The effects of intelligence and education on the development of dementia. A test of the brain reserve hypothesis

Sex differences in the progression to Alzheimer's disease: a combination of functional and structural markers

Mild cognitive impairment (MCI) has been frequently interpreted as a transitional phase between healthy cognitive aging and dementia, particularly of the Alzheimer's disease (AD) type. Of note, few studies explored that transition from a multifactorial perspective, taking into consideration the effect of basic factors such as biological sex. In the present study 96 subjects with MCI (37 males and 59 females) were followed-up and divided into two subgroups according to their clinical outcome: "progressive" MCI (pMCI = 41), if they fulfilled the diagnostic criteria for AD at the end of follow-up; and "stable" MCI (sMCI = 55), if they remained with the initial diagnosis. Different markers were combined to characterize sex differences between groups, including magnetoencephalography recordings, cognitive performance, and brain volumes derived from magnetic resonance imaging. Results indicated that the pMCI group exhibited higher low-frequency activity, lower scores in neuropsychological tests and reduced brain volumes than the sMCI group, being these measures significantly correlated. When sex was considered, results revealed that this pattern was mainly due to the influence of the females' sample. Overall, females exhibited lower cognitive scores and reduced brain volumes. More interestingly, females in the pMCI group showed an increased theta activity that correlated with a more abrupt reduction of cognitive and volumetric scores as compared with females in the sMCI group and with males in the pMCI group. These findings suggest that females' brains might be more vulnerable to the effects of AD pathology, since regardless of age, they showed signs of more pronounced deterioration than males.

ENHANCE: a comparative prospective longitudinal study of cognitive outcomes after 3 years of hearing aid use in older adults

Background

With an aging population, the prevalence of hearing loss and dementia are increasing rapidly. Hearing loss is currently considered the largest potentially modifiable risk factor for dementia. The effect of hearing interventions on cognitive function should therefore be investigated, as if effective, these may be successfully implemented to modify cognitive outcomes for older adults with hearing loss.

Methods

This prospective longitudinal observational cohort study compared outcomes of a convenience sample of prospectively recruited first-time hearing aid users without dementia from an audiology center with those of community-living older adults participating in a large prospective longitudinal cohort study with/without hearing loss and/or hearing aids. All participants were assessed at baseline, 18 months, and 36 months using the same measures.

Results

Participants were 160 audiology clinic patients (48.8% female patient; mean age 73.5 years) with mild-severe hearing loss, fitted with hearing aids at baseline, and 102 participants of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Aging (AIBL) (55.9% female patient; mean age 74.5 years). 18- and 36-month outcomes of subsets of the first participants to reach these points and complete the cognition assessment to date are compared. Primary comparative analysis showed cognitive stability for the hearing aid group while the AIBL group declined on working memory, visual attention, and psychomotor function. There was a non-significant trend for decline in visual learning for the AIBL group versus no decline for the hearing aid group. The hearing aid group showed significant decline on only 1 subtest and at a significantly slower rate than for the AIBL participants (p < 0.05). When education effects on cognitive trajectory were controlled, the HA group still performed significantly better on visual attention and psychomotor function (lower educated participants only) compared to the AIBL group but not on working memory or visual learning. Physical activity had no effect on cognitive performance trajectory.

Conclusion

Hearing aid users demonstrated significantly better cognitive performance to 3 years post-fitting, suggesting that hearing intervention may delay cognitive decline/dementia onset in older adults. Further studies using appropriate measures of cognition, hearing, and device use, with longer follow-up, are required.

The Role of Incarceration as a Risk Factor for Cognitive Impairment

OBJECTIVES

The objective of this study was to understand disparities in cognitive impairment between middle-aged formerly incarcerated (FI) and nonincarcerated individuals.

METHODS

The 1979 National Longitudinal Survey of Youth is a nationally representative longitudinal data set containing information on incarceration, cognitive functioning, and other health conditions. Using a modified version of the Telephone Interview for Cognitive Status (TICS-m), adapted from the Health and Retirement Study, we analyzed the association between incarceration and cognitive impairment, cognitive impairment-not dementia and dementia. Multivariable regression models were estimated, including prior incarceration status and covariates associated with incarceration and cognitive functioning.

RESULTS

FI individuals had lower unadjusted scores on TICS-m (-2.5, p < .001) and had significantly greater unadjusted odds ratios (OR) for scoring in the cognitive impairment (OR = 2.4, p < .001) and dementia (OR = 2.7, p < .001) range. Differences were largely explained by a combination of risk factors associated with incarceration and cognition. Education and premorbid cognition (measured by Armed Forces Qualification Test) separately and completely explained differences in the odds of dementia. Regardless of incarceration status, Blacks and Hispanics had significantly greater odds of cognitive impairment and dementia relative to Whites, holding other factors constant.

DISCUSSION

The association between prior incarceration and cognitive impairment in middle age was largely explained by differences in educational attainment and premorbid cognitive functioning, supporting the cognitive reserve hypothesis. Greater prevalence of cognitive impairment and dementia among the FI could create challenges and should be considered in reentry planning. Structural and institutional factors should be considered when addressing health disparities in Alzheimer's Disease and Related Dementias.

The effect of memory cue duration on performance in the directed forgetting task in healthy aging

Although forgetting is usually considered a memory error, intentional forgetting can function as an adaptive mechanism. The current study examined the effect of increased processing time on directed forgetting in aging as a mechanism to compensate for age-related forgetting. Specifically, an item-method directed forgetting paradigm was used in conjunction with Remember/Know/New responding to examine the effect of cue duration (1, 3, 5 s) on directed forgetting and remembering in younger and older adults. Results indicated that increased processing time improved performance in both age groups. Critically, older adults exhibited a linear increase in directed remembering performance across all cue durations which was related to individual differences in cognitive reserve. Specifically, those older adults with the highest levels of cognitive functioning showed the greatest memory benefit in the longest cue duration condition. These findings indicate the importance of processing time in accounting for intentional memory performance in older adults.

Assessing socioeconomic inequalities in cognitive impairment among older adults: a study based on a cross-sectional survey in India

Background

The rapidly aging population is a major concern for countries, especially where cognitive health in older age is poor. The study examined the socioeconomic and health-related factors associated with cognitive impairment among older adults and the contribution of those factors to the concentration of low cognitive functioning among older adults from economically poor households.

Methods

Data this study were derived from the “Building Knowledge Base on Population Ageing in India” (BKPAI) survey, which was carried out in seven major states of India. The effective sample size for the analysis was 9176 older adults aged 60 years and above. Results from descriptive and bivariate analysis were reported in the initial stage. Multivariable logistic regression analysis was conducted to explore the associations. Additionally, the concentration index and concentration curve were used to measure socioeconomic inequality in cognitive impairment among older adults. Wagstaff decomposition was employed to explore the key contributors in the concentration index.

Results

Nearly 60% of older adults suffered from cognitive impairment in the study. The likelihood of cognitive impairment were higher among older adults with a low level of self-perceived income sufficiency [coefficient: 0.29; confidence interval (CI): 0.07- 0.52] compared to older adults with higher levels of perceived income status. Older adults with more than 10 years of schooling were less likely to be cognitively impaired [coefficient: -1.27; CI: − 1.50- -1.04] in comparison to those with no education. Cognitive impairment was concentrated among older adults from households with the lowest wealth quintile (concentration index (CCI): − 0.10: p < 0.05). Educational status explained 44.6% of socioeconomic inequality, followed by 31.8% by wealth status and 11.5% by psychological health. Apart from these factors, difficulty in instrumental activities of daily living (3.7%), caste (3.7%), and perceived income sufficiency to fulfil basic needs (3.0%) explained socioeconomic inequality in cognitive impairment among older adults.

Conclusions

Findings suggest that older adults with lower perceived income, lower levels of education, poor physical and mental health, and poor physical and social resources were more likely to be cognitively impaired. Education, wealth and psychological health are major contributors in socioeconomic inequality in late-life cognitive impairment, which may be target areas in future policy formulation to reduce the inequality in cognitive impairment in older Indian adults.

Examining the impact of socioeconomic status, demographic characteristics, lifestyle and other risk factors on adults' cognitive functioning in developing countries: an analysis of five selected WHO SAGE Wave 1 Countries

Background

Though extensive studies have been conducted on assessing the predictors of cognitive functioning among older adults in small community-based samples, very few studies have focused on understanding the impact of socioeconomic status (SES), demographic characteristics and other risk factors such as lifestyle and chronic diseases on the cognitive functioning among adults of all ages in a nationally representative population-based sample across low- and middle-income countries. This study, therefore, seeks to evaluate the impact of SES, demographic characteristics and risk factors on the cognitive functioning of adults across all ages in five selected developing countries.

Methods

Data from 12,430 observations obtained from the WHO Study on Global AGEing and Adult Health (SAGE) Wave 1; consisting of 2,486 observations each for China, Ghana, India, the Russian Federation, and South Africa, were used for the study. A meta-regression and a five-step hierarchical linear regression were used to analyze the data, with cognitive functioning as the dependent variable. Independent variables used in this study include SES; assessed by household income and education, demographic characteristics, other risk factors such as lifestyle, self-reported memory difficulty and chronic diseases.

Results

This study found that SES and lifestyle significantly predicted cognitive functioning in all the five selected countries as obtained by the pooled results of the meta-regression analysis. The hierarchical linear regression results also revealed that demographic characteristics such as age, type of residency, and self-reported memory difficulty significantly impact cognitive functioning in China, Ghana, Russia, and South Africa.

Conclusion

The findings in this study provide new insights for policymakers, caregivers, parents, and individuals, especially those in developing countries, to implement policies and actions targeted at improving SES and eliminating risk factors associated with cognitive decline, as these measures could help improve the cognitive functioning among their populations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12939-022-01622-7.

Predicting Age From Behavioral Test Performance for Screening Early Onset of Cognitive Decline

Background: Neuronal reactions and cognitive processes slow down during aging. The onset, rate, and extent of changes vary considerably from individual to individual. Assessing the changes throughout the lifespan is a challenging task. No existing test covers all domains, and batteries of tests are administered. The best strategy is to study each functional domain separately by applying different behavioral tasks whereby the tests reflect the conceptual structure of cognition. Such an approach has limitations that are described in the article. Objective: Our aim was to improve the diagnosis of early cognitive decline. We estimated the onset of cognitive decline in a healthy population, using behavioral tests, and predicted the age group of an individual. The comparison between the predicted ("cognitive") and chronological age will contribute to the early diagnosis of accelerated aging. Materials and Methods: We used publicly available datasets (POBA, SSCT) and Pearson correlation coefficients to assess the relationship between age and tests results, Kruskal-Wallis test to compare distribution, clustering methods to find an onset of cognitive decline, feature selection to enhance performance of the clustering algorithms, and classification methods to predict an age group from cognitive tests results. Results: The major results of the psychophysiological tests followed a U-shape function across the lifespan, which reflected the known inverted function of white matter volume changes. Optimal values were observed in those aged over 35 years, with a period of stability and accelerated decline after 55-60 years of age. The shape of the age-related variance of the performance of major cognitive tests was linear, which followed the trend of lifespan gray matter volume changes starting from adolescence. There was no significant sex difference in lifelong dynamics of major tests estimates. The performance of the classification model for identifying subject age groups was high. Conclusions: ML models can be designed and utilized as computer-aided detectors of neurocognitive decline. Our study demonstrated great promise for the utility of classification models to predict age-related changes. These findings encourage further explorations combining several tests from the cognitive and psychophysiological test battery to derive the most reliable set of tests toward the development of a highly-accurate ML model.

Association between socioeconomic status and cognitive functioning among older adults in Ghana

OBJECTIVES

Extensive analysis of the associations between socioeconomic status and cognition has been conducted among older adults. However, it is not clear whether associations in high-income countries are similar in low-and middle-income countries. This research aims to investigate the association between the socioeconomic status of older adults in Ghana and their cognitive function by using a sample of older adults that is nationally representative.

METHODS

Data were obtained from a sample of older Ghanaian adults (50+) from the Study of Global AGEing and Adult Health Wave 1 (n = 3710) of the World Health Organization. Objectively, cognition was measured by verbal recall, verbal fluency, forward digit span, and backward digit span, while variations in cognition overall were evaluated against socioeconomic factors using linear regression.

RESULTS

Older age, older women, rural life, increasing memory difficulty, and being diagnosed with stroke were the most significant determinants of impaired cognitive function. Higher education and higher income were significantly associated with a better cognitive function than those with no formal education and low income.

CONCLUSIONS

These results provide new evidence for public health programs in Ghana and other low-and middle-income countries to tackle cognitive impairments in growing populations.

Structural Network Efficiency Predicts Resilience to Cognitive Decline in Elderly at Risk for Alzheimer's Disease

Introduction: Functional imaging studies have demonstrated the recruitment of additional neural resources as a possible mechanism to compensate for age and Alzheimer's disease (AD)-related cerebral pathology, the efficacy of which is potentially modulated by underlying structural network connectivity. Additionally, structural network efficiency (SNE) is associated with intelligence across the lifespan, which is a known factor for resilience to cognitive decline. We hypothesized that SNE may be a surrogate of the physiological basis of resilience to cognitive decline in elderly persons without dementia and with age- and AD-related cerebral pathology.Methods: We included 85 cognitively normal elderly subjects or mild cognitive impairment (MCI) patients submitted to baseline diffusion imaging, liquor specimens, amyloid-PET and longitudinal cognitive assessments. SNE was calculated from baseline MRI scans using fiber tractography and graph theory. Mixed linear effects models were estimated to investigate the association of higher resilience to cognitive decline with higher SNE and the modulation of this association by increased cerebral amyloid, liquor tau or WMHV. Results: For the majority of cognitive outcome measures, higher SNE was associated with higher resilience to cognitive decline (p-values: 0.011-0.039). Additionally, subjects with higher SNE showed more resilience to cognitive decline at higher cerebral amyloid burden (p-values: <0.001-0.036) and lower tau levels (p-values: 0.002-0.015).Conclusion: These results suggest that SNE to some extent may quantify the physiological basis of resilience to cognitive decline most effective at the earliest stages of AD, namely at increased amyloid burden and before increased tauopathy.

Recent Consanguinity and Outbred Autozygosity Are Associated With Increased Risk of Late-Onset Alzheimer's Disease

Prior work in late-onset Alzheimer's disease (LOAD) has resulted in discrepant findings as to whether recent consanguinity and outbred autozygosity are associated with LOAD risk. In the current study, we tested the association between consanguinity and outbred autozygosity with LOAD in the largest such analysis to date, in which 20 LOAD GWAS datasets were retrieved through public databases. Our analyses were restricted to eight distinct ethnic groups: African-Caribbean, Ashkenazi-Jewish European, European-Caribbean, French-Canadian, Finnish European, North-Western European, South-Eastern European, and Yoruba African for a total of 21,492 unrelated subjects (11,196 LOAD and 10,296 controls). Recent consanguinity determination was performed using FSuite v1.0.3, according to subjects' ancestral background. The level of autozygosity in the outbred population was assessed by calculating inbreeding estimates based on the proportion (FROH) and the number (NROH) of runs of homozygosity (ROHs). We analyzed all eight ethnic groups using a fixed-effect meta-analysis, which showed a significant association of recent consanguinity with LOAD (N = 21,481; OR = 1.262, P = 3.6 × 10-4), independently of APOE ∗4 (N = 21,468, OR = 1.237, P = 0.002), and years of education (N = 9,257; OR = 1.274, P = 0.020). Autozygosity in the outbred population was also associated with an increased risk of LOAD, both for F ROH (N = 20,237; OR = 1.204, P = 0.030) and N ROH metrics (N = 20,237; OR = 1.019, P = 0.006), independently of APOE ∗4 [(F ROH, N = 20,225; OR = 1.222, P = 0.029) (N ROH, N = 20,225; OR = 1.019, P = 0.007)]. By leveraging the Alzheimer's Disease Sequencing Project (ADSP) whole-exome sequencing (WES) data, we determined that LOAD subjects do not show an enrichment of rare, risk-enhancing minor homozygote variants compared to the control population. A two-stage recessive GWAS using ADSP data from 201 consanguineous subjects in the discovery phase followed by validation in 10,469 subjects led to the identification of RPH3AL p.A303V (rs117190076) as a rare minor homozygote variant increasing the risk of LOAD [discovery: Genotype Relative Risk (GRR) = 46, P = 2.16 × 10-6; validation: GRR = 1.9, P = 8.0 × 10-4]. These results confirm that recent consanguinity and autozygosity in the outbred population increase risk for LOAD. Subsequent work, with increased samples sizes of consanguineous subjects, should accelerate the discovery of non-additive genetic effects in LOAD.

What does (low) education mean in terms of dementia risk? A systematic review and meta-analysis highlighting inconsistency in measuring and operationalising education

Low education is considered an important modifiable risk factor for dementia worldwide, despite the lack of a formal consensus definition of low education. The primary aim of this systematic review was to document and address the inconsistency in measuring and operationalising education in dementia studies. A secondary aim was to consider the dose of education required to reduce dementia risk. The protocol was registered at PROSPERO with registration ID CRD42018096168. CINAHL, Cochrane, PsycInfo, and Pubmed databases were searched using terms related to education, dementia and/or MCI, and incidence. Studies were eligible for inclusion if a risk ratio for education and any dementia, Alzheimer's Disease (AD), Vascular Dementia (VaD) or Mild Cognitive Impairment (MCI) was reported in a population cognitively healthy at baseline. Sample sizes for 65 studies meeting selection criteria ranged from 152 to 12,881, representing populations from 24 countries. Risk of bias, assessed using a tool designed specifically for dementia risk studies, was found to be medium or low for all studies. There were 23 continuous, 29 dichotomous, and 31 categorical operationalisations of education reported. Random effects meta-analyses from continuous operationalisations suggested each year of education reduced risk by eight percent for AD (95% CI:5-12%) and seven percent for any dementia (95% CI:6-9%). Dichotomous operationalisations indicated an increased risk for low education of 45% (95% CI:29-63%) for any dementia and 85% (95% CI:56-118%) for AD, however definitions of low education were heterogeneous, ranging from zero to 12 years. There were too few studies to produce summary ratios for VaD or MCI. We conclude that, while the evidence of an association between low education and dementia incidence is robust, inconsistency in the definition, measurement and operationalisation of education hinders the translation of this evidence into practical policy recommendations to reduce dementia risk.

Cognitive Reserve Proxies Do Not Differentially Account for Cognitive Performance in Patients with Focal Frontal and Non-Frontal Lesions

OBJECTIVE

Cognitive reserve (CR) suggests that premorbid efficacy, aptitude, and flexibility of cognitive processing can aid the brain's ability to cope with change or damage. Our previous work has shown that age and literacy attainment predict the cognitive performance of frontal patients on frontal-executive tests. However, it remains unknown whether CR also predicts the cognitive performance of non-frontal patients.

METHOD

We investigated the independent effect of a CR proxy, National Adult Reading Test (NART) IQ, as well as age and lesion group (frontal vs. non-frontal) on measures of executive function, intelligence, processing speed, and naming in 166 patients with focal, unilateral frontal lesions; 91 patients with focal, unilateral non-frontal lesions; and 136 healthy controls.

RESULTS

Fitting multiple linear regression models for each cognitive measure revealed that NART IQ predicted executive, intelligence, and naming performance. Age also significantly predicted performance on the executive and processing speed tests. Finally, belonging to the frontal group predicted executive and naming performance, while membership of the non-frontal group predicted intelligence.

CONCLUSIONS

These findings suggest that age, lesion group, and literacy attainment play independent roles in predicting cognitive performance following stroke or brain tumour. However, the relationship between CR and focal brain damage does not differ in the context of frontal and non-frontal lesions.

Interaction between Cognitive Reserve and Biomarkers in Alzheimer Disease

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

Cognitive impairment and its risk factors among Myanmar elderly using the Revised Hasegawa's Dementia Scale: A cross-sectional study in Nay Pyi Taw, Myanmar

Background

Globally, elderly population with impaired cognitive function, such as dementia, has been accelerating, and Myanmar is no exception. However, cognitive function among elderly in Myanmar has rarely been assessed. This study aimed to identify the rate of cognitive impairment and its risk factors among the elderly in Myanmar.

Methods

This cross-sectional study was conducted at rural health centers in Nay Pyi Taw Union Territory, Myanmar, from December 2018 to January 2019. In total, 757 elderly individuals aged 60 years or over (males: 246 [32.5%], females: 511 [67.5%]) were interviewed using a face-to-face method with a pre-tested questionnaire. Descriptive statistics and multivariable logistic regression analyses were performed.

Results

The rate of impaired cognitive function among participants was 29.9% (males: 23.6%; females: 32.9%). The following participants were more likely to present cognitive impairment: those aged 70–79 years (adjusted odds ratio [AOR] = 1.8; 95% confidence interval [CI]: 1.19–2.70) and 80 years or older (AOR = 3.9; 95% CI: 2.25–6.76); those who were illiterate (AOR = 9.1; 95% CI: 3.82–21.51); and those dependent on family members (AOR = 1.6; 95% CI: 1.04–2.44). The elderly livening with their families and those who reported having good health (AOR = 0.7; 95% CI: 0.44–0.99) were less likely to have cognitive impairment.

Conclusion

Using the HDS-R Myanmar version, this study reported that there out of five elderly participants had cognitive impairment, and its risk factors, altering policy makers that Myanmar needs to prepare for adequate healthcare services and social support for elderly with cognitive impairment. Future research should be performed not only to detect general cognitive impairment but also to differentiate specific cognitive domains impairments among Myanmar elderly. Longitudinal studies are needed to observe the causal and protective factors associated with cognitive impairments in Myanmar.

Probing the relationship between late endogenous ERP components with fluid intelligence in healthy older adults

The world population is rapidly aging, bringing together the necessity to better understand the advancing age. This characterization may be used to aid early diagnosis and to guide individually-tailored interventions. While some event-related potential (ERP) components, such as the P300 and late positive complex (LPC), have been associated with fluid intelligence (Gf) in young population; little is known whether these associations hold for older people. Therefore, the main goal of this study was to assess whether these ERP components are associated with Gf in the elderly. Fifty-seven older adults performed a continuous performance task (CPT) and a visual oddball paradigm while EEG was recorded. Participants were divided into two groups, according to their performance in the Raven’s Advanced Progressive Matrices test: high-performance (HP) and low-performance (LP). Results showed that the HP group, compared to the LP group, had higher LPC amplitudes in the CPT and shorter P300 latencies in the oddball task, highlighting the role of ERP components as a potential electrophysiological proxy of Gf abilities in the elderly.

The effects of occupational exposure to manganese fume on neurobehavioral and neurocognitive functions: An analytical cross-sectional study among welders

This study aimed to measure concentrations of manganese fume in breathing zone (BZ) and blood among welders to assess neurocognitive and neurobehavioral functions among them. In this study 38 welders and 27 administrative employees participated. Q16 questionnaire was used to evaluate neurobehavioral symptoms. The computerized Stroop test and Continuous Performance Test (CPT) were used to assess neurocognitive functions. Sampling and analysis of manganese fumes in the BZ and blood samples were performed according to NIOSH-7300 and NIOSH-8005 methods, respectively. Average concentration of manganese in the welders' BZ and blood was 0.81 ± 0.21 mg/m³ and 18.33 ± 5.84 µg/l. Frequency of neurobehavioral symptoms was significantly higher in welders compared with control group. Spearman correlation test showed a moderate correlation between Mn concentrations in the BZ and blood Mn levels (r_s = 0.352). There were statistical moderate and strong correlations between the frequency of neurobehavioral symptoms and manganese concentrations in the BZ (r=0.504) and blood Mn levels (r=0.643).The Pearson correlation coefficient (r=0.433-0.690) obtained on the psychological tests showed a moderate to strong correlation between manganese concentrations in the welders' BZ and blood and some indices of the Stroop test and CPT. The results of this study can confirm the effect of manganese inhalation on creating neurobehavioral and neurocognitive impairments in welders.

Socio-economic status and dementia onset among older Japanese: A 6-year prospective cohort study from the Japan Gerontological Evaluation Study

OBJECTIVES

Lower socio-economic status (SES) may be associated with dementia later in life, but there is inconsistent evidence supporting this claim. We aim to examine the association between three SESs (education, job, and income indicators) and dementia onset in older adults.

METHODS

Study design was a 6-year prospective cohort study. Participants included a total of 52 063 community-dwelling adults aged 65 years or older without long-term care needs from the Japan Gerontological Evaluation Study. Outcome variable was dementia onset. Explanatory variables were educational years, the longest job held, and equivalised household income. We performed Cox proportional hazard analysis by gender with multiple imputation.

RESULTS

During the follow-up period, 10.5% of participants acquired dementia. The adjusted risks of dementia incidence of the participants with less than 6 years of education were 1.34 times (95% confidence interval [CI], 1.04-1.73) in men and 1.21 (1.00-1.45) times in women higher than those with more than 13 years of education. Females with less than 1.99 million yen (hazard ratio = 0.83, 0.72-0.96) of equivalised income were less likely to acquire dementia than those with four million yen or higher.

CONCLUSIONS

Educational attainment had a robust impact on dementia onset compared with the other SES factors in both genders of older Japanese people. Securing an education for children could be crucial to prevent dementia later in life. The longest job held was less likely to be risks of dementia incidence, compared with the other two factors.

Lifecourse epidemiology matures: Commentary on Zhang et al. "Early-life socioeconomic status, adolescent cognitive ability, and cognition in late midlife"

The effect of education on late life cognition has attracted substantial attention in lifecourse epidemiology, in part because of its relevance for understanding the effect of education on dementia. Although numerous studies document an association between education and later life cognition, these studies are potentially confounded by early life socioeconomic position and cognition. Good measures of these early life constructs are rarely available in data sets assessing cognition in late life. A further body of evidence has taken advantage of compulsory schooling law (CSL) instrumental variables (IV), although these estimates have been criticized based on questions about the validity of CSL IVs. In this issue of the Journal, Zhang et al. took advantage of the Wisconsin Longitudinal Study to control for both prospectively measured adolescent IQ and early life socioeconomic status in an analysis evaluating the effect of education on cognitive scores in late middle age (Zhang et al., 2019; IN THIS ISSUE). Their results indicate a moderate effect of each additional year of education on later life cognition, of approximately 0.1-0.15 standard deviations per year of schooling. These estimates are remarkably aligned with findings from prior observational designs and from the CSL IV studies. Although criticisms of any individual study are plausible, this new study complements the body of prior evidence to provide compelling evidence for the benefits of education on late life cognition.

Differential Associations Between Volumes of Atrophic Cortical Brain Regions and Memory Performances in Early and Late Mild Cognitive Impairment

Background

Early and late mild cognitive impairment (MCI) patients have been reported to have a distinctive prognosis of converting to Alzheimer’s disease.

Objective

To evaluate the difference in gray matter volume and assess the association between cognitive function evaluated by comprehensive cognitive function test, and cortical thickness across healthy controls (HCs) (n = 37), early (n = 30), and late MCI patients (n = 35).

Methods

Differences in gray matter volume were evaluated by whole brain voxel-based morphometry across the groups. Multiple regression analysis was used to analyze group by memory performance interactions for the normalized gray matter volume.

Results

The early MCI group showed reduced gray matter volume in the right middle temporal gyrus in comparison to the HC group. The late MCI group displayed atrophy in the left parahippocampal gyrus in comparison to the HC group. Late MCI patients exhibited a decreased gray matter volume in the left fusiform gyrus in comparison to patients in the early MCI group (Monte Carlo simulation corrected p < 0.01, Tukey post hoc tests). Furthermore, there was a significant group (HC vs. early MCI) by memory performance interaction for the normalized cortical volume of the right middle temporal gyrus. Additionally, a significant group (early MCI vs. late MCI) by memory performance interaction was found for the normalized gray matter volume of the left fusiform gyrus (p < 0.001).

Conclusion

Early and late MCI patients showed distinctive associations of gray matter volumes in compensatory brain regions with memory performances. The findings can contribute to a better understanding of the structural changes in compensatory brain regions to elucidate memory decline in the trajectory of the subdivided prodromal stages of the Alzheimer’s disease (AD).

Sex-specific relationship of cardiometabolic syndrome with lower cortical thickness

OBJECTIVE

To investigate whether cardiometabolic factors were associated with age-related differences in cortical thickness in relation to sex.

METHODS

In this cross-sectional study, we enrolled 1,322 cognitively normal elderly (≥65 years old) individuals (774 [58.5%] men, 548 [41.5%] women). We measured cortical thickness using a surface-based analysis. We analyzed the associations of cardiometabolic risk factors with cortical thickness using multivariate linear regression models after adjusting for possible confounders and interactions with age.

RESULT

Among women, hypertension (β = -1.119 to -0.024, p < 0.05) and diabetes mellitus (β = -0.920, p = 0.03) were independently associated with lower mean cortical thickness. In addition, there was an interaction effect between obesity (body mass index [BMI] ≥27.5 kg/m²) and age on cortical thickness in women (β = -0.324 to -0.010, p < 0.05), suggesting that age-related differences in cortical thickness were more prominent in obese women compared to women with normal weight. Moreover, low education level (<6 years) was correlated with lower mean cortical thickness (β = -0.053 to -0.046, p < 0.05). Conversely, among men, only being underweight (BMI ≤18.5 kg/m², β = -2.656 to -0.073, p < 0.05) was associated with lower cortical thickness.

CONCLUSIONS

Our findings suggest that cortical thickness is more vulnerable to cardiometabolic risk factors in women than in men. Therefore, sex-specific prevention strategies may be needed to protect against accelerated brain aging.

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

BACKGROUND

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

DISCUSSION

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

CONCLUSION

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

Cognitive reserve

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

Gender difference in cognitive health among older Indian adults: A cross-sectional multilevel analysis

This study assesses the gender gap in cognitive health among older adults in India and examines the extent to which individual, household and state level characteristics contribute to the male-female difference in cognitive health. The study is based on 6548 women and men who participated in the WHO Study on Global AGEing and Adult Health conducted in six states in India during 2007-08. Multilevel ordinary least square regression was used to examine the gender difference in cognitive health, adjusting for individual, household, health behavior and state-level variables. A composite cognitive score (CCS) was calculated by combining z-scores of five individual cognitive tests. Results suggest that CCS is worse among women than among men after adjusting for individual and state level factors. The largest reduction in the gender gap in CCS was observed when adjusting for education, followed by other individual factors such as marital status, individual height, caste, religion, tobacco consumption and chronic health status. Although state level urbanization and female workforce participation rate were significantly associated with CCS, these characteristics did not contribute to the reduction of gender difference in CCS. This study extends the current knowledge of women's disadvantage in cognitive health, demonstrating that individual level characteristics remain key determinants of gender difference in cognition among older adults in India. Importantly, this relationship holds in the context of very large cross-state variations in cognitive health and its determinants.

The association between educational parameters and a cognitive screening measure in older blacks

ABSTRACTBackground:To expand on prior literature by examining how various education parameters (performance-based reading literacy, years of education, and self-rated quality of education) relate to a cognitive screening measure's total and subscale scores of specific cognitive abilities.

METHODS

Black adults (age range: 55-86) were administered self-rated items years of education and quality of education, and a measure of performance-based reading literacy. The Mini-Mental State Examination (MMSE) was used to screen for overall cognitive functioning as well as performance on specific cognitive abilities.

RESULTS

Sixty-nine percent of the sample had reading grade levels that were less than their reported years of education. Lower years of education and worse reading literacy are associated with poorer MMSE performance, particularly on the attention and calculation subscales.

CONCLUSIONS

Years of education, a commonly used measure for education, may not be reflective of Black adults' educational experiences/qualities. Thus, it is important to account for the unique educational experiences of adults that could influence their MMSE performance. Incorporating quality and quantity of education will provide a more comprehensive understanding of the individual's performance on cognitive measures, specifically as it relates to sociocultural differences.

Occupational Attainment as Risk Factor for Progression from Mild Cognitive Impairment to Alzheimer's Disease: A CREDOS Study

High occupational attainment has been known as a marker of cognitive reserve. Previous studies in the general population have shown that high occupational attainment is associated with reduced risk of Alzheimer's disease (AD). However, few studies have assessed the effect of occupational attainment on the clinical course of mild cognitive impairment (MCI). In this study, we evaluated whether individuals with high occupational attainment show more frequent progression from MCI to AD. Participants (n = 961) with MCI were recruited from a nationwide, hospital-based multi-center cohort, and were followed for up to 60 months (median: 17.64, interquartile range [12.36, 29.28]). We used Cox regression for competing risks to analyze the effect of occupational attainment on development of AD, treating dementia other than AD as a competing risk. Among the 961 individuals with MCI, a total of 280 (29.1%) converted to dementia during the follow-up period. The risk of progression to AD was higher in the individuals with high occupational attainment after controlling for potential confounders (hazard ratio = 1.83, 95% confidence interval = 1.25-2.69, p = 0.002). High occupational attainment in individuals with MCI is an independent risk factor for higher progression rate of MCI to AD. This result suggests that the protective effect of high occupational attainment against cognitive decline disappears in the MCI stage, and that careful assessment of occupational history can yield important clinical information for prognosis in individuals with MCI.

The development of a stochastic mathematical model of Alzheimer's disease to help improve the design of clinical trials of potential treatments

Alzheimer's disease (AD) is a neurodegenerative disorder characterised by a slow progressive deterioration of cognitive capacity. Drugs are urgently needed for the treatment of AD and unfortunately almost all clinical trials of AD drug candidates have failed or been discontinued to date. Mathematical, computational and statistical tools can be employed in the construction of clinical trial simulators to assist in the improvement of trial design and enhance the chances of success of potential new therapies. Based on the analysis of a set of clinical data provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI) we developed a simple stochastic mathematical model to simulate the development and progression of Alzheimer's in a longitudinal cohort study. We show how this modelling framework could be used to assess the effect and the chances of success of hypothetical treatments that are administered at different stages and delay disease development. We demonstrate that the detection of the true efficacy of an AD treatment can be very challenging, even if the treatment is highly effective. An important reason behind the inability to detect signals of efficacy in a clinical trial in this therapy area could be the high between- and within-individual variability in the measurement of diagnostic markers and endpoints, which consequently results in the misdiagnosis of an individual's disease state.

Comparing Alternative Effect Decomposition Methods: The Role of Literacy in Mediating Educational Effects on Mortality

BACKGROUND

Inverse odds ratio weighting, a newly proposed tool to evaluate mediation in exposure-disease associations, may be valuable for a host of research questions, but little is known about its performance in real data. We compare this approach to a more conventional Baron and Kenny type of decomposition on an additive hazards scale to estimate total, direct, and indirect effects using the example of the role of literacy in mediating the effects of education on mortality.

METHODS

Health and Retirement Study participants born in the United States between 1900 and 1947 were interviewed biennially for up to 12 years (N = 17,054). Literacy was measured with a brief vocabulary assessment. Decomposition estimates were derived based on Aalen additive hazards models.

RESULTS

A 1 standard deviation difference in educational attainment (3 years) was associated with 6.7 fewer deaths per 1000 person-years (β = -6.7, 95% confidence interval [CI]: -7.9, -5.4). Of this decrease, 1.3 fewer deaths (β = -1.3, 95% CI: -4.0, 1.2) were attributed to the literacy pathway (natural indirect), representing 19% of the total effect. Baron and Kenny estimates were consistent with inverse odds ratio weighting estimates but were less variable (natural indirect effect: -1.2 [95% CI: -1.7, -0.69], representing 18% of total effect).

CONCLUSION

In a cohort of older Americans, literacy partially mediated the effect of education on mortality. See Video Abstract at http://links.lww.com/EDE/B78.

The relationship of individual social activity and cognitive function of community Chinese elderly: a cross-sectional study

BACKGROUND

The prevention of cognitive impairment is a crucial public health issue, and leisure activities have been studied as the strategy of the cognitive preservation. The aim of the study was to explore the possible relationship between social activity and cognitive function among community-dwelling Chinese elderly in two big cities of Southern China.

PARTICIPANTS AND METHODS

Altogether, 557 nondemented older adults aged 60 years and older (73.4±6.5 years) were recruited in the social centers in Hong Kong and Guangzhou. A leisure activity questionnaire was used to measure the social activity participation. Cognitive function was examined using a neuropsychological battery. The association between social activity and cognitive function was analyzed using the multiple linear regression analysis.

RESULTS

Social activities had a weak relationship with cognitive performance when measured in terms of overall participation. Attending an interest class had significant association with the Cantonese version of Mini Mental State Examination, the word list learning test, the delayed recall test, and the trail making test. Religious activity showed significant association with the word list learning test and the digit vigilance test. Singing had significant association with the Category Verbal Fluency Test (CVFT) and the trail making test.

CONCLUSION

Some individual social activity items may be associated with better cognitive function among the community Chinese elderly independently of other factors.

Education as a Protective Factor Moderating the Effect of Depression on Memory Impairment in Elderly Women

OBJECTIVE

The cognitive reserve theory explicates individual differences observed in the clinical manifestation of dementia despite similar brain pathology. Education, a popular proxy of the cognitive reserve, has been shown to have protective effects delaying the onset of clinical symptoms including memory. This study was conducted to test whether education can moderate the negative effect of depressive mood on memory performance in elderly women residing in the community.

METHODS

29 elderly "unschooled" female (less than 6 years of formal education) and 49 "schooled" female (6 or more years) people were compared with regard to association between depressive mood and verbal memory functioning, which were measured by the Geriatric Depression Scale and the Elderly Verbal Learning Test, respectively.

RESULTS

The results showed that completing or receiving more than primary school education significantly reduced the negative association between depressive mood and memory performance. Participants who did not complete primary schooling showed a decline in memory test scores depending on the level of depressive mood; whereas participants who have completed or received more than primary education displayed relatively stable memory function despite varying level of depressive mood.

CONCLUSION

Our findings imply that education in early life may have protective effects against memory impairment related to elderly depression.

Potential Factors Associated with Cognitive Improvement of Individuals Diagnosed with Mild Cognitive Impairment or Dementia in Longitudinal Studies

Despite the progressive nature of Alzheimer's disease and other dementias, it is observed that many individuals that are diagnosed with mild cognitive impairment (MCI) in one clinical assessment, may return back to normal cognition (CN) in a subsequent assessment. Less frequently, such 'back-transitions' are also observed in people that had already been diagnosed with later stages of dementia. In this study, an analysis was performed on two longitudinal cohort datasets provided by 1) the Alzheimer's Disease Neuroimaging Initiative (ADNI) and 2) the National Alzheimer's Coordinating Centre (NACC). The focus is on the observed improvement of individuals' clinical condition recorded in these datasets to explore potential associations with different factors. It is shown that, in both datasets, transitions from MCI to CN are significantly associated with younger age, better cognitive function, and the absence of ApoE ɛ4 alleles. Better cognitive function and in some cases the absence of ApoE ɛ4 alleles are also significantly associated with transitions from types of dementia to less severe clinical states. The effect of gender and education is not clear-cut in these datasets, although highly educated people who reach MCI tend to be more likely to show an improvement in their clinical state. The potential effect of other factors such as changes in symptoms of depression is also discussed. Although improved clinical outcomes can be associated with many factors, better diagnostic tools are required to provide insight into whether such improvements are a result of misdiagnosis, and if they are not, whether they are linked to improvements in the underlying neuropathological condition.

Factors influencing accuracy of cortical thickness in the diagnosis of Alzheimer's disease

There is great value to use of structural neuroimaging in the assessment of Alzheimer's disease (AD). However, to date, predictive value of structural imaging tend to range between 80% and 90% in accuracy and it is unclear why this is the case given that structural imaging should parallel the pathologic processes of AD. There is a possibility that clinical misdiagnosis relative to the gold standard pathologic diagnosis and/or additional brain pathologies are confounding factors contributing to reduced structural imaging classification accuracy. We examined potential factors contributing to misclassification of individuals with clinically diagnosed AD purely from cortical thickness measures. Correctly classified and incorrectly classified groups were compared across a range of demographic, biological, and neuropsychological data including cerebrospinal fluid biomarkers, amyloid imaging, white matter hyperintensity (WMH) volume, cognitive, and genetic factors. Individual subject analyses suggested that at least a portion of the control individuals misclassified as AD from structural imaging additionally harbor substantial AD biomarker pathology and risk, yet are relatively resistant to cognitive symptoms, likely due to "cognitive reserve," and therefore clinically unimpaired. In contrast, certain clinical control individuals misclassified as AD from cortical thickness had increased WMH volume relative to other controls in the sample, suggesting that vascular conditions may contribute to classification accuracy from cortical thickness measures. These results provide examples of factors that contribute to the accuracy of structural imaging in predicting a clinical diagnosis of AD, and provide important information about considerations for future work aimed at optimizing structural based diagnostic classifiers for AD.

Educational status influences cognitive-motor learning in older adults: going to university provides greater protection against aging than going to high school

OBJECTIVE

To investigate if middle-aged and older adults with a higher education would differ from those with an average education in cognitive-motor tasks involving lower limb function.

METHODS

A walking version of the Trail Making Test (Walking Executive Function Task, [WEFT]) was used. Eighty volunteers (40: 50-65 years; 40: 66-80 years) were subdivided into average (6-11years of education) and higher education (12-17 years). They received two training sessions (session 1: eight repetitions, session 2: four repetitions), with a one week-interval between them. The Timed Up and Go (TUG) test was performed before and after the training.

RESULTS

Volunteers with an average education showed longer times on the WEFT than those with a higher education. Older adults showed lower retention than middle-aged adults (p < 0.001). The TUG was faster after the WEFT training (p < 0.001).

CONCLUSION

The impact of education was observed when locomotion was associated with cognitive tasks. Average education resulted in poorer performance and learning than higher education, mainly in older adults. Gait speed increased after training.

Home and family in cognitive rehabilitation after brain injury: Implementation of social reserves

The focus of the present article is the home and family environment of patients suffering acquired brain injury. In order to obtain the optimal outcome of posttraumatic cognitive rehabilitation it is important (a) to obtain a sufficient intensity of rehabilitative training, (b) to achieve the maximum degree of generalization from formalized training to the daily environment of the patient, and (c) to obtain the best possible utilization of "cognitive reserves" in the form of cognitive abilities and "strategies" acquired pretraumatically. Supplementing the institution-based cognitive training with (potentially computer-based) home-based training these three goals may more easily be met. Home-based training supports a higher intensity of training. Training in the home environment also allows better utilization of cognitive strategies acquired pretraumatically and more direct transfer of training results from formalized training to activities of daily living of the patient.

Neurocognitive Deficits and Effects of Cognitive Reserve in Mild Cognitive Impairment

BACKGROUND/AIMS

Mild cognitive impairment (MCI) is a frequent syndrome in the older population, which involves an increased risk to develop Alzheimer's disease (AD). The latter can be modified by the cognitive reserve, which can be operationalized by the length of school education. MCI can be differentiated into four subtypes according to the cognitive domains involved: amnestic MCI, multiple-domain amnestic MCI, non-amnestic MCI and multiple-domain non-amnestic MCI. While neurocognitive deficits are a constituent of the diagnosis of these subtypes, the question of how they refer to the cognitive reserve still needs to be clarified.

METHODS

We examined neuropsychological deficits in healthy controls, patients with MCI and patients with mild AD (n = 485) derived from a memory clinic. To reduce the number of neuropsychological variables, a factor analysis with varimax rotation was calculated. In a second step, diagnostic groups including MCI subtypes were compared with respect to their clinical and neuropsychological characteristics including cognitive reserve.

RESULTS

Most MCI patients showed the amnestic multiple-domain subtype followed by the pure amnestic subtype, while the non-amnestic subtypes were rare. The amnestic subtype displayed a significantly higher level of cognitive reserve and higher MMSE scores than the amnestic multiple-domain subtype, which was in most cases characterized by additional psychomotor and executive deficits.

CONCLUSIONS

These findings confirm earlier reports revealing that the amnestic multiple-domain subtype is the most frequent one and indicating that a high cognitive reserve may primarily prevent psychomotor and executive deficits in MCI.

Cardiovascular Pharmacogenomics and Cognitive Function in Patients with Schizophrenia

The authors sought to examine the impact of multiple risk alleles for cognitive dysfunction and cardiovascular disease risk on cognitive function and to determine if these relationships varied by cognitive reserve (CR) or concomitant medication use in patients with schizophrenia. They conducted a cross-sectional study in ambulatory mental health centers. A total of 122 adults with a schizophrenia spectrum diagnosis who were maintained on a stable antipsychotic regimen for at least 6 months before study enrollment were included. Patients were divided into three CR groups based on years of formal education: no high school completion or equivalent (low-education group [18 patients]), completion of high school or equivalent (moderate-education group [36 patients], or any degree of post-high school education (high-education group [68 patients]). The following pharmacogenomic variants were genotyped for each patient: AGT M268T (rs699), ACE insertion/deletion (or ACE I/D, rs1799752), and APOE ε2, ε3, and ε4 (rs429358 and rs7412). Risk allele carrier status (identified per gene as AGT M268 T carriers, ACE D carriers, and APOE ε4 carriers) was not significantly different among CR groups. The Brief Assessment of Cognition in Schizophrenia (BACS) scale was used to assess cognitive function. The mean ± SD patient age was 43.9 ± 11.6 years. Cardiovascular risk factors such as hypertension and hyperlipidemia diagnoses, and use of antihypertensive and lipid-lowering agents, did not significantly differ among CR groups. Mixed modeling revealed that risk allele carrier status was significantly associated with lower verbal memory scores for ACE D and APOE ε4 carriers, but AGT T carrier status was significantly associated with higher verbal memory scores (p=0.0188, p=0.0055, and p=0.0058, respectively). These results were only significant in the low-education group. In addition, medication-gene interactions were not significant predictors of BACS scores. ACE D and APOE ε4 carrier status, independent of medication use, was associated with lower verbal memory scores in patients with schizophrenia who had relatively lower CR, as identified by formal education. These results suggest that increasing CR may be protective against cognitive impairment that may be worsened by select cardiovascular risk alleles in patients with schizophrenia.

Physical Activity and Cognitive Function of Long-Distance Walkers: Studying Four Days Marches Participants

Studies show physical activity to be beneficial for cognitive function. However, studies usually included individuals who were not particularly inclined to exercise. Following research among master athletes, we examined associations between physical activity and cognitive function in participants of the International Nijmegen Four Days Marches. These individuals are also inclined to exercise. On 4 consecutive days >40,000 participants walk a daily distance of 30-50 km (120-200 km or 75-125 miles in total). Four Days Marches participants and less active or inactive control participants from the Nijmegen Exercise Study were examined. Self-reported current and lifelong physical activities were quantified in Metabolic Equivalent of Task minutes/day, and training walking speed was estimated in km/h. Cognitive functioning in the domains of working memory, executive function, and visuospatial short-term memory was assessed using the validated Brain Aging Monitor. Data from 521 participants (mean age 54.7, standard deviation 12.9) showed neither positive associations between lifelong physical activity and working memory, executive function, and visuospatial short-term memory nor positive associations between current physical activity and cognitive functioning in these domains (p-values >0.05). However, a positive association between training walking speed and working memory was revealed (age adjusted β = 0.18, p-value <0.01). Walking speed as a surrogate marker of fitness, but not lifelong and current physical activity levels was associated with cognitive function. Therefore, walking speed deserves more attention in research aimed at unraveling associations between physical activity and cognitive function.

Population Normative Data for the CERAD Word List and Victoria Stroop Test in Younger- and Middle-Aged Adults: Cross-Sectional Analyses from the Framingham Heart Study

BACKGROUND/STUDY CONTEXT

To provide baseline normative data on tests of verbal memory and executive function for nondemented younger- and middle-aged adults.

METHODS

The Consortium to Establish a Registry for Alzheimer's Disease word list memory task (CERAD-WL) and Victoria Stroop Test (VST) were administered to 3362 Framingham Heart Study (FHS) volunteer participants aged 24-78 years. Analyses of the effects of age, gender, and education were conducted. Normative data on traditional measures and error responses are reported for each test.

RESULTS

Traditional measures were significantly associated with both age and education in this cohort. Error responses also evidenced significant age and education effects.

CONCLUSION

These data provide a normative comparison for assessment of verbal memory and executive functioning capabilities in younger- and middle-aged adults and may be utilized as a tool for preclinical studies of disease in this population.

Delirium in elderly patients: association with educational attainment

OBJECTIVE

Among cognitive reserve markers, educational attainment is the most widely studied, with several studies establishing a strong association with risk of dementia. However, it has not yet been fully examined in delirium. This study aims to analyse the relationship between educational attainment and delirium.

METHODS

The study included elderly hospitalised patients admitted (≥48 h) into an intermediate care unit (IMCU) of Intensive Care Medicine Service. Exclusion criteria were as follows: Glasgow Coma Scale (total≤11), blindness/deafness, inability to communicate or to speak Portuguese. The European Portuguese Version of the Confusion Assessment Method (CAM) was used for delirium assessment.

RESULTS

The final sample (n=157) had a mean age of 78.8 (SD=7.6) the majority being female (52.2%), married (51.5%) and with low educational level (49%). According to CAM, 21% of the patients had delirium. The delirium group presented the fewest years of education (median 1 vs. 4), with statistical significance (p=0.003). Delirium was more frequent among male patients [odds ratio (OR) 0.32; 95% confidence interval (CI) 0.12-0.86; p=0.023], as well as those patients with lower education (OR 0.76; 95% CI 0.62-0.95; p=0.016), and with respiratory disease (OR 3.35; 95% CI 1.20-9.33; p=0.020), after controlling for age and medication.

CONCLUSION

Similar to previous studies, these findings point to a negative correlation between education and delirium. This study appears as an attempt to contribute to the knowledge about the role of cognitive reserve in risk of delirium, particularly because is the first one that has been carried out in an IMCU, with lower educated elderly patients. Further studies are needed to clarify this relationship considering other markers (e.g. cognitive activities), which can contribute to the definition of preventive strategies.

Midlife managerial experience is linked to late life hippocampal morphology and function

An active cognitive lifestyle has been suggested to have a protective role in the long-term maintenance of cognition. Amongst healthy older adults, more managerial or supervisory experiences in midlife are linked to a slower hippocampal atrophy rate in late life. Yet whether similar links exist in individuals with Mild Cognitive Impairment (MCI) is not known, nor whether these differences have any functional implications. 68 volunteers from the Sydney SMART Trial, diagnosed with non-amnestic MCI, were divided into high and low managerial experience (HME/LME) during their working life. All participants underwent neuropsychological testing, structural and resting-state functional MRI. Group comparisons were performed on hippocampal volume, morphology, hippocampal seed-based functional connectivity, memory and executive function and self-ratings of memory proficiency. HME was linked to better memory function (p = 0.024), mediated by larger hippocampal volume (p = 0.025). More specifically, deformation analysis found HME had relatively more volume in the CA1 sub-region of the hippocampus (p < 0.05). Paradoxically, this group rated their memory proficiency worse (p = 0.004), a result correlated with diminished functional connectivity between the right hippocampus and right prefrontal cortex (p < 0.001). Finally, hierarchical regression modelling substantiated this double dissociation.

Cognitive reserve and cognitive performance of patients with focal frontal lesions

The Cognitive reserve (CR) hypothesis was put forward to account for the variability in cognitive performance of patients with similar degrees of brain pathology. Compensatory neural activity within the frontal lobes has often been associated with CR. For the first time we investigated the independent effects of two CR proxies, education and NART IQ, on measures of executive function, fluid intelligence, speed of information processing, verbal short term memory (vSTM), naming, and perception in a sample of 86 patients with focal, unilateral frontal lesions and 142 healthy controls. We fitted multiple linear regression models for each of the cognitive measures and found that only NART IQ predicted executive and naming performance. Neither education nor NART IQ predicted performance on fluid intelligence, processing speed, vSTM or perceptual abilities. Education and NART IQ did not modify the effect of lesion severity on cognitive impairment. We also found that age significantly predicted performance on executive tests and the majority of our other cognitive measures, except vSTM and GNT. Age was the only predictor for fluid intelligence. This latter finding suggests that age plays a role in executive performance over and above the contribution of CR proxies in patients with focal frontal lesions. Overall, our results suggest that the CR proxies do not appear to modify the relationship between cognitive impairment and frontal lesions.

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Effect of cognitive reserve (CR) proxies in focal unilateral lesions.

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NART IQ accounts for a larger proportion of variance in executive and naming skills.

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Age predicts performance on executive, fluid intelligence, speed and perception tests.

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Education and NART IQ did not modify the effect of lesion severity on cognitive impairment.

The role of pre-morbid intelligence and cognitive reserve in predicting cognitive efficiency in a sample of Italian elderly

BACKGROUND

Models of cognitive reserve in aging suggest that individual's life experience (education, working activity, and leisure) can exert a neuroprotective effect against cognitive decline and may represent an important contribution to successful aging.

AIM

The objective of the present study is to investigate the role of cognitive reserve, pre-morbid intelligence, age, and education level, in predicting cognitive efficiency in a sample of healthy aged individuals and with probable mild cognitive impairment.

METHODS

Two hundred and eight aging participants recruited from the provincial region of Bari (Apulia, Italy) took part in the study. A battery of standardized tests was administered to them to measure cognitive reserve, pre-morbid intelligence, and cognitive efficiency. Protocols for 10 participants were excluded since they did not meet inclusion criteria, and statistical analyses were conducted on data from the remaining 198 participants. A path analysis was used to test the following model: age, education level, and intelligence directly influence cognitive reserve and cognitive efficiency; cognitive reserve mediates the influence of age, education level, and intelligence on cognitive efficiency.

RESULTS

Cognitive reserve fully mediates the relationship between pre-morbid intelligence and education level and cognitive efficiency, while age maintains a direct effect on cognitive efficiency.

DISCUSSION

Cognitive reserve appears to exert a protective effect regarding cognitive decline in normal and pathological populations, thus masking, at least in the early phases of neurodegeneration, the decline of memory, orientation, attention, language, and reasoning skills.

CONCLUSIONS

The assessment of cognitive reserve may represent a useful evaluation supplement in neuropsychological screening protocols of cognitive decline.

Social-Economic Status and Cognitive Performance among Chinese Aged 50 Years and Older

Background

Numerous population-based studies have suggested that socio-economic status (SES) is associated with cognitive performance, but few nationally representative epidemiological studies on cognitive performance with a large sample of older adults are available in China. And many studies explore the factors associated with cognitive performance, mainly focusing on individual level and more rarely on multiple levels that include the individual and community.

Methods

This study uses SAGE-China Wave 1 data which consisted of 13,157 adults aged 50 years and older to explore socioeconomic inequalities in the cognitive performance from a multilevel perspective (individual and community levels). The overall cognition score was based on the seven separate components of the cognition tests, including the four verbal recall trials, the verbal fluency test, the forward digit span test and the backward digit span test. Factor analysis was applied to evaluate and generate a single overall score. A two-level hierarchical linear model was used to evaluate the association between SES at these two levels and the overall cognition score adjusted for age, sex and marital status.

Results

At individual level, years of education was significantly associated with overall cognition score for both urban and rural dwellers. At the community level, a positive association was obtained between median household income and median years of education and overall cognition score among urban participants.

Conclusion

A significant association between SES at both individual-level and community-level (only for urban area) and cognitive performance were found in this study of a national sample of 13,157 Chinese aged 50 years and older, even after adjusting for demographic characteristics. Identifying community-based SES variables that are associated with cognitive performance in the older population provides further evidence for the need to address community characteristics associated with deprivation.

Risk for developing dementia among patients with posttraumatic stress disorder: A nationwide longitudinal study

OBJECTIVES

Previous studies suggested a relationship between posttraumatic stress disorder (PTSD) in the specific population (i.e., war survivors and veterans) and subsequent dementia risk. However, whether patients with PTSD in the general population were at an increased risk for developing dementia in later life remained unclear.

METHODS

The Cox regression analysis was performed using data from the Taiwan National Health Insurance Research Database. The study sample comprised 1750 patients diagnosed with PTSD between 2001 and 2009 and 7000 age-/sex-matched individuals without PTSD. Those who developed dementia during follow-up to the end of 2011 were identified.

RESULTS

After adjusting for demographic data and medical and psychiatric comorbidities, PTSD was an independent risk factor for the risk for subsequent dementia (hazard ratio [HR]=4.37; 95% confidence interval [CI]: 2.53-7.55). There was a dose-dependent relationship between PTSD severity indicated by the frequency of psychiatric clinics visiting of PTSD (times per year) and the risk of subsequent dementia (<5: HR: 2.81, 95% CI: 1.50-5.29; 5-10: 6.90, 95% CI: 3.09-15.40;>10: HR: 18.13, 95% CI: 9.13-36.00). Furthermore, patients with depressive disorder and medical comorbidities, such as cerebrovascular diseases, diabetes mellitus, and head injuries, exhibited a higher risk for developing dementia.

DISCUSSIONS

Our study suggested a significant dose-dependent association between PTSD and its severity and an increased risk of developing dementia later in life. The importance of mental care for trauma victims would increase in the coming century, and our findings broadened another era for the end result of a widely prevalent psychiatric disorder.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

Age-related changes in sleep EEG are attenuated in highly intelligent individuals

Impaired sleep is a frequent complaint in ageing and a risk factor for many diseases. Non-rapid eye movement (NREM) sleep EEG delta power reflects neural plasticity and, in line with age-related cognitive decline, decreases with age. Individuals with higher general intelligence are less affected by age-related cognitive decline or other disorders and have longer lifespans. We investigated the correlation between age and EEG power in 159 healthy human subjects (age range: 17-69 years), and compared an average (IQ<120; N=87) with a high (IQ≥120; N=72) intelligence subgroup. We found less age-related decrease in all-night relative NREM sleep EEG delta power in the high intelligence subgroup. Our results suggest that highly intelligent individuals are less affected by the sleep-related effects of biological ageing, and therefore potentially less at risk for age-related cognitive deficits and other diseases.

Neurocognitive function of lymphoma patients after treatment with chemotherapy

BACKGROUND

Chemotherapy has been shown to cause brain changes and to compromise cognitive function in cancer survivors. Knowledge about this matter is of vital importance for good clinical practice and insights into neurological aging. However, most studies have been conducted among breast cancer patients. Less is known about the effects of chemotherapy on the cognitive function of lymphoma patients.

MATERIAL AND METHOD

We studied patients with non-Hodgkin or Hodgkin lymphoma who had been treated with standard dose chemotherapy or with supplementary high dose chemotherapy when standard dose chemotherapy had been unsuccessful. Age- and sex-matched relatives and friends were invited to participate as control participants. All participants underwent a cognitive examination with a battery of validated neuropsychological tests.

RESULTS

Matching of patients with control participants was found to be successful. Regression analysis did not reveal worse cognitive functioning of patients (N = 106) compared to matched controls (N = 53) on the overall group level (All Bonferroni-Holm corrected p-values >0.05). However, a subgroup of 16% of patients had deviant performance according to a chance-corrected criterion based on Ingraham and Aiken's probability curves, i.e. 1.5 standard deviations below the norm on three of 14 tests. Exploratory analyses showed that this subgroup of patients was lower educated and had lower estimated premorbid intelligence.

CONCLUSION

Chemotherapy may compromise the function of the brain in a subgroup of lymphoma patients. We hypothesize protection of the brain by 'cognitive or brain reserve' as a possible explanation.

Influence of Formal Education on Cognitive Reserve in Patients with Multiple Sclerosis

The concept of cognitive reserve (CR) and its influence on cognitive impairment has attracted increasing interest. One hundred twenty-eight patients with multiple sclerosis (MS) from Southern Germany were evaluated during the years 2000 to 2012. Twenty-seven neuropsychological (NP) tests were applied regarding basic cognitive functions, attention, executive functions, visual perception and construction, memory and learning, problem solving, and language. By this retrospective approach, a comprehensive NP profile of the investigated individuals was established. An effect of timespan of formal education on CR was observed. Enrichment by reading, physical activities, and challenging vocational practices had more profound effects in patients who had undergone a shorter educational period compared to a longer educational period. In summary, our study demonstrates that the advantage of longer formal education periods, compared to shorter formal education periods, can be counterbalanced by high frequencies of reading, physical activities, and challenging vocational practices in patients with MS.