function. In sum, our results highlight the importance of redundancy for robust control of brain networks and in cognitive function in healthy-aging.

Cognitive-Cognitive Dual-task in aging: A cross-sectional online study

The prevalence of neurodegenerative disorders, particularly dementia, is on the rise across many countries worldwide. This negative trend calls for improving our understanding of cognitive aging. While motor-cognitive dual-task approaches have already been proven valuable for clinical diagnosis, comparatively less research is available on the application of Cognitive-Cognitive Dual-Tasking (CCDT), across several cognitive domains. Moreover, there is limited understanding about how healthy aging affects performance in such dual-tasks in the general population. CCDT entails engaging individuals in multiple cognitive tasks simultaneously and holds promise for remote e-Health interventions. In this cross-sectional study, our objective was to evaluate the suitability of a newly developed, self-administered, online tool for examining age-related differences in memory performance under dual-tasking. 337 healthy adults aged 50-90 underwent a visual memory test (Memo) under both single and dual-task conditions (attend to auditory letters). Additional measures included questionnaires on subjective memory complaints (MAC-Q), on cognitive reserve (CR), and a cognitive screening (auto-GEMS). As expected, the accuracy of visual memory performance exhibited a negative correlation with age and MAC-Q, and a positive correlation with CR and auto-GEMS scores. Dual-tasking significantly impaired performance, and its detrimental effect decreased with increasing age. Furthermore, the protective effect of cognitive reserve diminished with advancing age. These findings suggest that the commonly observed age-related increase in dual-task costs is not universally applicable across all tasks and cognitive domains. With further refinement, a longitudinal implementation of this approach may assist in identifying individuals with a distinct cognitive trajectory and potentially at a higher risk of developing cognitive decline.

Neuromodulatory subcortical nucleus integrity is associated with white matter microstructure, tauopathy and APOE status

The neuromodulatory subcortical nuclei within the isodendritic core (IdC) are the earliest sites of tauopathy in Alzheimer's disease (AD). They project broadly throughout the brain's white matter. We investigated the relationship between IdC microstructure and whole-brain white matter microstructure to better understand early neuropathological changes in AD. Using multiparametric quantitative magnetic resonance imaging we observed two covariance patterns between IdC and white matter microstructure in 133 cognitively unimpaired older adults (age 67.9 ± 5.3 years) with familial risk for AD. IdC integrity related to 1) whole-brain neurite density, and 2) neurite orientation dispersion in white matter tracts known to be affected early in AD. Pattern 2 was associated with CSF concentration of phosphorylated-tau, indicating AD specificity. Apolipoprotein-E4 carriers expressed both patterns more strongly than non-carriers. IdC microstructure variation is reflected in white matter, particularly in AD-affected tracts, highlighting an early mechanism of pathological development.

Influence of cognitive reserve on cognitive and motor function in α-synucleinopathies: A systematic review and multilevel meta-analysis

Cognitive reserve has shown promise as a justification for neuropathologically unexplainable clinical outcomes in Alzheimer's disease. Recent evidence suggests this effect may be replicated in conditions like Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. However, the relationships between cognitive reserve and different cognitive abilities, as well as motor outcomes, are still poorly understood in these conditions. Additionally, it is unclear whether the reported effects are confounded by medication. This review analysed studies investigating the relationship between cognitive reserve and clinical outcomes in these α-synucleinopathy cohorts, identified from MEDLINE, Scopus, psycINFO, CINAHL, and Web of Science. 85 records, containing 176 cognition and 31 motor function effect sizes, were pooled using multilevel meta-analysis. There was a significant, positive association between higher cognitive reserve and both better cognition and motor function. Cognition effect sizes differed by disease subtype, cognitive reserve measure, and outcome type; however, no moderators significantly impacted motor function. Review findings highlight the clinical implications of cognitive reserve and importance of engaging in reserve-building behaviours.

Trajectories of Occupational Cognitive Demands and Risk of Mild Cognitive Impairment and Dementia in Later Life: The HUNT4 70+ Study

BACKGROUND AND OBJECTIVES

The cognitive reserve hypothesis posits that cognitively stimulating work delays the onset of mild cognitive impairment (MCI) and dementia. However, the effect of occupational cognitive demands across midlife on the risk of these conditions is unclear.

METHODS

Using a cohort study design, we evaluated the association between registry-based trajectories of occupational cognitive demands from ages 30-65 years and clinically diagnosed MCI and dementia in participants in the HUNT4 70+ Study (2017-19). Group-based trajectory modeling identified trajectories of occupational cognitive demands, measured by the routine task intensity (RTI) index (lower RTI indicates more cognitively demanding occupation) from the Occupational Information Network. Multinomial regression was implemented to estimate the relative risk ratios (RRRs) of MCI and dementia, after adjusting for age, sex, education, income, baseline hypertension, obesity, diabetes, psychiatric impairment, hearing impairment, loneliness, smoking status, and physical inactivity assessed at HUNT1-2 in 1984-1986 and 1995-1997. To handle missing data, we used inverse probability weighting to account for nonparticipation in cognitive testing and multiple imputation.

RESULTS

Based on longitudinal RTI scores for 305 unique occupations, 4 RTI trajectory groups were identified (n = 7,003, 49.8% women, age range 69-104 years): low RTI (n = 1,431, 20.4%), intermediate-low RTI (n = 1,578, 22.5%), intermediate-high RTI (n = 2,601, 37.1%), and high RTI (n = 1,393, 19.9%). Participants in the high RTI group had a higher risk of MCI (RRR 1.74, 95% CI 1.41-2.14) and dementia (RRR 1.37, 95% CI 1.01-1.86), after adjusting for age, sex, and education compared with participants in the low RTI group. In a sensitivity analysis, controlling for income and baseline health-related factors, the point estimates were not appreciably changed (RRR 1.66, 95% CI 1.35-2.06 for MCI, and RRR 1.31, 95% CI 0.96-1.78 for dementia).

DISCUSSION

People with a history of cognitively stimulating occupations during their 30s, 40s, 50s, and 60s had a lower risk of MCI and dementia older than 70 years, highlighting the importance of occupational cognitive stimulation during midlife for maintaining cognitive function in old age. Further research is required to pinpoint the specific occupational cognitive demands that are most advantageous for maintaining later-life cognitive function.

Evaluating the Stroop Test With Older Adults: Construct Validity, Short Term Test-Retest Reliability, and Sensitivity to Mental Fatigue

We conducted two studies to evaluate the construct validity, short term test-retest reliability, and sensitivity to mental fatigue of the Stroop task when used with older adults. In Study 1, 40 participants visited our lab on two separate days. On the first visit, they took five screening scales, and we measured their height and body mass. On the second visit, they completed the Stroop task twice with a 30-minute interval between assessments. In Study 2, 15 different participants took a 30-minute Flanker/Reverse Flanker task during the interval between the two administrations of the Stroop tasks and they gave subjective ratings of their mental fatigue on the Visual Analogue Scale (VAS) prior to taking either of the Stroop tasks. In Study 1, participants showed a ceiling effect on the Stroop accuracy measure, there was strong concurrent validity for the Stroop with significant score differences between the Stroop's congruent and incongruent conditions (p < .001), and there was excellent response time reliability (ICC = 0.926) on day two when participants took the Stroop twice within a 30-minute inter-test interval. However, there were significant test-retest performance differences with respect to cognitive inhibition (p < .001). In Study 2, mental fatigue from the Flanker/Reverse Flanker test resulted in a significantly worse second Stroop performance (p = .045). We concluded that the Stroop task demonstrated strong concurrent validity and response time reliability among older adults, but it showed sensitivity to mental fatigue, and repeated administrations within the short 30-minute test-retest interval revealed that the most important Stroop measure (cognitive inhibition) was unreliable. We discuss the implications of these findings.

Delineating cognitive resilience using fractal regulation: Cross-sectional and longitudinal evidence from the Rush Memory and Aging Project

INTRODUCTION

Degradation of fractal patterns in actigraphy independently predicts dementia risk. Such observations motivated the study to understand the role of fractal regulation in the context of neuropathologies.

METHODS

We examined associations of fractal regulation with neuropathologies and longitudinal cognitive changes in 533 older participants who were followed annually with actigraphy and cognitive assessments until death with brain autopsy performed. Two measures for fractal patterns were extracted from actigraphy, namely, α1 (representing the fractal regulation at time scales of <90 min) and α2 (for time scales 2 to 10 h).

RESULTS

We found that larger α1 was associated with lower burdens of Lewy body disease or cerebrovascular disease pathologies; both α1 and α2 were associated with cognitive decline. They explained an additional significant portion of the variance in the rate of cognitive decline above and beyond neuropathologies.

DISCUSSION

Fractal patterns may be used as a biomarker for cognitive resilience against dementia-related neuropathologies.

Genetic and Clinical Correlates of AI-Based Brain Aging Patterns in Cognitively Unimpaired Individuals

Importance

Brain aging elicits complex neuroanatomical changes influenced by multiple age-related pathologies. Understanding the heterogeneity of structural brain changes in aging may provide insights into preclinical stages of neurodegenerative diseases.

Objective

To derive subgroups with common patterns of variation in participants without diagnosed cognitive impairment (WODCI) in a data-driven manner and relate them to genetics, biomedical measures, and cognitive decline trajectories.

Design, Setting, and Participants

Data acquisition for this cohort study was performed from 1999 to 2020. Data consolidation and harmonization were conducted from July 2017 to July 2021. Age-specific subgroups of structural brain measures were modeled in 4 decade-long intervals spanning ages 45 to 85 years using a deep learning, semisupervised clustering method leveraging generative adversarial networks. Data were analyzed from July 2021 to February 2023 and were drawn from the Imaging-Based Coordinate System for Aging and Neurodegenerative Diseases (iSTAGING) international consortium. Individuals WODCI at baseline spanning ages 45 to 85 years were included, with greater than 50 000 data time points.

Exposures

Individuals WODCI at baseline scan.

Main Outcomes and Measures

Three subgroups, consistent across decades, were identified within the WODCI population. Associations with genetics, cardiovascular risk factors (CVRFs), amyloid β (Aβ), and future cognitive decline were assessed.

Results

In a sample of 27 402 individuals (mean [SD] age, 63.0 [8.3] years; 15 146 female [55%]) WODCI, 3 subgroups were identified in contrast with the reference group: a typical aging subgroup, A1, with a specific pattern of modest atrophy and white matter hyperintensity (WMH) load, and 2 accelerated aging subgroups, A2 and A3, with characteristics that were more distinct at age 65 years and older. A2 was associated with hypertension, WMH, and vascular disease-related genetic variants and was enriched for Aβ positivity (ages ≥65 years) and apolipoprotein E (APOE) ε4 carriers. A3 showed severe, widespread atrophy, moderate presence of CVRFs, and greater cognitive decline. Genetic variants associated with A1 were protective for WMH (rs7209235: mean [SD] B = -0.07 [0.01]; P value = 2.31 × 10-9) and Alzheimer disease (rs72932727: mean [SD] B = 0.1 [0.02]; P value = 6.49 × 10-9), whereas the converse was observed for A2 (rs7209235: mean [SD] B = 0.1 [0.01]; P value = 1.73 × 10-15 and rs72932727: mean [SD] B = -0.09 [0.02]; P value = 4.05 × 10-7, respectively); variants in A3 were associated with regional atrophy (rs167684: mean [SD] B = 0.08 [0.01]; P value = 7.22 × 10-12) and white matter integrity measures (rs1636250: mean [SD] B = 0.06 [0.01]; P value = 4.90 × 10-7).

Conclusions and Relevance

The 3 subgroups showed distinct associations with CVRFs, genetics, and subsequent cognitive decline. These subgroups likely reflect multiple underlying neuropathologic processes and affect susceptibility to Alzheimer disease, paving pathways toward patient stratification at early asymptomatic stages and promoting precision medicine in clinical trials and health care.

Cognitive resilience/reserve: Myth or reality? A review of definitions and measurement methods

INTRODUCTION

This review examines the concept of cognitive reserve (CR) in relation to brain aging, particularly in the context of dementia and its early stages. CR refers to an individual's ability to maintain or regain cognitive function despite brain aging, damage, or disease. Various factors, including education, occupation complexity, leisure activities, and genetics are believed to influence CR.

METHODS

We revised the literature in the context of CR. A total of 842 articles were identified, then we rigorously assessed the relevance of articles based on titles and abstracts, employing a systematic approach to eliminate studies that did not align with our research objectives.

RESULTS

We evaluate-also in a critical way-the methods commonly used to define and measure CR, including sociobehavioral proxies, neuroimaging, and electrophysiological and genetic measures. The challenges and limitations of these measures are discussed, emphasizing the need for more targeted research to improve the understanding, definition, and measurement of CR.

CONCLUSIONS

The review underscores the significance of comprehending CR in the context of both normal and pathological brain aging and emphasizes the importance of further research to identify and enhance this protective factor for cognitive preservation in both healthy and neurologically impaired older individuals.

HIGHLIGHTS

This review examines the concept of cognitive reserve in brain aging, in the context of dementia and its early stages. We have evaluated the methods commonly used to define and measure cognitive reserve. Sociobehavioral proxies, neuroimaging, and electrophysiological and genetic measures are discussed. The review emphasizes the importance of further research to identify and enhance this protective factor for cognitive preservation.

Risk factors associated with cognitive performance and cognitive impairment in older adults with type 1 diabetes: Data from the Wireless Innovation for Seniors with Diabetes Mellitus (WISDM) study

BACKGROUND

Adults with type 1 diabetes (T1D) are considered at increased risk for cognitive impairment and accelerated brain aging. However, longitudinal data on cognitive impairment and dementia in this population are scarce.

OBJECTIVE

To identify risk factors associated with cognitive performance and cognitive impairment in a longitudinal sample of older adults with T1D.

METHODS

We analyzed data collected as part of the Wireless Innovation for Seniors with Diabetes Mellitus (WISDM) Study, in which 22 endocrinology practices participated. Randomized participants with T1D ≥60 years of age who completed at least one cognitive assessment were included in this study (n = 203). Cognitive impairment was classified using published recommendations.

RESULTS

Older age, male sex, non-private health insurance, worse daily functioning, diagnosis of neuropathy, and longer duration of diabetes were associated with worse cognitive performance, but not cognitive impairment. 49 % and 39 % of the sample met criteria for cognitive impairment at baseline and 52 weeks respectively. Of the participants that had data at both time points, 10 % were normal at baseline and impaired at 52 weeks and 22 % of participants (44 % of those classified with cognitive impairment at baseline) reverted to normal over 52 weeks.

CONCLUSION

This study indicated that several demographic and clinical characteristics are associated with worse cognitive performance in older adults with T1D, but there were no associations between these characteristics and cognitive impairment defined by NIH Toolbox cognitive impairment criteria. Caution is warranted when assessing cognition in older adults with T1D, as a large percentage of those identified as having cognitive impairment at baseline reverted to normal after 52 weeks. There is need for future studies on the interrelationship of cognition and aging to better understand the effects of T1D on cognitive health, to improve clinical monitoring and help mitigate the risk of dementia in this population.

Genetic deletion of hormone-sensitive lipase in mice reduces cerebral blood flow but does not aggravate the impact of diet-induced obesity on memory

Hormone-sensitive lipase (HSL) is active throughout the brain and its genetic ablation impacts brain function. Its activity in the brain was proposed to regulate bioactive lipid availability, namely eicosanoids that are inflammatory mediators and regulate cerebral blood flow (CBF). We aimed at testing whether HSL deletion increases susceptibility to neuroinflammation and impaired brain perfusion upon diet-induced obesity. HSL-/-, HSL+/-, and HSL+/+ mice of either sex were fed high-fat diet (HFD) or control diet for 8 weeks, and then assessed in behavior tests (object recognition, open field, and elevated plus maze), metabolic tests (insulin and glucose tolerance tests and indirect calorimetry in metabolic cages), and CBF determination by arterial spin labeling (ASL) magnetic resonance imaging (MRI). Immunofluorescence microscopy was used to determine coverage of blood vessels, and morphology of astrocytes and microglia in brain slices. HSL deletion reduced CBF, most prominently in cortex and hippocampus, while HFD feeding only lowered CBF in the hippocampus of wild-type mice. CBF was positively correlated with lectin-stained vessel density. HSL deletion did not exacerbate HFD-induced microgliosis in the hippocampus and hypothalamus. HSL-/- mice showed preserved memory performance when compared to wild-type mice, and HSL deletion did not significantly aggravate HFD-induced memory impairment in object recognition tests. In contrast, HSL deletion conferred protection against HFD-induced obesity, glucose intolerance, and insulin resistance. Altogether, this study points to distinct roles of HSL in periphery and brain during diet-induced obesity. While HSL-/- mice were protected against metabolic syndrome development, HSL deletion reduced brain perfusion without leading to aggravated HFD-induced neuroinflammation and memory dysfunction.

Long-term findings on working memory neural dynamics in healthcare workers after mild COVID-19

OBJECTIVE

Understanding the long-term impact of Coronavirus Disease 2019 (COVID-19) on cognitive function, even in mild cases, is critical to the well-being of individuals, especially for healthcare workers who are at increased risk of exposure to the virus. To the best of our knowledge, the electrophysiological activity underlying cognitive functioning has not yet been explored.

METHODS

Seventy-seven healthcare workers took part in the study (43 with mild infection about one year before the study and 34 uninfected). To assess cognitive status, event-related potentials (ERPs) and behavioural responses were recorded while participants performed a working memory task.

RESULTS

COVID-19 participants exhibited a distinct neural pattern with lower parieto-occipital N1 amplitudes and higher frontal P2 amplitudes as compared to non-infected healthcare workers. We found no behavioural differences (reaction times and error rates) in working memory functioning between groups.

CONCLUSIONS

This neural pattern suggests the presence of a decrement of processing resources linked to the encoding of sensory information (N1), followed by the enhanced of the P2 response which could be interpreted as the activation of compensation mechanism in COVID-19 participants.

SIGNIFICANCE

The current findings point out that ERPs could serve as valuable neural indices for detecting distinctive patterns in working memory functioning of COVID-19 participants, even in mild cases. However, further research is required to precisely ascertain the long-term cognitive effects of COVID-19 beyond one-year post-infection.

Occupational differences in a Dutch sample of patients with primary progressive aphasia, behavioral variant frontotemporal dementia, and Alzheimer's dementia

BACKGROUND

Cognitive reserve is a potential mechanism to cope with brain damage as a result of dementia, which can be defined by indirect proxies, including education level, leisure time activities, and occupational attainment. In this study we explored the association between dementia diagnosis and type of occupation in a retrospective Dutch outpatient memory clinic sample of patients with primary progressive aphasia (PPA), behavioral variant frontotemporal dementia (bvFTD), and Alzheimer's Dementia (AD).

METHODS

We included data from 427 patients (bvFTD n = 87, PPA n = 148, AD n = 192) and compared the frequency of occupations (11 categories) between patients and data from the Dutch census using Pearson Χ2 tests and we calculated odds ratios (OR) by means of multinomial logistic regression analyses. We also investigated patient group differences in age, sex, education, disease duration, and global cognition.

RESULTS

The frequency of teachers in patients with PPA was significantly higher than the frequency of teachers in patients with bvFTD [OR = 4.79, p = .007] and AD [OR = 2.04, p = .041]. The frequency of teachers in patients with PPA (16%) was also significantly higher than the frequency of teachers in the Dutch census [5.3%; OR = 3.27, p < .001]. The frequency of teachers in both bvFTD and AD groups were not significantly different from the frequency of teachers in the Dutch census (p = .078 and p = .513, respectively).

CONCLUSIONS

A potential explanation for our results is the so called "wear and tear" hypothesis, suggesting that teachers have a communication-wise demanding occupation - and therefore are at higher risk to develop PPA. Alternatively, teaching requires continuous communication, hence teachers are more sensitive to subtle changes in their speech and language abilities. Our findings broaden our understanding of the relationship between occupational activity and cognitive reserve in the development of dementia.

Biophysical models applied to dementia patients reveal links between geographical origin, gender, disease duration, and loss of neural inhibition

BACKGROUND

The hypothesis of decreased neural inhibition in dementia has been sparsely studied in functional magnetic resonance imaging (fMRI) data across patients with different dementia subtypes, and the role of social and demographic heterogeneities on this hypothesis remains to be addressed.

METHODS

We inferred regional inhibition by fitting a biophysical whole-brain model (dynamic mean field model with realistic inter-areal connectivity) to fMRI data from 414 participants, including patients with Alzheimer's disease, behavioral variant frontotemporal dementia, and controls. We then investigated the effect of disease condition, and demographic and clinical variables on the local inhibitory feedback, a variable related to the maintenance of balanced neural excitation/inhibition.

RESULTS

Decreased local inhibitory feedback was inferred from the biophysical modeling results in dementia patients, specific to brain areas presenting neurodegeneration. This loss of local inhibition correlated positively with years with disease, and showed differences regarding the gender and geographical origin of the patients. The model correctly reproduced known disease-related changes in functional connectivity.

CONCLUSIONS

Results suggest a critical link between abnormal neural and circuit-level excitability levels, the loss of grey matter observed in dementia, and the reorganization of functional connectivity, while highlighting the sensitivity of the underlying biophysical mechanism to demographic and clinical heterogeneities in the patient population.

The association between cannabis use and neuroimaging measures in older adults: findings from the UK biobank

BACKGROUND

Cannabis use has increased in recent years. However, the long-term implications of cannabis use on brain health remain unknown. We explored the associations of cannabis use with volumetric brain magnetic resonance imaging (MRI) measures in dementia-free older adults.

METHODS

This cross-sectional and longitudinal study included dementia-free participants of the UK Biobank aged ≥60 years. Linear regression models were used to evaluate the association of cannabis use and patterns of use with volumetric brain MRI measures. The association between cannabis use and change in brain MRI measures over time was also tested. All models were adjusted for potential confounders.

RESULTS

The sample included 19,932 participants (mean age 68 ± 5 years, 48% men), 3,800 (19%) reported lifetime use of cannabis. Cannabis use was associated with smaller total, white, grey and peripheral cortical grey matter volumes (B = -6,690 ± 1,157; P < 0.001, B = -4,396 ± 766; P < 0.001, B = -2,140 ± 690; P = 0.002 and B = -2,451 ± 606; P < 0.001, respectively). Among cannabis users, longer duration of use was associated with smaller total brain, grey and cortical grey matter volumes (B = -7,878 ± 2,396; P = 0.001, B = -5,411 ± 1,430; P < 0.001, B = -5,396 ± 1,254; P < 0.001, respectively), and with increased white matter hyperintensity volume (B = 0.09 ± 0.03; P = 0.008). Additionally, current vs. former users (B = -10,432 ± 4,395; P = 0.020) and frequent versus non-frequent users (B = -2,274 ± 1,125; P = 0.043) had smaller grey and cortical grey matter volumes, respectively. No significant associations were observed between cannabis use and change in brain MRI measures.

DISCUSSION

Our findings suggest that cannabis use, particularly longer duration and frequent use, may be related to smaller grey and white matter volumes in older ages, but not to late-life changes in these measures over time.

Long-term olfactory enrichment promotes non-olfactory cognition, noradrenergic plasticity and remodeling of brain functional connectivity in older mice

Brain functional and structural changes lead to cognitive decline during aging, but a high level of cognitive stimulation during life can improve cognitive performances in the older adults, forming the cognitive reserve. Noradrenaline has been proposed as a molecular link between environmental stimulation and constitution of the cognitive reserve. Taking advantage of the ability of olfactory stimulation to activate noradrenergic neurons of the locus coeruleus, we used repeated olfactory enrichment sessions over the mouse lifespan to enable the cognitive reserve buildup. Mice submitted to olfactory enrichment, whether started in early or late adulthood, displayed improved olfactory discrimination at late ages and interestingly, improved spatial memory and cognitive flexibility. Moreover, olfactory and non-olfactory cognitive performances correlated with increased noradrenergic innervation in the olfactory bulb and dorsal hippocampus. Finally, c-Fos mapping and connectivity analysis revealed task-specific remodeling of functional neural networks in enriched older mice. Long-term olfactory enrichment thus triggers structural noradrenergic plasticity and network remodeling associated with better cognitive aging and thereby forms a promising mouse model of the cognitive reserve buildup.

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.

Scanning ultrasound-mediated memory and functional improvements do not require amyloid-β reduction

A prevalent view in treating age-dependent disorders including Alzheimer's disease (AD) is that the underlying amyloid plaque pathology must be targeted for cognitive improvements. In contrast, we report here that repeated scanning ultrasound (SUS) treatment at 1 MHz frequency can ameliorate memory deficits in the APP23 mouse model of AD without reducing amyloid-β (Aβ) burden. Different from previous studies that had shown Aβ clearance as a consequence of blood-brain barrier (BBB) opening, here, the BBB was not opened as no microbubbles were used. Quantitative SWATH proteomics and functional magnetic resonance imaging revealed that ultrasound induced long-lasting functional changes that correlate with the improvement in memory. Intriguingly, the treatment was more effective at a higher frequency (1 MHz) than at a frequency within the range currently explored in clinical trials in AD patients (286 kHz). Together, our data suggest frequency-dependent bio-effects of ultrasound and a dissociation of cognitive improvement and Aβ clearance, with important implications for the design of trials for AD therapies.

Considering the response in addition to the challenge - a narrative review in appraisal of a motor reserve framework

The remarkable increase in human life expectancy over the past century has been achieved at the expense of the risk of age-related impairment and disease. Neurodegeneration, be it part of normal aging or due to neurodegenerative disorders, is characterized by loss of specific neuronal populations, leading to increasing clinical impairment. The individual course may be described as balance between aging- or disease-related pathology and intrinsic mechanisms of adaptation. There is plenty of evidence that the human brain is provided with exhaustible resources to maintain function in the face of adverse conditions. While a reserve concept has mainly been coined in cognitive neuroscience, emerging evidence suggests similar mechanisms to underlie individual differences of adaptive capacity within the motor system. In this narrative review, we summarize what has been proposed to date about a motor reserve (mR) framework. We present current evidence from research in aging subjects and people with neurological conditions, followed by a description of what is known about potential neuronal substrates of mR so far. As there is no gold standard of mR quantification, we outline current approaches which describe various indicators of mR. We conclude by sketching out potential future directions of research. Expediting our understanding of differences in individual motor resilience towards aging and disease will eventually contribute to new, individually tailored therapeutic strategies. Provided early diagnosis, enhancing the individual mR may be suited to postpone disease onset by years and may be an efficacious contribution towards healthy aging, with an increased quality of life for the elderly.

Neural attentional filters and behavioural outcome follow independent individual trajectories over the adult lifespan

Preserved communication abilities promote healthy ageing. To this end, the age-typical loss of sensory acuity might in part be compensated for by an individual's preserved attentional neural filtering. Is such a compensatory brain-behaviour link longitudinally stable? Can it predict individual change in listening behaviour? We here show that individual listening behaviour and neural filtering ability follow largely independent developmental trajectories modelling electroencephalographic and behavioural data of N = 105 ageing individuals (39-82 y). First, despite the expected decline in hearing-threshold-derived sensory acuity, listening-task performance proved stable over 2 y. Second, neural filtering and behaviour were correlated only within each separate measurement timepoint (T1, T2). Longitudinally, however, our results raise caution on attention-guided neural filtering metrics as predictors of individual trajectories in listening behaviour: neither neural filtering at T1 nor its 2-year change could predict individual 2-year behavioural change, under a combination of modelling strategies.

Occupational complexity of paid work and housework, and its impact on the cognitive performance in community dwelling older adults, preliminary results

Work and activity could be an important source of cognitive enrichment. Activities that are more challenging concerning the cognitive functions that are put into practice are associated with lower risk of cognitive decline in old age.

Objective

The present study aimed to assess the impact of occupational complexity and household tasks in three cognitive domains (verbal episodic memory, language, and executive functions) in older adults residing within the community.

Methods

A trail analysis was executed, using the structural equations procedure in 120 participants assessed with main lifetime occupational activity and household tasks questionnaire, as well as a neuropsychological assessment battery for memory, language, and executive functions.

Results

The regression weights analysis indicated that complexity in household chores showed moderate effects on executive functions (β=0.19; p=0.027) and that occupational complexity of paid work showed effects on memory (β=0.26; p=0.008), language (β=0.38; p<0.001), and executive functions (β=0.55; p<0.001).

Conclusion

Paid work promotes cognitive reserve, contrary to household activities which seem to have a moderate impact on cognition. Differences in activity complexity not only impact people´s economic and social status and possibilities but can also determine different courses of aging and cognitive risk.

Subtypes of brain change in aging and their associations with cognition and Alzheimer's disease biomarkers

Structural brain changes underly cognitive changes in older age and contribute to inter-individual variability in cognition. Here, we assessed how changes in cortical thickness, surface area, and subcortical volume, are related to cognitive change in cognitively unimpaired older adults using structural magnetic resonance imaging (MRI) data-driven clustering. Specifically, we tested (1) which brain structural changes over time predict cognitive change in older age (2) whether these are associated with core cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarkers phosphorylated tau (p-tau) and amyloid-β (Aβ42), and (3) the degree of overlap between clusters derived from different structural features. In total 1899 cognitively healthy older adults (50 - 93 years) were followed up to 16 years with neuropsychological and structural MRI assessments, a subsample of which (n = 612) had CSF p-tau and Aβ42 measurements. We applied Monte-Carlo Reference-based Consensus clustering to identify subgroups of older adults based on structural brain change patterns over time. Four clusters for each brain feature were identified, representing the degree of longitudinal brain decline. Each brain feature provided a unique contribution to brain aging as clusters were largely independent across modalities. Cognitive change and baseline cognition were best predicted by cortical area change, whereas higher levels of p-tau and Aβ42 were associated with changes in subcortical volume. These results provide insights into the link between changes in brain morphology and cognition, which may translate to a better understanding of different aging trajectories.

Estimation of cognitive reserve and its impact on cognitive performance in older adults

OBJECTIVES

Cognitive reserve provides evidence in the search for answers regarding the role that lifestyle has in the protection of cognition in old age. Through a structural equations model, different things were analyzed: the relative weight of education, occupational complexity, free time activities and the intelligence quotient in cognitive reserve; and its impact on three cognitive domains: memory, language and executive functions.

DESIGN

A trail analysis was executed, using structural equations procedure.

PARTICIPANTS

167 older participants (mean = 76.74 years, standard deviation = 6.8 years).

MEASUREMENTS

Participants were assessed with: Sociodemographic Questionnaire, Occupational Activity Agency Questionnaire, Social Participation Questionnaire and Neuropsychological Evaluation Battery for: memory, language and executive functions.

RESULTS

The cognitive reserve factor is well represented by the measures included, with values ​​between .43 and .86, and shows a direct effect on language (β = .52, p < .001), executive functions (β = .77, p <.001), and memory (β = .36, p = .003).

CONCLUSIONS

In conclusion, lifestyle factors, such as education, occupational complexity, leisure time activities and intelligence quotient have an impact on the conformation of cognitive reserve and performance in some psychological processes.

Biopsychosocial contexts influence adult cognitive function concurrently and longitudinally

Background

Cognitive aging is a complex process that impacts human behavior. Identifying the factors that preserve cognitive functioning is a public health priority, given that 20% of the US population will be at least 65 years old in the next decade. Biopsychosocial determinants of cognitive decline across the lifespan are often examined as ecological factors that independently moderate cognitive aging, despite the known complexity surrounding these relationships.

Objective

We aimed to address this gap by exploring the synergistic and simultaneous relationship between risk and protective factors on cognitive functioning.

Method

Using the MIDUS study datasets, we examined the relationships among physiological markers, friendship quality, and global cognition functioning, concurrently and longitudinally over ten years. Our participants included 929 healthy (417 men, 512 women) adults (average age at Time 1: 54.6 ± 11.6 years). Exploratory analyses examining the effects of racial minority status were also conducted.

Results

Cross-sectionally, age, and friendship quality moderated the relationship between vagally-mediated heart rate variability (vm-HRV) and cognition such that younger adults with greater friendship quality had a negative relationship between vm-HRV and cognitive performance; our unexpected finding suggests the heart-brain relationship is sensitive to the biopsychosocial environment. Longitudinally, higher IL-6 levels at Time 1 predicted poorer cognitive performance a decade later, but only among those with greater levels of friendship quality, especially for white-identifying individuals.

Conclusions

The relationships among physiological risk factors, social protective factors and cognitive functioning appear to be temporally different during mid-adulthood. Given many of the whole sample findings were not replicated within the racial minority subgroup, we suggest that these relationships should be examined in a larger and more diverse racial minority sample to determine whether this study lacked the power necessary to detect a relationship or if the relationships are in fact different by racial minority sub-group. In addition, future research should overcome the study's reliance on healthy adults and self-report measures of friendship quality by including adults with pre-existing cognitive impairments, and employing more real-time measures of friendship quality, such as daily diary or ecological momentary assessment.

Personality predictors of dementia diagnosis and neuropathological burden: An individual participant data meta-analysis

INTRODUCTION

The extent to which the Big Five personality traits and subjective well-being (SWB) are discriminatory predictors of clinical manifestation of dementia versus dementia-related neuropathology is unclear.

METHODS

Using data from eight independent studies (Ntotal = 44,531; Ndementia = 1703; baseline Mage = 49 to 81 years, 26 to 61% female; Mfollow-up range = 3.53 to 21.00 years), Bayesian multilevel models tested whether personality traits and SWB differentially predicted neuropsychological and neuropathological characteristics of dementia.

RESULTS

Synthesized and individual study results indicate that high neuroticism and negative affect and low conscientiousness, extraversion, and positive affect were associated with increased risk of long-term dementia diagnosis. There were no consistent associations with neuropathology.

DISCUSSION

This multistudy project provides robust, conceptually replicated and extended evidence that psychosocial factors are strong predictors of dementia diagnosis but not consistently associated with neuropathology at autopsy.

HIGHLIGHTS

N(+), C(-), E(-), PA(-), and NA(+) were associated with incident diagnosis. Results were consistent despite self-report versus clinical diagnosis of dementia. Psychological factors were not associated with neuropathology at autopsy. Individuals with higher conscientiousness and no diagnosis had less neuropathology. High C individuals may withstand neuropathology for longer before death.

Clinical severity in Parkinson's disease is determined by decline in cortical compensation

Dopaminergic dysfunction in the basal ganglia, particularly in the posterior putamen, is often viewed as the primary pathological mechanism behind motor slowing (i.e. bradykinesia) in Parkinson's disease. However, striatal dopamine loss fails to account for interindividual differences in motor phenotype and rate of decline, implying that the expression of motor symptoms depends on additional mechanisms, some of which may be compensatory in nature. Building on observations of increased motor-related activity in the parieto-premotor cortex of Parkinson patients, we tested the hypothesis that interindividual differences in clinical severity are determined by compensatory cortical mechanisms and not just by basal ganglia dysfunction. Using functional MRI, we measured variability in motor- and selection-related brain activity during a visuomotor task in 353 patients with Parkinson's disease (≤5 years disease duration) and 60 healthy controls. In this task, we manipulated action selection demand by varying the number of possible actions that individuals could choose from. Clinical variability was characterized in two ways. First, patients were categorized into three previously validated, discrete clinical subtypes that are hypothesized to reflect distinct routes of α-synuclein propagation: diffuse-malignant (n = 42), intermediate (n = 128) or mild motor-predominant (n = 150). Second, we used the scores of bradykinesia severity and cognitive performance across the entire sample as continuous measures. Patients showed motor slowing (longer response times) and reduced motor-related activity in the basal ganglia compared with controls. However, basal ganglia activity did not differ between clinical subtypes and was not associated with clinical scores. This indicates a limited role for striatal dysfunction in shaping interindividual differences in clinical severity. Consistent with our hypothesis, we observed enhanced action selection-related activity in the parieto-premotor cortex of patients with a mild-motor predominant subtype, both compared to patients with a diffuse-malignant subtype and controls. Furthermore, increased parieto-premotor activity was related to lower bradykinesia severity and better cognitive performance, which points to a compensatory role. We conclude that parieto-premotor compensation, rather than basal ganglia dysfunction, shapes interindividual variability in symptom severity in Parkinson's disease. Future interventions may focus on maintaining and enhancing compensatory cortical mechanisms, rather than only attempting to normalize basal ganglia dysfunction.

Dementia care and prevention in community settings: a built environment framework for cognitive health promotion

PURPOSE OF REVIEW

Most people with dementia live in the community. As lifespan increases, one in three persons aged 85+ are expected to live with dementia. We conduct a systematic search to identify frameworks for dementia care and prevention in community settings. This is important to ensure quality of life for people living with cognitive decline (PLCD).

RECENT FINDINGS

61 frameworks are synthesized into the dementia care and prevention in community (DCPC) framework. It highlights three levels of provision: built environment and policy supports, access and innovation, and inclusion across stages of decline. Domains of intervention include: basic needs; built environment health and accessibility; service access and use; community health infrastructure; community engagement; mental health and wellbeing; technology; end-of-life care; cultural considerations; policy, education, and resources. Personhood is not adequately represented in current built environment frameworks. This is supplemented with 14 articles on lived experiences at home and social practices that contribute to PLCD's social identity and psychological safety.

SUMMARY

Policy makers, health and built environment professionals must work together to promote "personhood in community" with PLCD. Clinicians and community staff may focus on inclusion, social identity and a sense of at-homeness as attainable outcomes despite diagnosis.

Brain gray matter morphometry relates to onset age of bilingualism and theory of mind in young and older adults

Lifelong bilingualism may result in neural reserve against decline not only in the general cognitive domain, but also in social cognitive functioning. In this study, we show the brain structural correlates that are associated with second language age of acquisition (L2AoA) and theory of mind (the ability to reason about mental states) in normal aging. Participants were bilingual adults (46 young, 50 older) who completed a theory-of-mind task battery, a language background questionnaire, and an anatomical MRI scan to obtain cortical morphometric features (i.e., gray matter volume, thickness, and surface area). Findings indicated a theory-of-mind decline in older adults compared to young adults, controlling for education and general cognition. Importantly, earlier L2AoA and better theory-of-mind performance were associated with larger volume, higher thickness, and larger surface area in the bilateral temporal, medial temporal, superior parietal, and prefrontal brain regions. These regions are likely to be involved in mental representations, language, and cognitive control. The morphometric association with L2AoA in young and older adults were comparable, but its association with theory of mind was stronger in older adults than young adults. The results demonstrate that early bilingual acquisition may provide protective benefits to intact theory-of-mind abilities against normal age-related declines.

Cognitive reserve and the risk of postoperative neurocognitive disorders in older age

Background

Postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) are postoperative neurocognitive disorders (PNDs) that frequently occur in the aftermath of a surgical intervention. Cognitive reserve (CR) is a concept posited to explain why cognitive health varies between individuals. On this qualitative understanding of cognitive health, factors like IQ, education level, and occupational complexity can affect the impact of neuropathological processes on cognitive outcomes.

Methods

We investigated the association between CR and POD and CR and POCD on data from 713 patients aged≥65 years with elective surgery. Peak pre-morbid IQ was estimated from vocabulary. Occupational complexity was coded according to the Dictionary of Occupational Titles (DOT). Education level was classed according to the International Standard Classification of Education (ISCED). These three factors were used as proxies of CR. In a series of regression models, age, sex, depression, site of surgery, and several lifestyle and vascular factors were controlled for.

Results

Patients with a higher IQ had lower odds of developing POD. We found no significant association between the other two CR markers with POD. None of the CR markers was associated with POCD.

Conclusion

The significant association of a higher IQ with lower POD risk allows for the stratification of elderly surgical patients by risk. This knowledge can aid the prevention and/or early detection of POD. Further research should attempt to determine the lack of associations of CR markers with POCD in our study.

Unexpected cognitive similarities between older adults and young people: Scores variability and cognitive performances

BACKGROUND

Increased interindividual variability in cognitive performance during aging has been proposed as an indicator of cognitive reserve.

OBJECTIVE

To determine if interindividual variability performance in episodic memory (PAL), working memory (SWM), reaction time (RTI), and sustained attention (RVP) could differentiate clusters of differential cognitive performance in healthy young and older adults and search for cognitive tests that most contribute to these differential performances.

METHODS

We employed hierarchical cluster and canonical discriminant function analyses of cognitive scores using the Cambridge Neuropsychological Test Automated Battery (CANTAB) to identify cognitive variability in older and young adults using the coefficient of variability of cognitive performances between and within groups. We also analyzed potential influences of age, education, and physical activity.

RESULTS

Cluster analysis distinguished groups with differential cognitive performance and correlation analysis revealed coefficient of variability and cognitive performance associations. The greater the coefficient of variability the poorer was cognitive performance in RTI but not in PAL and SWM. Older adults showed diverse trajectories of cognitive decline, and better education or higher percentage of physically active individuals exhibited better cognitive performance in both older and young adults.

CONCLUSION

PAL and SWM are the most sensitive tests to investigate the wide age range encompassing older and young adults. In older adults' intragroup analysis PAL showed greater discriminatory capacity, indicating its potential for clinical applications late in life. Our data underscore the importance of studying variability as a tool for early detection of subtle cognitive declines and for interpreting results that deviate from normality.

Neuropsychological insights into exercise addiction: the role of brain structure and self-efficacy in middle-older individuals

This study aimed to investigate the relationship between exercise addiction and brain structure in middle-older individuals, and to examine the role of self-efficacy in mediating physiological changes associated with exercise addiction. A total of 133 patients exhibiting symptoms of exercise addiction were recruited for this study (male = 43, age 52.86 ± 11.78 years). Structural magnetic resonance imaging and behavioral assessments were administered to assess the study population. Voxel-based morphological analysis was conducted using SPM12 software. Mediation analysis was employed to explore the potential neuropsychological mechanism of self-efficacy in relation to exercise addiction. The findings revealed a positive correlation between exercise addiction and gray matter volume in the right inferior temporal region and the right hippocampus. Conversely, there was a negative correlation with gray matter volume in the left Rolandic operculum. Self-efficacy was found to indirectly influence exercise addiction by affecting right inferior temporal region gray matter volume and acted as a mediating variable in the relationship between the gray matter volume of right inferior temporal region and exercise addiction. In summary, this study elucidates the link between exercise addiction and brain structure among middle-older individuals. It uncovers the intricate interplay among exercise addiction, brain structure, and psychological factors. These findings enhance our comprehension of exercise addiction and offer valuable insights for the development of interventions and treatments.

Elucidating Multimodal Imaging Patterns in Accelerated Brain Aging: Heterogeneity through a Discriminant Analysis Approach Using the UK Biobank Dataset

Accelerated brain aging (ABA) intricately links with age-associated neurodegenerative and neuropsychiatric diseases, emphasizing the critical need for a nuanced exploration of heterogeneous ABA patterns. This investigation leveraged data from the UK Biobank (UKB) for a comprehensive analysis, utilizing structural magnetic resonance imaging (sMRI), diffusion magnetic resonance imaging (dMRI), and resting-state functional magnetic resonance imaging (rsfMRI) from 31,621 participants. Pre-processing employed tools from the FMRIB Software Library (FSL, version 5.0.10), FreeSurfer, DTIFIT, and MELODIC, seamlessly integrated into the UKB imaging processing pipeline. The Lasso algorithm was employed for brain-age prediction, utilizing derived phenotypes obtained from brain imaging data. Subpopulations of accelerated brain aging (ABA) and resilient brain aging (RBA) were delineated based on the error between actual age and predicted brain age. The ABA subgroup comprised 1949 subjects (experimental group), while the RBA subgroup comprised 3203 subjects (control group). Semi-supervised heterogeneity through discriminant analysis (HYDRA) refined and characterized the ABA subgroups based on distinctive neuroimaging features. HYDRA systematically stratified ABA subjects into three subtypes: SubGroup 2 exhibited extensive gray-matter atrophy, distinctive white-matter patterns, and unique connectivity features, displaying lower cognitive performance; SubGroup 3 demonstrated minimal atrophy, superior cognitive performance, and higher physical activity; and SubGroup 1 occupied an intermediate position. This investigation underscores pronounced structural and functional heterogeneity in ABA, revealing three subtypes and paving the way for personalized neuroprotective treatments for age-related neurological, neuropsychiatric, and neurodegenerative diseases.

Cognitive alterations and brain functional changes following chemotherapy treatment in breast cancer patients: A systematic review on resting-state fMRI studies

Cognitive dysfunctions and functional brain modifications are among the side effects reported by breast cancer patients that persist beyond the chemotherapy. This paper aims at synthesizing the evidence on cognitive and functional brain changes and their associations in breast cancer patients treated with chemotherapy. A systematic literature search was performed using PubMed, Ovid MEDLINE, Scopus, and Embase up to July 2022. Eligible studies evaluated adult women with breast cancer treated with systemic chemotherapy, that performed cognitive assessment and resting-state functional MRI. Methodological quality was assessed. Sixteen studies were included, with a total of 1054 female participants. All studies reported alterations mainly concerned the fronto-parieto-temporal system and specifically involved the disruption of the DMN. Consistent with these findings, BCPs showed changes in cognitive performance reporting dysfunctions in executive ability, memory, and attention. However, not all the studies found a significant association between functional brain alterations and cognitive dysfunction. Some limitations including lack of sample homogeneity and different methodological approaches were reported. This work highlighted the presence of cognitive dysfunctions and functional brain alteration in breast cancer patients treated with chemotherapy. This allows a greater awareness of the side effects, promoting better clinical management. However, further research is needed to investigate the cause-effect relationship between cognitive and functional alterations.

From theory to practice: translating the concept of cognitive resilience to novel therapeutic targets that maintain cognition in aging adults

While the concept of cognitive resilience is well-established it has not been defined in a way that can be measured. This has been an impediment to studying its underlying biology and to developing instruments for its clinical assessment. This perspective highlights recent work that has quantified the expression of cortical proteins associated with cognitive resilience, thus facilitating studies of its complex underlying biology and the full range of its clinical effects in aging adults. These initial studies provide empirical support for the conceptualization of resilience as a continuum. Like other conventional risk factors, some individuals manifest higher-than-average cognitive resilience and other individuals manifest lower-than-average cognitive resilience. These novel approaches for advancing studies of cognitive resilience can be generalized to other aging phenotypes and can set the stage for the development of clinical tools that might have the potential to measure other mechanisms of resilience in aging adults. These advances also have the potential to catalyze a complementary therapeutic approach that focuses on augmenting resilience via lifestyle changes or therapies targeting its underlying molecular mechanisms to maintain cognition and brain health even in the presence of untreatable stressors like brain pathologies that accumulate in aging adults.

The Effect of COVID-19 on Middle-Aged Adults' Mental Health: A Mixed-Method Case-Control Study on the Moderating Effect of Cognitive Reserve

The COVID-19 pandemic has increased the vulnerability of adults to mental health effects, and the study of protective factors has become crucial. Cognitive reserve (CR) is a well-known protective factor against cognitive decline and several health factors; however, its protective effect on mental health during the pandemic has been rarely addressed. Thus, this study explored, through a mixed-method design, the effect of CR on perceived distress and PTSD-like symptoms in middle-aged participants who have survived severe COVID-19 and a matched control group. A total of 432 participants filled out self-report measures of CR, PTSD, depression, and anxiety, and were also asked to provide narration about their COVID-19-related experience. COVID-19 significantly affected the chances of reporting different mental health symptoms; levels of CR played a protective role in reducing their severity. Moreover, adults with higher CR seemed to be more realistic, focusing less on positive emotions, and elaborating more on the sense of anxiety when describing their experience: this might be an indication of a lower use of suppression to regulate emotions. Practical implications of these findings and future directions have been also discussed.

Mini-ACE: Validation Study Among Older People in Long-Term Care

Background

The Mini-Addenbrooke's Cognitive Examination (M-ACE) is a valid and reliable tool that accurately differentiates various types of cognitive impairment from Normal-cognition assessed in multiple settings. However, its validity among older individuals in long-term care (LTC) was not yet established. Therefore, we sought to assess the Portuguese M-ACE's validity, reliability, and accuracy in detecting cognitive impairment no-dementia (CIND) in LTC users.

Methods

A comprehensive assessment was performed on 196 LTC Portuguese users aged ≥ 60 years, among whom 71 had Normal-cognition, and 125 had CIND.

Results

The M-ACE was found to be reliable (McDonald's ω = .86, Cronbach's α = .85) and consistent over time (r = .72; ICC = .83) and between raters (k = .92). Strong correlations with related measures supported construct validity (both r = .67). The M-ACE accurately distinguished CIND from Normal-cognition with a cut-off of 17 points (AUC = 0.81, Sensitivity = 81.7%, Specificity = 74.4%).

Conclusion

Our findings suggest that the Portuguese M-ACE is a valid and reliable cognitive assessment tool for LTC users, allowing for accurate differentiation between CIND and Normal-cognition. Thus, the M-ACE's use could contribute to the early detection and intervention of cognitive disorders, especially among older adults in LTC.

African Ancestry Individuals with Higher Educational Attainment Are Resilient to Alzheimer's Disease Measured by pTau181

Background

Cognitive and functional abilities in individuals with Alzheimer's disease (AD) pathology (ADP) are highly variable. Factors contributing to this variability are not well understood. Previous research indicates that higher educational attainment (EA) correlates with reduced cognitive impairments among those with ADP. While cognitive and functional impairments are correlated, they are distinguishable in their manifestations.

Objective

To investigate whether levels of education are associated with functional impairments among those with ADP.

Methods

This research involved 410 African American (AA) individuals (Institutional Review Boards 20070307, 01/27/2023) to ascertain whether EA correlates with functional resilience and if this effect varies between APOE ɛ4 carriers and non-carriers. Utilizing EA as a cognitive reserve proxy, CDR-FUNC as a functional difficulties measure, and blood pTau181 as an ADP proxy, the non-parametric Mann-Whitney U test assessed the relationship between EA and CDR-FUNC in individuals with advanced pTau181 levels.

Results

The results showed that EA correlated with functional difficulties in AA individuals with high levels of pTau181, such that individuals with high EA are more likely to have better functional ability compared to those with lower EA (W = 730.5, p = 0.0007). Additionally, we found that the effect of high EA on functional resilience was stronger in ɛ4 non-carriers compared to ɛ4 carriers (W = 555.5, p = 0.022).

Conclusion

This study extends the role of cognitive reserve and EA to functional performance showing that cognitive reserve influences the association between ADP burden and functional difficulties. Interestingly, this protective effect seems less pronounced in carriers of the strong genetic risk allele ɛ4.

Effect of Late-Stage Meniere's Disease and Vestibular Functional Impairment on Hippocampal Atrophy

OBJECTIVE

We investigated correlations among clinical features, degree of inner ear endolymphatic hydrops (EH), and hippocampal volume (HV) in different stages of Meniere's disease (MD).

METHODS

From February 2021 to April 2022, clinical data were collected from 99 patients (39 males, 60 females, mean age: 50.4 ± 10.0 [range: 26-69] years) with unilateral MD admitted to the Department of Vertigo Disease of Shandong ENT Hospital. The left and right ears were affected in 64 and 35 patients, respectively. There were 50 and 49 cases in early (Stages 1, 2) and late stages (Stages 3, 4), respectively. Fifty healthy participants were included as controls. Audiovestibular function test results, EH grading using gadolinium-enhanced magnetic resonance imaging (MRI), and HV determined on MRI were analyzed for patients at different stages of MD.

RESULTS

Between-group comparisons of early and late MD revealed significant differences in the disease course, vestibular function (VF), degree of EH, and HV. There were no significant between-group differences based on age, sex, affected side, subjective degree of dizziness, hospital anxiety, or depression. Mean HV in patients with early-stage MD was correlated with the canal paresis value of the caloric test and pure tone hearing threshold, HV in late-stage patients was correlated with vestibular EH.

CONCLUSION

Patients with late-stage MD exhibited severe auditory and VF impairments, increased EH, and atrophy of the HV. More advanced disease was associated with greater vestibular damage and degree of EH.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:410-418, 2024.

Measures of cognitive reserve: An umbrella review

Objective: Recently, there has been a growing interest in operationalizing and measuring cognitive reserve (CR) for clinical and research purposes. This umbrella review aims to summarize the existing systematic and meta-analytic reviews about measures of CR. Method: A literature search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the guidelines of Aromataris et al. (2015) to identify the systematic reviews and meta-analysis involving the assessment of CR. The methodological quality of the papers included in this umbrella review was assessed with A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR-2) and Specialist Unit for Review Evidence (SURE). Results: Thirty-one reviews were identified, sixteen of which were systematic reviews, and fifteen were meta-analyses. Most of the reviews had a critically low quality, according to AMSTAR-2. The reviews included between two and 135 studies. Most of the papers focused on older adults, mainly those with dementia. CR was measured using one to six proxies, but most considered each proxy separately. The most assessed proxies of CR were education on its own, combined with occupation and/or engagement in activities or combined with parental education, bilingualism, and engagement in activities when four CR proxies were studied. Most of the studies included in higher quality reviews focused on three proxies, with education and engagement in activities being the most evaluated using CR questionnaires. Conclusion: Despite the growing interest in measuring CR, its operationalization did not improve since the last umbrella review in this field.

Land/Water Aerobic Activities: Two Sides of the Same Coin. A Comparative Analysis on the Effects in Cognition of Alzheimer's Disease

 Evidence in the literature indicates that aerobic physical activity may have a protective role in aging pathologies. However, it has not been clarified whether different types of aerobic exercise produce different effects. In particular, these potential differences have not been explored in patients with Alzheimer's disease (AD). The present narrative review has the specific aim of evaluating whether land (walking/running) and water (swimming) aerobic activities exert different effects on cognitive functions and neural correlates in AD patients. In particular, the investigation is carried out by comparing the evidence provided from studies on AD animal models and on patients. On the whole, we ascertained that both human and animal studies documented beneficial effects of land and water aerobic exercise on cognition in AD. Also, the modulation of numerous biological processes is documented in association with structural modifications. Remarkably, we found that aerobic activity appears to improve cognition per se, independently from the specific kind of exercise performed. Aerobic exercise promotes brain functioning through the secretion of molecular factors from skeletal muscles and liver. These molecular factors stimulate neuroplasticity, reduce neuroinflammation, and inhibit neurodegenerative processes leading to amyloid-β accumulation. Additionally, aerobic exercise improves mitochondrial activity, reducing oxidative stress and enhancing ATP production. Aerobic activities protect against AD, but implementing exercise protocols for patients is challenging. We suggest that health policies and specialized institutions should direct increasing attention on aerobic activity as lifestyle modifiable factor for successful aging and age-related conditions.

Development of Efficient Brain Age Estimation Method Based on Regional Brain Volume From Structural Magnetic Resonance Imaging

OBJECTIVE

We aimed to create an efficient and valid predicting model which can estimate individuals' brain age by quantifying their regional brain volumes.

METHODS

A total of 2,560 structural brain magnetic resonance imaging (MRI) scans, along with demographic and clinical data, were obtained. Pretrained deep-learning models were employed to automatically segment the MRI data, which enabled fast calculation of regional brain volumes. Brain age gaps for each subject were estimated using volumetric values from predefined 12 regions of interest (ROIs): bilateral frontal, parietal, occipital, and temporal lobes, as well as bilateral hippocampus and lateral ventricles. A larger weight was given to the ROIs having a larger mean volumetric difference between the cognitively unimpaired (CU) and cognitively impaired group including mild cognitive impairment (MCI), and dementia groups. The brain age was predicted by adding or subtracting the brain age gap to the chronological age according to the presence or absence of the atrophy region.

RESULTS

The study showed significant differences in brain age gaps among CU, MCI, and dementia groups. Furthermore, the brain age gaps exhibited significant correlations with education level and measures of cognitive function, including the clinical dementia rating sum-of-boxes and the Korean version of the Mini-Mental State Examination.

CONCLUSION

The brain age that we developed enabled fast and efficient brain age calculations, and it also reflected individual's cognitive function and cognitive reserve. Thus, our study suggested that the brain age might be an important marker of brain health that can be used effectively in real clinical settings.

Associations between white matter hyperintensities, lacunes, entorhinal cortex thickness, declarative memory and leisure activity in cognitively healthy older adults: A 7-year study

INTRODUCTION

Cerebral small vessel disease (cSVD) is a growing epidemic that affects brain health and cognition. Therefore, a more profound understanding of the interplay between cSVD, brain atrophy, and cognition in healthy aging is of great importance. In this study, we examined the association between white matter hyperintensities (WMH) volume, number of lacunes, entorhinal cortex (EC) thickness, and declarative memory in cognitively healthy older adults over a seven-year period, controlling for possible confounding factors. Because there is no cure for cSVD to date, the neuroprotective potential of an active lifestyle has been suggested. Supporting evidence, however, is scarce. Therefore, a second objective of this study is to examine the relationship between leisure activities, cSVD, EC thickness, and declarative memory.

METHODS

We used a longitudinal dataset, which consisted of five measurement time points of structural MRI and psychometric cognitive ability and survey data, collected from a sample of healthy older adults (baseline N = 231, age range: 64-87 years, age M = 70.8 years), to investigate associations between cSVD MRI markers, EC thickness and verbal and figural memory performance. Further, we computed physical, social, and cognitive leisure activity scores from survey-based assessments and examined their associations with brain structure and declarative memory. To provide more accurate estimates of the trajectories and cross-domain correlations, we applied latent growth curve models controlling for potential confounders.

RESULTS

Less age-related thinning of the right (β = 0.92, p<.05) and left EC (β = 0.82, p<.05) was related to less declarative memory decline; and a thicker EC at baseline predicted less declarative memory loss (β = 0.54, p<.05). Higher baseline levels of physical (β = 0.24, p<.05), and social leisure activity (β = 0.27, p<.01) predicted less thinning of right EC. No relation was found between WMH or lacunes and declarative memory or between leisure activity and declarative memory. Higher education was initially related to more physical activity (β = 0.16, p<.05) and better declarative memory (β = 0.23, p<.001), which, however, declined steeper in participants with higher education (β = -.35, p<.05). Obese participants were less physically (β = -.18, p<.01) and socially active (β = -.13, p<.05) and had thinner left EC (β = -.14, p<.05) at baseline. Antihypertensive medication use (β = -.26, p<.05), and light-to-moderate alcohol consumption (β = -.40, p<.001) were associated with a smaller increase in the number of lacunes whereas a larger increase in the number of lacunes was observed in current smokers (β = 0.30, p<.05).

CONCLUSIONS

Our results suggest complex relationships between cSVD MRI markers (total WMH, number of lacunes, right and left EC thickness), declarative memory, and confounding factors such as antihypertensive medication, obesity, and leisure activitiy. Thus, leisure activities and having good cognitive reserve counteracting this neurodegeneration. Several confounding factors seem to contribute to the extent or progression/decline of cSVD, which needs further investigation in the future. Since there is still no cure for cSVD, modifiable confounding factors should be studied more intensively in the future to maintain or promote brain health and thus cognitive abilities in older adults.

The Association between Education and Cognitive Performance Varies at Different Levels of Cognitive Performance: A Quantile Regression Approach

INTRODUCTION

Educational differences in cognitive performance among older adults are well documented. Studies that explore this association typically estimate a single average effect of education on cognitive performance. We argue that the processes that contribute to the association between education and cognitive performance are unlikely to have equal effects at all levels of cognitive performance. In this study, we employ an analytical approach that enables us to go beyond averages to examine the association between education and five measures of global and domain-specific cognitive performance across the outcome distributions.

METHODS

This cross-sectional study included 1,780 older adults aged 58-68 years from the Longitudinal Aging Study Amsterdam. Conditional quantile regression was used to examine variation across the outcome distribution. Cognitive outcomes included Mini-Mental State Examination (MMSE) score, crystallized intelligence, information processing speed, episodic memory, and a composite score of global cognitive performance.

RESULTS

The results showed that the associations between education and different cognitive measures varied across the outcome distributions. Specifically, we found that education had a stronger association with crystallized intelligence, MMSE, and a composite cognitive performance measure in the lower tail of performance distributions. The associations between education and information processing speed and episodic memory were uniform across the outcome distributions.

CONCLUSION

Larger associations between education and some domains of cognitive performance in the lower tail of the performance distributions imply that inequalities are primarily generated among individuals with lower performance rather than among average and high performers. Additionally, the varying associations across some of the outcome distributions indicate that estimating a single average effect through standard regression methods may overlook variations in cognitive performance between educational groups. Future studies should consider heterogeneity across the outcome distribution.

Risk Polymorphisms of FNDC5, BDNF, and NTRK2 and Poor Education Interact and Aggravate Age-Related Cognitive Decline

Cognitive abilities tend to decline with aging, with variation between individuals, and many studies seek to identify genetic biomarkers that more accurately anticipate risks related to pathological aging. We investigated the influence of BDNF, NTRK2, and FNDC5 single nucleotide polymorphisms (SNPs) on the cognitive performance of young and older adults with contrasting educational backgrounds. We addressed three questions: (1) Is education associated with reduced age-related cognitive decline? (2) Does the presence of SNPs explain the variation in cognitive performance observed late in life? (3) Is education differentially associated with cognition based on the presence of BDNF, NTRK2, or FNDC5 polymorphisms? We measured the cognitive functions of young and older participants, with lower and higher education, using specific and sensitive tests of the Cambridge Automated Neuropsychological Test Assessment Battery. A three-way ANOVA revealed that SNPs were associated with differential performances in executive functions, episodic memory, sustained attention, mental and motor response speed, and visual recognition memory and that higher educational levels improved the affected cognitive functions. The results revealed that distinct SNPs affect cognition late in life differentially, suggesting their utility as potential biomarkers and emphasizing the importance of cognitive stimulation that advanced education early in life provides.

Cumulative Stress Exposure and Cognitive Function Among Older Adults: The Moderating Role of a Healthy Lifestyle

OBJECTIVES

Although chronic stress is a risk factor for poor age-related cognitive health, there is limited research that has examined how cumulative stress across the lifespan affects cognitive aging. There may also be resilience factors that minimize the effects of cumulative stress on cognitive health. Engaging in a healthy lifestyle is protective against cognitive decline and may therefore interact with cumulative stress to buffer the stress-cognition relationship. The objective of the current study was to examine the moderating role of a healthy lifestyle, comprised of physical activity, social engagement, and sleep quality, in the relationship between cumulative stress exposure (CSE) and baseline and change in cognitive performance (global cognition, episodic memory, executive function) over 9 years among 1,297 older adults in the Midlife in the United States cohort (Mage = 69.0 ± 6.4, 57.8% female).

METHODS

CSE and healthy lifestyle behaviors were indexed using self-reported questionnaires at baseline, and cognitive function was assessed using a battery of standardized neuropsychological tests at baseline and follow-up.

RESULTS

Controlling for age, sex, education, race, marital status, employment status, hypertension, diabetes, and depression, higher CSE was associated with poorer baseline performance and slower decline over time in global cognition and executive function, but not episodic memory. A healthy lifestyle did not significantly moderate the relationship between cumulative stress and cognitive function. Exploratory analyses showed a significant cumulative stress-cognition relationship among females only.

DISCUSSION

This study lends support for a lifespan model of cognitive aging and suggests that the cognitive health consequences of stress extend beyond immediate timescales.

Brain and cognitive reserve mitigate balance dysfunction in multiple sclerosis

BACKGROUND

Approximately two-thirds of patients with multiple sclerosis (MS) complain different degrees of balance dysfunction, but some of them are able to withstand considerable disease burden without an overt balance impairment. Here, we tested the hypothesis that brain and cognitive reserve lessen the effect of MS-related tissue damage on balance control.

METHODS

We measured the postural sway of 148 patients and 74 sex- and age-matched healthy controls by force platform under different conditions reflecting diverse neuro-pathological substrates of balance dysfunction: eyes opened (EO), eyes closed (EC), and while performing the Stroop test, i.e., dual-task (DT). Lesion volumes on T2-hyperintense and T1-hypointense sequences, and normalized brain volume provided estimations of MS-related tissue damage in patients with MS. Hierarchical linear regressions explored the protective effect against the MS-related tissue damage of intracranial volume and educational attainment (proxies for brain and cognitive reserve, respectively) on balance.

RESULTS

Larger intracranial volume and high educational attainment mitigated the detrimental effect of MS-related tissue damage on postural sway under EO (adjusted-R2=0.20 and 0.27, respectively, p<0.01) and DT (adjusted-R2=0.22 and 0.30, respectively, p<0.06) conditions. Neither educational level nor brain size was associated with postural sway under EC condition.

CONCLUSION

Our findings suggest a protective role of brain and cognitive reserve even on balance, an outcome that relies on both motor control and higher order processing resources. The lack of a protective effect on postural sway under EC condition confirms that this latter outcome is closer associated with spinal cord rather than brain damage.

Enhanced Dynamic Laterality Based on Functional Subnetworks in Patients with Bipolar Disorder

An ocean of studies have pointed to abnormal brain laterality changes in patients with bipolar disorder (BD). Determining the altered brain lateralization will help us to explore the pathogenesis of BD. Our study will fill the gap in the study of the dynamic changes of brain laterality in BD patients and thus provide new insights into BD research. In this work, we used fMRI data from 48 BD patients and 48 normal controls (NC). We constructed the dynamic laterality time series by extracting the dynamic laterality index (DLI) at each sliding window. We then used k-means clustering to partition the laterality states and the Arenas-Fernandez-Gomez (AFG) community detection algorithm to determine the number of states. We characterized subjects' laterality characteristics using the mean laterality index (MLI) and laterality fluctuation (LF). Compared with NC, in all windows and state 1, BD patients showed higher MLI in the attention network (AN) of the right hemisphere, and AN in the left hemisphere showed more frequent laterality fluctuations. AN in the left hemisphere of BD patients showed higher MLI in all windows and state 3 compared to NC. In addition, in the AN of the right hemisphere in state 1, higher MLI in BD patients was significantly associated with patient symptoms. Our study provides new insights into the understanding of BD neuropathology in terms of brain dynamic laterality.