Cognitive reserve, cognition, and real-world functioning in MCI: A systematic review and meta-analysis

The protective role of cognitive reserve: an empirical study in mild cognitive impairment

BACKGROUND

Mild cognitive impairment (MCI) describes an aging profile characterized by a cognitive decline that is worse than expected in normal aging but less pervasive and critical than full-blown dementia. In the absence of an effective treatment strategy, it is important to identify factors that can protect against progression to dementia. In this field, it is hypothesized that one aspect that may be a protective factor against the neurotypical outcome of dementia is cognitive reserve (CR). Cognitive reserve is the ability to maintain cognitive functionality despite accumulating brain pathology.

OBJECTIVES

The present study aimed to identify and analyze the differences in CR between healthy adults and patients with MCI. Specifically, it is hypothesized that (i) healthy older adult people have higher CR than older adult people diagnosed with MCI, and (II) CR could predict the classification of subjects into people with or without MCI.

METHODS

Two hundred forty-three adults (mean age = 60.4, SD = 7.4) participated in the present study and were classified into three groups based on Petersen's MCI criteria: healthy controls (HC), amnestic MCI (aMCI), and non-amnestic MCI (naMCI). The Cognitive Reserve Index questionnaire (CRIq) was administered to assess the level of CR, FINDINGS: Results showed that HC had significantly higher CR scores than participants diagnosed with aMCI and naMCI. Moreover, a binomial logistic regression suggested that low CR was a significant risk factor for the MCI diagnosis.

CONCLUSIONS

The clinical picture that emerged from the results showed that lower CR could be considered a characteristic of pathological aging, such as MCI.Public significance statement, Since the brain attempts to cope with life-related changes or pathologies, it is fundamental for both clinicians and researchers to investigate further the factors that contribute to brain resilience. As an indirect expression of brain reserve, cognitive reserve may be both a marker and a predictor of adaptive aging.

Definition and analysis of gray matter atrophy subtypes in mild cognitive impairment based on data-driven methods

Introduction

Mild cognitive impairment (MCI) is an important stage in Alzheimer's disease (AD) research, focusing on early pathogenic factors and mechanisms. Examining MCI patient subtypes and identifying their cognitive and neuropathological patterns as the disease progresses can enhance our understanding of the heterogeneous disease progression in the early stages of AD. However, few studies have thoroughly analyzed the subtypes of MCI, such as the cortical atrophy, and disease development characteristics of each subtype.

Methods

In this study, 396 individuals with MCI, 228 cognitive normal (CN) participants, and 192 AD patients were selected from ADNI database, and a semi-supervised mixture expert algorithm (MOE) with multiple classification boundaries was constructed to define AD subtypes. Moreover, the subtypes of MCI were obtained by using the multivariate linear boundary mapping of support vector machine (SVM). Then, the gray matter atrophy regions and severity of each MCI subtype were analyzed and the features of each subtype in demography, pathology, cognition, and disease progression were explored combining the longitudinal data collected for 2 years and analyzed important factors that cause conversion of MCI were analyzed.

Results

Three MCI subtypes were defined by MOE algorithm, and the three subtypes exhibited their own features in cortical atrophy. Nearly one-third of patients diagnosed with MCI have almost no significant difference in cerebral cortex from the normal aging population, and their conversion rate to AD are the lowest. The subtype characterized by severe atrophy in temporal lobe and frontal lobe have a faster decline rate in many cognitive manifestations than the subtype featured with diffuse atrophy in the whole cortex. APOE ε4 is an important factor that cause the conversion of MCI to AD.

Conclusion

It was proved through the data-driven method that MCI collected by ADNI baseline presented different subtype features. The characteristics and disease development trajectories among subtypes can help to improve the prediction of clinical progress in the future and also provide necessary clues to solve the classification accuracy of MCI.

Sleep-wake behavior, perceived fatigability, and cognitive reserve in older adults

INTRODUCTION

The effects of sleep-wake behavior on perceived fatigability and cognitive abilities when performing daily activities have not been investigated across levels of cognitive reserve (CR).

METHODS

CR Index Questionnaire (CRIq) data were collected and subjected to moderated mediation analysis.

RESULTS

In amnestic mild cognitive impairment (aMCI; n = 41), CR moderated sleep-related impairments (SRIs), and fatigability at low CR (CRIq < 105.8, p = 0.004) and mean CR (CRIq = 126.9, p = 0.03) but not high CR (CRIq > 145.9, p = 0.65) levels. SRI affected cognitive abilities mediated by fatigability at low CR (p < 0.001) and mean CR (p = 0.003) levels. In healthy controls (n = 13), SRI in fatigability did not alter cognitive abilities across CR levels; controls had higher leisure scores than patients with aMCI (p = 0.003, effect size = 0.93).

DISCUSSION

SRI can amplify impaired cognitive abilities through exacerbation of fatigability in patients with aMCI with below-mean CR. Therefore, improving sleep-wake regulation and leisure activities may protect against fatigability and cognitive decline.

HIGHLIGHTS

Clinical fatigue and fatigability cannot be alleviated by rest. Clinical fatigability disrupts daily activities during preclinical Alzheimer's. High cognitive reserve mitigates sleep-wake disturbance effects. High cognitive reserve attenuates clinical fatigability effects on daily functioning. Untreated obstructive sleep apnea potentiates Alzheimer's pathology in the brain.

Moderating effect of education on glymphatic function and cognitive performance in mild cognitive impairment

Objective

This research aims to investigate putative mechanisms between glymphatic activity and cognition in mild cognitive impairment (MCI) and analyzes whether the relationship between cognitive reserve (CR) and cognition was mediated by glymphatic activity.

Methods

54 MCI patients and 31 NCs were enrolled to evaluate the bilateral diffusivity along the perivascular spaces and to acquire an index for diffusivity along the perivascular space (ALPS-index) on diffusion tensor imaging (DTI). The year of education was used as a proxy for CR. The ALPS-index was compared between two groups and correlation analyses among the ALPS-index, cognitive function, and CR were conducted. Mediation analyses were applied to investigate the correlations among CR, glymphatic activity and cognition.

Results

MCI group had a significantly lower right ALPS-index and whole brain ALPS-index, but higher bilateral diffusivity along the y-axis in projection fiber area (Dyproj) than NCs. In MCI group, the left Dyproj was negatively related to cognitive test scores and CR, the whole brain ALPS-index was positively correlated with cognitive test scores and CR. Mediation analysis demonstrated that glymphatic activity partially mediated the correlations between CR and cognitive function.

Conclusion

MCI exhibited decreased glymphatic activity compared to NCs. CR has a protective effect against cognitive decline in MCI, and this effect may be partially mediated by changes in glymphatic activity.

Correlations between cognitive reserve, gray matter, and cerebrospinal fluid volume in healthy elders and mild cognitive impairment patients

Objective

To explore the effect of cognitive reserve (CR) on brain volume and cerebrospinal fluid (CSF) in patients with mild cognitive impairment (MCI) and healthy elders (HE).

Methods

31 HE and 50 MCI patients were collected in this study to obtain structural MRI, cognitive function, and composite CR scores. Educational attainment, leisure time, and working activity ratings from two groups were used to generate cognitive reserve index questionnaire (CRIq) scores. The different volumes of brain regions and CSF were obtained using uAI research portal in both groups, which were taken as the regions of interest (ROI), the correlation analysis between ROIs and CRIq scores were conducted.

Results

The scores of CRIq, CRIq-leisure time, and CRIq-education in HE group were significantly higher than patients in MCI group, and the montreal cognitive assessment (MoCA) and minimum mental state examination (MMSE) scores were positively correlated with the CRIq, CRIq-education in both groups, and were positively correlated with CRIq-leisure time in MCI group. The scores of auditory verbal learning test (AVLT) and verbal fluency test (VFT) were also positively correlated with CRIq, CRIq-leisure time, and CRIq-education in MCI group, but the score of AVLT was only positively correlated with CRIq in HE group. Moreover, in MCI group, the volume of the right middle cingulate cortex and the right parahippocampal gyrus were negatively correlated with the CRIq, and the volume of CSF, peripheral CSF, and third ventricle were positively correlated with the CRIq-leisure time score. The result of mediation analysis suggested that right parahippocampal gryus mediated the main effect of the relationship between CRIq and MoCA score in MCI group.

Conclusion

People with higher CR show better levels of cognitive function, and MCI patients with higher CR showed more severe volume atrophy of the right middle cingulate cortex and the right parahippocampal gyrus, but more CSF at a given level of global cognition.

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.

s-CRIq: the online short version of the Cognitive Reserve Index Questionnaire

BACKGROUND

The wide use of the term Cognitive Reserve (CR) is in need of a clear and shared definition of its concept and of the development of new tools, quick and easy to use and updated for the people of today. This study describes the online short CRIq (s-CRIq), the new shorter version of the CRIq, following an item analysis revision, and compares the data distribution of different samples.

METHODS

The s-CRIq was administered online to 435 people while another 440 filled out the s-CRIq in self-administration. A further 588 participants had been administered the original paper-and-pencil long CRIq and 344 the online long CRIq.

RESULTS

The major difference in the databases of s-CRIq versus the long versions is an increased score in education and in leisure activity. However, the density distributions of the total score of CRI in the 4 databases share 64% of their areas, and at least two of them share 84%.

CONCLUSION

The s-CRIq proved to be a simple and easy-to-administer tool. Similarly, to the original version, the s-CRIq is freely available on the web, and it is our hope that it will be of fruitful use for researchers and clinicians alike.

Network of mental activities, cognitive function and depression in older men and women

BACKGROUND

Evidence suggests that lifestyle activities impact cognitive and mental health in older populations. However, how lifestyle factors are associated with one another, and which factors are most important for cognitive function and mental health has received comparatively little attention.

DESIGN

Bayesian-Gaussian network analysis was used to investigate unique associations between mental activities (MA; i.e., activities involving cognitive engagement), global cognition, and depression at three time-points in a large sample of older adults (baseline, 2 years, and 4 years follow-up).

SETTING

This study used longitudinal data from participants living in Australia and participating in the Sydney Memory and Ageing Study.

PARTICIPANTS

The sample included 998 participants (55% female) aged between 70 and 90, without a diagnosis of dementia at baseline.

MEASUREMENTS

Neuropsychological assessment of global cognition, self-reported depressive symptoms, and self-reported information about daily MA.

RESULTS

Cognitive functioning was positively associated with playing tabletop games and using the internet in both sexes at all time-points. MA were differentially linked in men and women. Depression was not consistently associated with MA in men across the three time-points; women who visited artistic events consistently had lower depression scores.

CONCLUSIONS

Engaging with tabletop games and using the internet was associated with better cognition in both sexes, however sex acted as a modifier for other associations. These findings are useful for future investigations that consider interactive associations between MA, cognition, and mental health in older adults, and their possible roles in promoting healthy aging.

The Protective Role of Cognitive Reserve in Mild Cognitive Impairment: A Systematic Review

Cognitive reserve (CR) represents the ability to optimize performance and functioning to cope with brain damage or disease. CR reflects the capability to adaptively and flexibly use cognitive processes and brain networks to compensate for the deterioration typical of aging. Several studies have investigated the potential role of CR in aging, especially from the perspective of preventing and protecting against dementia and Mild Cognitive Impairment (MCI). This systematic literature review aimed to investigate the role of CR as a protective factor against MCI and associated cognitive decline. The review process was conducted according to the PRISMA statement. For this purpose, ten studies were analyzed. The results of this review show that high CR is significantly associated with a reduced risk of MCI. In addition, a significant positive relationship between CR and cognitive functioning is observed when comparing subjects with MCI and healthy subjects and within people with MCI. Thus, the results confirm the positive role of cognitive reserve in mitigating cognitive impairment. The evidence from this systematic review is consistent with the theoretical models of CR. Indeed, previous research hypothesized that specific individual experiences (such as leisure activities) allow a person to acquire successful neural resources over the years to cope with cognitive decline.

The Differential Effect of Schooling and Physical Activity on Dementia in Older Women and Men from Brazil: Implications for Policymaking

Background: Modifiable risk factors exert crucial impact on dementia. Objective: We sought to answer the question: do two modifiable risk factors, schooling level and physical activity (PA), affect cognitive function similarly in each sex? Methods: This cross-sectional study was conducted in 2019 and 2021, and the survey was applied to the residents of the metropolitan area of Santos, a seashore of Sao Paulo State. Four hundred and twenty-two participants (women = 254 and men = 168) were eligible. Baecke questionnaire for the elderly was applied for the classification as physically inactive (PI) or active (PA). Cognitive function was assessed by the Mini-Mental State Examination (MMSE) and the Clinical Dementia Rating (CDR). Participants were also stratified by schooling status for both sexes. Results: Higher education had a sex-independent positive influence on MMSE and CDR (p <  0.001). PA influences positively MMSE in older women (PI: 25±5 and PA: 27±3, p <  0.03), but has no effect in older men (26±5 and 25±5, p >  0.05). Concordantly, older women who were PA (1.7 and 0 %) showed a lower prevalence of dementia compared with PI (6.2 and 2.1%), for mild and moderate respectively. Active older women had higher odds of improving the MMSE score (OR: 1.093; 95% CI: 1.008–1.186) than men (OR: 0.97 (95% CI: 0.896–1.051). Conclusion: Education affects cognitive function equally in Brazilian elderly whereas older women are more responsive to the beneficial effects of PA for dementia than men.

Acupuncture Treatment Modulate Regional Homogeneity of Dorsal Lateral Prefrontal Cortex in Patients with Amnesic Mild Cognitive Impairment

Background: Although acupuncture is widely used to improve cognitive and memory in the amnesic mild cognitive impairment (aMCI) patients with impressive effectiveness, its neural mechanism remains largely unclear. Objective: We aimed to explore functional magnetic resonance imaging (fMRI) mechanism of acupuncture for aMCI. Methods: A randomized, controlled, single-blind research was performed. A total of 46 aMCI patients were randomly assigned into verum and sham acupuncture group, who received a total of 24 times treatments (3 times/week, 8 weeks). Clinical evaluation and fMRI scanning were performed at baseline and after treatment for all aMCI patients. The interaction effects and inter-group effects of regional homogeneity (ReHo) were performed using mixed effect models, and the correlations between clinical improvement and neuroimaging changes before and after verum acupuncture treatment were analyzed using Pearson correlations. Results: As a result, interaction effects showed increased ReHo value in left dorsal lateral prefrontal cortex (DLPFC), increased functional connectivity between left DLPFC and left precuneus, and decreased functional connectivity between left DLPFC and left inferior temporal gyrus after verum acupuncture but inversely after sham acupuncture in the aMCI. Condition effects showed increased ReHo in right lingual gyrus, and bilateral post-central gyrus after verum and sham acupuncture in the aMCI. In addition, the changed Montreal Cognitive Assessment scores in verum acupuncture group were significantly correlated with changed ReHo values in left DLPFC. Conclusion: Together, our findings further confirmed that acupuncture could be used as a promising complementary therapy for aMCI by modulating function of left DLPFC to improve cognitive symptoms.