An International Evaluation of Cognitive Reserve and Memory Changes in Early Old Age in 10 European Countries

Change in cognitive performance during seven-year follow-up in midlife is associated with sex, age, and education - The Cardiovascular Risk in Young Finns Study

OBJECTIVE

Sex, age, and education are associated with the level of cognitive performance. We investigated whether these factors modulate the change in cognitive performance in midlife by leveraging the longitudinal data from the Cardiovascular Risk in Young Finns Study (YFS).

METHODS

Participants of the YFS cohort performed a computer-based Cambridge Neuropsychological Test Automated Battery (CANTAB) in 2011 and 2018 (n = 1671, age 41-56 years in 2018). Overall cognitive performance and domains representing learning and memory, working memory, reaction time, and information processing were extracted by common principal component analysis from the longitudinal cognitive data. Linear models adjusted for baseline cognitive performance were used to study the association of sex, age, and education with changes in overall cognitive performance and in the cognitive domains.

RESULTS

Cognitive performance decreased in all domains (overall cognition -0.56 SD, p < 0.001; working memory -0.81 SD, p < 0.001; learning and memory -0.70 SD, p < 0.001; reaction time -0.06 SD, p = 0.019; information processing -0.03 SD, p = 0.016). The decrease in working memory and information processing was greater in females compared to males. Cognitive performance decreased more in older participants in all domains. Education alleviated the decrease in cognitive performance in all domains except reaction time. The beneficial effect of education was greater for males.

CONCLUSIONS

This study describes the natural course of aging-related changes in cognitive performance in midlife, the critical time window for early prevention of clinical cognitive decline. These findings provide a reference for studies focusing on determinants of pathological cognitive decline deviating from normal changes in cognitive performance.

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

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

A nomogram to predict the risk of cognitive impairment in patients with depressive disorder

This study was to describe the cognitive function status in patients with depressive disorder and to construct a nomogram model to predict the risk factors of cognitive impairment in these patients. From October 2019 to February 2021, a total of 141 patients with depressive disorder completed the survey in two hospitals. The Montreal cognitive assessment (MoCA) was used with a cutoff score of 26 to differentiate cognitive impairment. Univariable and multivariable logistic regression analyses were conducted to identify independent risk factors. A nomogram was then constructed based on the results of the multivariable logistic regression analysis. The patients had an average MoCA score of 23.99 ± 3.02. The multivariable logistic regression analysis revealed that age (OR: 1.096, 95% CI: 1.042-1.153, p < 0.001), education (OR: 0.065, 95% CI: 0.016-0.263, p < 0.001), depression severity (OR: 1.878, 95% CI: 1.021-3.456, p = 0.043), and sleep quality (OR: 2.454, 95% CI: 1.400-4.301, p = 0.002) were independent risk factors for cognitive impairment in patients with depressive disorder. The area under receiver operating characteristic (ROC) curves was 0.868 (95% CI: 0.807-0.929), indicating good discriminability of the model. The calibration curve of the model and the Hosmer-Lemeshow test (p = 0.571) demonstrated a well-fitted model with high calibration. Age, education, depression severity, and sleep quality were found to be significant predictors of cognitive function. A nomogram model was developed to predict cognitive impairment in patients with depressive disorder, providing a solid foundation for clinical interventions.

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

Introduction

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

Methods

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

Results

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

Discussion

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

Cohort Changes and Sex Differences After Age 50 in Cognitive Variables in the English Longitudinal Study of Ageing

OBJECTIVES

This paper models cognitive aging, across mid and late life, and estimates birth cohort and sex differences in both initial levels and aging trajectories over time in a sample with multiple cohorts and a wide span of ages.

METHODS

The data used in this study came from the first 9 waves of the English Longitudinal Study of Ageing, spanning 2002-2019. There were n = 76,014 observations (proportion male 45%). Dependent measures were verbal fluency, immediate recall, delayed recall, and orientation. Data were modeled using a Bayesian logistic growth curve model.

RESULTS

Cognitive aging was substantial in 3 of the 4 variables examined. For verbal fluency and immediate recall, males and females could expect to lose about 30% of their initial ability between the ages of 52 and 89. Delayed recall showed a steeper decline, with males losing 40% and females losing 50% of their delayed recall ability between ages 52 and 89 (although females had a higher initial level of delayed recall). Orientation alone was not particularly affected by aging, with less than a 10% change for either males or females. Furthermore, we found cohort effects for initial ability level, with particularly steep increases for cohorts born between approximately 1930 and 1950.

DISCUSSION

These cohort effects generally favored later-born cohorts. Implications and future directions are discussed.

Cognitive reserve and other determinants of cognitive function in older adults: Insights from a community-based cross-sectional study

Background

India will be the home of 323 million elderly persons by 2050. This means a surge in the dependent population primarily due to age-related cognitive decline. Evidence suggests that life course factors may have a modulatory role on cognitive function. The present study explores such potential influence by investigating the effect of cognitive reserve (a latent construct using education and occupation) and physical, psychological, and social determinants on cognitive function in community dwelling elderly.

Methods

A community-based cross-sectional study was conducted in urban areas of West Bengal (India) among elderly aged ≥60 years. Data was collected by personal interviews for socio-demographic and medical profile. Cognitive function was assessed using Bangla Adaptation of Mini-Mental State Examination (BAMSE). Educational level and occupational complexity were used as proxy indicators for calculating cognitive reserve.

Results

Of the 370 elderlies interviewed (mean age = 68.9 years), cognitive function was abnormal in 13.5%. The cognitive function had a significant inverse relationship with depression symptoms, loneliness, hypertension, anemia, and basic activities of daily living. There was a significant difference in the cognitive reserve of the elderly with normal and abnormal cognitive function (mean 33.7 and 26.8, respectively). In the presence of covariates like sleep quality, depression, hypertension, and hemoglobin levels, the effect of age on cognitive function had a significant mediation influence of cognitive reserve - total effect = -0.2349; 95% CI = (-0.2972 to -0.1725) and direct effect = -0.2583; 95% CI = (-0.3172 to -0.1994).

Conclusion

The quantum of effect of the age on cognitive function decreases with good cognitive reserve as a cognitive reserve has a significant mediation effect on the relationship between age and cognitive function.

The role of social and intellectual activity participation in older adults' cognitive function

THEORETICAL BACKGROUND

A challenge of the ageing of the population is cognitive performance, given its association to optimal ageing. Documented predictors of cognition have included socio-demographics, education or physical factors. However, the association of social and intellectual activity participation to cognition has been less studied.

AIM

This study presents a predictive model of cognitive functioning including these alternative factors as well as more seminal ones to explain cognition in old age.

MATERIALS AND METHODS

The sample was composed by 45475 older adult participants in the 8th Wave of the Survey of Health, Aging and Retirement in Europe, that took place between 2019 and 2020. A correlational design was specified to test the effects of age, gender, years of education, physical inactivity, number of chronic diseases, social activity participation and intellectual activity participation on temporal orientation, numeracy, verbal fluency and memory. A completely a priori Structural Equation Model with latent variables was tested.

RESULTS

The sample had an average of 70 years of age, was well-educated and physically active and engaged in reading. There was a higher proportion of females. The model showed an optimal fit to the data, explaining 8.7%-36.0% of the different cognitive components' variance. Age, years of education and intellectual activity displayed the largest effects across the cognitive domains.

CONCLUSIONS

Findings suggest that social and intellectual activity participation are of relative importance to predict cognition in old age, even when considering other well-documented factors affecting older adults' cognitive functioning.

Life-course socioeconomic conditions and cognitive performance in older adults: a cross-cohort comparison

OBJECTIVES

Socioeconomic disadvantage predicts the level of cognitive performance in old age, but findings have been mixed for trajectories of performance. This study examined associations between life-course socioeconomic conditions, including social mobility, and cognitive performance assessed in terms of level and change, across multiple cognitive domains in two independent cohorts of older adults.

METHODS

Data were from two Swiss population-based cohorts: CoLaus|PsyCoLaus (N = 1210, mean age 72 years) and Vivre/Leben/Vivere (N = 993, mean age 75 years). Verbal fluency, processing speed, cognitive flexibility, memory, and global cognitive performance were assessed at two time points, each spaced 6 years apart. Associations between socioeconomic conditions (father's occupation, parental education, own education, own occupation, household income, and social mobility) and cognitive performance were examined within each cohort, and using pooled data. Covariates included health behaviors, comorbidities, and depressive symptoms.

RESULTS

Across cohorts, socioeconomic disadvantage predicted a lower level of performance across different cognitive domains, including processing speed, verbal fluency, and memory. Moreover, individuals who experienced life-course socioeconomic disadvantage performed worse than those who experienced upward social mobility. Associations between socioeconomic disadvantage and cognitive decline were less consistent.

CONCLUSION

Life-course socioeconomic conditions predict performance level across different cognitive domains, and, to a lesser extent, performance trajectories.

Association of Education and Intracranial Volume With Cognitive Trajectories and Mortality Rates Across the Alzheimer Disease Continuum

Objective

To investigate relationships of education and intracranial volume (ICV) (factors related to cognitive and brain reserve, respectively) with cognitive trajectories and mortality in individuals with biomarker-defined Alzheimer disease (AD).

Methods

We selected 1,298 β-amyloid–positive memory clinic patients with subjective cognitive decline (SCD, n = 142), mild cognitive impairment (MCI, n = 274), or AD dementia (n = 882) from the Amsterdam Dementia Cohort. All participants underwent baseline MRI and neuropsychological assessment, and 68% received cognitive follow-up (median 2.3 years, interquartile range 2.4). Mortality data were collected from the Central Public Administration. In the total sample and stratified by disease stage (i.e., SCD/MCI vs dementia), we examined education and ICV as predictors of baseline and longitudinal cognitive performance on 5 cognitive domains (memory, attention, executive, language, and visuospatial functions; linear mixed models) and time to death (Cox proportional hazard models). Analyses were adjusted for age, sex, whole brain gray matter atrophy, and MRI field strength.

Results

Education and ICV showed consistent positive associations with baseline cognition across disease stages. Longitudinally, we observed a relationship between higher education and faster cognitive decline among patients with dementia on global cognition, memory, executive function, and language (range β = −0.06 to −0.13; all p < 0.05). Furthermore, in the total sample, both higher education and larger ICV were related to lower mortality risk (hazard ratio 0.84 and 0.82, respectively; p < 0.05).

Discussion

In this β-amyloid–positive memory clinic sample, both cognitive and brain reserve were positively associated with baseline cognition, whereas only education was related to longitudinal cognition (i.e., accelerated decline among more highly educated patients with dementia). Higher education and ICV both moderately attenuated overall mortality risk in AD.

Coordinated data analysis: Knowledge accumulation in lifespan developmental psychology

Coordinated analysis is a powerful form of integrative analysis, and is well suited in its capacity to promote cumulative scientific knowledge, particularly in subfields of psychology that focus on the processes of lifespan development and aging. Coordinated analysis uses raw data from individual studies to create similar hypothesis tests for a given research question across multiple datasets, thereby making it less vulnerable to common criticisms of meta-analysis such as file drawer effects or publication bias. Coordinated analysis can sometimes use random effects meta-analysis to summarize results, which does not assume a single true effect size for a given statistical test. By fitting parallel models in separate datasets, coordinated analysis preserves the heterogeneity among studies, and provides a window into the generalizability and external validity of a set of results. The current article achieves three goals: First, it describes the phases of a coordinated analysis so that interested researchers can more easily adopt these methods in their labs. Second, it discusses the importance of coordinated analysis within the context of the credibility revolution in psychology. Third, it encourages the use of existing data networks and repositories for conducting coordinated analysis, in order to enhance accessibility and inclusivity. Subfields of research that require time- or resource- intensive data collection, such as longitudinal aging research, would benefit by adopting these methods. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The Neurocognitive Study for the Aging: Longitudinal Analysis on the Contribution of Sex, Age, Education and APOE ɛ4 on Cognitive Performance

Objective: The effects of normal cognitive aging on executive functions (EF), Verbal Episodic Memory (VEM) and the contribution of age, sex, education, and APOΕ ε4 in a group of old Greek Cypriots across a five-year period were investigated. Design: NEUROAGE, the first project on cognitive aging in Cyprus, is a prospective longitudinal study with a rolling admission process. Participants are assessed at baseline and retested every 24-30 months. Subjects: 170 participants completed all three testing cycles; 86 men and 84 women with ages ranging between 60 and 88 years (mean = 73.21, SD = 5.84); education, 2-20 years (mean = 9.07, SD = 4.27). Results: Α Repeated Measures Multivariate Analysis of Covariance was conducted with one between-subject factor: sex; two covariates: age and education, while Time (time 1, time 2, time 3) served as a within - subject factor. Time did not have an effect on mini mental status examination in Greek (MMSE), EF or VEM. Also, sex had no effect on MMSE, EF and VEM. There was no time by sex interaction. Age and Education significantly predicted the EF performance, F(1, 168) = 11.23, p < 0.05; F(1, 158) = 90.03, p < 0.001 and VEM performance, F(1, 171) = 17.22, p < 0.001; F(1, 171) = 61.25, p < 0.001. Furthermore, there was a significant interaction effect between time and education, for EF, F(2, 167) = 7.02, p < 0.001. Performance of the APOE ε4 carriers did not differ on any of the above measures as compared to performance of non-carriers in this older adult group. Conclusion: Cognitively healthy adults maintained overall cognitive performance across the five-year period. Male and female participants performed similarly and the pattern of change over time was similar across the two sexes. Education was predictive of VEM and EF performance across time. Furthermore, those with higher education maintained higher levels of EF performance. APOE results did not differentiate performance at baseline. Implications of findings are discussed.

Increasingly capable at the ripe old age? Cognitive abilities from 2004 to 2013 in Germany, Spain, and Sweden

Background

Life expectancy is increasing in most high-income countries, but gains in life years are maximized if spent in good health and if cognitive abilities are maintained until old age. Age-related decline of cognitive abilities does nevertheless occur, but the pace of decline is decisive. This was the starting point for our study that aims to examine cohort effects of cognitive aging in women and men in Germany, Spain and Sweden by analyzing changes from 2004 to 2013 by estimating cohort effects within age groups starting from the age of 50 years.

Methods

A cohort study was conducted that was based on data of the surveys 2004 (N = 6,081) and 2013 (N = 8,650) from the Survey of Health, Ageing and Retirement in Europe (SHARE). The analyses were based on data of female and male respondents aged 50 years and older. Age-specific means of verbal fluency and delayed recall from the German, Spanish and Swedish samples were the cognitive domains considered in the study.

Results

In both domains of cognitive ability the achievements in the later surveys were higher than in the earlier ones. This was found in all countries, abut achievement levels increased markedly in the German and the Spanish samples, while the scores of the Swedish samples were not significantly different.

While the highest scores were found for Sweden, Germany ranked in the middle and the lowest scores were found in the Spanish samples. Over time, the scores of the German samples approached those of Sweden.

Conclusions

From the first to the second survey, improvements of older adults’ cognitive abilities were found for all countries considered. This may indicate improvements of the underlying educational systems, but also increasingly stimulating general living conditions.

Duration of subjective poverty in relation to subsequent cognitive performance and decline among adults aged ≥64 in China, 2005-2018

BACKGROUND

The effects of late-life subjective poverty on brain health are understudied. We aimed to investigate the association between duration of subjective poverty after age 64 and subsequent cognitive function and decline in China.

METHODS

Data were from 4118 adults aged ≥64 at baseline in the population-based China Longitudinal Healthy Longevity Survey (CLHLS), 2005-2018. The duration of subjective poverty was measured from self-rated economic status relative to neighbors in 2005, 2008, and 2011 (never; one time point; two or three time points). Cognitive function was assessed by the Chinese Mini-Mental State Exam (CMMSE; range: 0-30) in 2011, 2014, and 2018. We fitted attrition-weighted, multivariable mixed-effects Tobit regression models to examine the relationship between duration of subjective poverty from 2005 to 2011 and subsequent cognitive function and decline from 2011 to 2018.

RESULTS

A total of 2675 (64.96%) participants never reported subjective poverty over the period 2005-2011, 930 (22.58%) participants reported subjective poverty at one time point, and 513 (12.46%) reported subjective poverty at two or three time points. Compared to those who never reported subjective poverty, participants experiencing subjective poverty at one time point (β = -0.95, 95% CI: -1.48 to -0.41) and two or three time points (β = -2.01; 95% CI: -2.73 to -1.29) had lower CMMSE scores in 2011, indicating a dose-response relationship. Individuals with a longer duration of subjective poverty had a slower rate of decline in CMMSE scores than those never in subjective poverty (β = 1.44; 95% CI: 0.20 to 2.68 for 2018 X Two or three time points).

CONCLUSION

Subjective poverty in late life may have unique and cumulative contributions to cognitive aging among older adults in China. The lower level of initial cognitive function but slower rate of cognitive decline observed for those with greater subjective poverty is consistent with theories of cognitive reserve and empirical evidence from Western settings on other socioeconomic markers.

Cross-national Differences in the Association Between Retirement and Memory Decline

OBJECTIVE

Retirement is a potential trigger for cognitive aging as it may be a stressful life event accompanied by changes in everyday activities. However, the consequences of retirement may differ across institutional contexts which shape retirement options. Comparing memory trajectories before and after retirement in 17 European countries, this study aims to identify cross-national differences in the association between retirement and memory decline.

METHOD

Respondents to the longitudinal Survey of Health, Aging, and Retirement in Europe (SHARE; N = 8,646) aged 50+ who were in paid work at baseline and retired during the observation period completed up to 6 memory assessments (immediate and delayed word recall) over 13 years. Three-level (time points, individuals, and countries) linear mixed models with country-level random slopes for retirement were estimated to evaluate whether memory decline accelerated after retirement and if this association differed between countries.

RESULTS

On average, retirement was associated with a moderate decrement in word recall (b = -0.273, 95% CI -0.441, -0.104) and memory decline accelerated after retirement (b = -0.044, 95% CI -0.070, -0.018). Significant between-country heterogeneity in memory decline after retirement existed (variance = 0.047, 95% CI (0.013, 0.168). Memory decline after retirement was more rapid in Italy, Greece, Czech Republic, Poland, Portugal, and Estonia compared to Northern and Central European countries.

DISCUSSION

Memory decline postretirement was faster in Mediterranean and eastern European countries, which are characterized by less generous welfare systems with comparatively low pension benefits. Evaluation of resources that could protect retirees from memory decline would be valuable.

Education and Cognitive Functioning Across the Life Span

Cognitive abilities are important predictors of educational and occupational performance, socioeconomic attainment, health, and longevity. Declines in cognitive abilities are linked to impairments in older adults' everyday functions, but people differ from one another in their rates of cognitive decline over the course of adulthood and old age. Hence, identifying factors that protect against compromised late-life cognition is of great societal interest. The number of years of formal education completed by individuals is positively correlated with their cognitive function throughout adulthood and predicts lower risk of dementia late in life. These observations have led to the propositions that prolonging education might (a) affect cognitive ability and (b) attenuate aging-associated declines in cognition. We evaluate these propositions by reviewing the literature on educational attainment and cognitive aging, including recent analyses of data harmonized across multiple longitudinal cohort studies and related meta-analyses. In line with the first proposition, the evidence indicates that educational attainment has positive effects on cognitive function. We also find evidence that cognitive abilities are associated with selection into longer durations of education and that there are common factors (e.g., parental socioeconomic resources) that affect both educational attainment and cognitive development. There is likely reciprocal interplay among these factors, and among cognitive abilities, during development. Education-cognitive ability associations are apparent across the entire adult life span and across the full range of education levels, including (to some degree) tertiary education. However, contrary to the second proposition, we find that associations between education and aging-associated cognitive declines are negligible and that a threshold model of dementia can account for the association between educational attainment and late-life dementia risk. We conclude that educational attainment exerts its influences on late-life cognitive function primarily by contributing to individual differences in cognitive skills that emerge in early adulthood but persist into older age. We also note that the widespread absence of educational influences on rates of cognitive decline puts constraints on theoretical notions of cognitive aging, such as the concepts of cognitive reserve and brain maintenance. Improving the conditions that shape development during the first decades of life carries great potential for improving cognitive ability in early adulthood and for reducing public-health burdens related to cognitive aging and dementia.

The mechanisms of the protective effect of education in cognitive aging

Frequent cases of pathological brain aging are an important scientific and social problem. Some people have the ability to compensate for the initial manifestations of pathological aging and delay the development of the clinical phenomena of the disease. The concept of “cognitive reserve” allows us to study the possibilities of increasing brain stability in conditions of pathological aging. The identification of the dominant form of thinking, converging or diverging, reveals possible neurophysiological mechanisms of the cognitive reserve. Understanding the mechanisms of formation of individual cognitive styles actualizes the contribution of the “Education” factor to the development of the cognitive reserve. The research material was scientific publications on the topic of work. It was revealed that the “education” factor can realize its protective effect on the pathological aging of the brain due to the formation of an adaptive form of thinking. The data presented in this review make it possible to substantiate the medical and social significance of educational programs for people of mature and older age.

[Socioeconomic inequalities in health among the elderly population in Spain]

OBJECTIVE

To examine socioeconomic inequalities in health in the older population in Spain.

METHOD

A systematic search and review of the literature published between 2000 and 2017 in English and Spanish was conducted in Social Science Citation Index, Sociology Database, Scopus, PubMed and Embase. Primary and secondary studies analysing these inequalities in Spain were included. Two researchers were responsible for the selection of the studies and the extraction of the information (first author, year of publication, region, design, population/sample, socioeconomic and health indicators used, and main results).

RESULTS

A total of 89 articles were included, corresponding to 87 studies. Of the studies, 81.6% were cross-sectional, 88.5% included only non-institutionalised population and 35.6% were carried out at a national level. The studies analysed social inequalities in the following health indicators: functional status (n=29), morbidity (n=19), self-perceived health (n=18), mental and emotional health (n=10), cognitive status (n=7), quality of life (n=9), mortality (n=15) and life expectancy (n=2). Socioeconomic inequalities were detected in all of them, although the magnitude varied depending on the socioeconomic and health indicator used. The educational level and the ecological indexes were the indicators that detected more inequalities in health. The impact of inequalities by sex was different in functional status, morbidity, self-perceived health, mental and emotional health and mortality.

CONCLUSION

There are socioeconomic inequalities in health among the elderly population and their magnitude varies by sex in some of the health indicators. The increase in educational level and the maintenance of sufficient pensions can be key policies that contribute to the reduction of inequalities in this population group.

Education and age-related decline in cognitive performance: Systematic review and meta-analysis of longitudinal cohort studies

Central theories of cognitive aging propose that education is an important protective factor for decline in cognitive performance in older age. We conducted a systematic review and meta-analysis of reported estimates of an association between educational attainment and change in performance in six cognitive domains (episodic memory, processing speed, verbal fluency, crystallized intelligence, fluid intelligence, and global ability) in the general population of older individuals. The systematic search (11^th of October 2019) identified 92 eligible articles. The episodic memory domain had the highest number of estimates (37 estimates from 18 articles, n = 109,281) included in the meta-analysis. The fewest estimates (6 estimates from 6 articles, n = 5263) were included for fluid intelligence. Pooled mean estimates from an inverse-variance weighted random effects analysis were not statistically significant and indicated that any association between education and change in cognitive performance is likely of a negligible magnitude. The estimates for education's role (one additional year) for change in cognitive performance ranged from -0.019 (95 % confidence interval, CI = -0.047, 0.010) to 0.004SD (CI = -0.003, 0.012) per decade. Even if the larger positive point estimates (i.e., protective effects) are selectively considered, the influence of education on change is still at least 12 times less important for the cognitive functioning of an older individual than the association between education and level of cognitive performance. Sensitivity analyses did not substantially alter these results. However, heterogeneity was substantial, and remained largely unexplained by mean age, mean educational attainment, Gini coefficient, GDP per capita, maximum follow-up period, and publication year. Overall, education is an important factor in aging due to its robust association with level of performance, but the current base of empirical evidence is not revealing a consistent and substantial association between educational attainment and changes in cognitive performance in the general population. Theories of cognitive aging must be updated to incorporate this pattern of findings.

Differences in cognitive performance and cognitive decline across European regions: a population-based prospective cohort study

BACKGROUND

A large variation in cognitive performance exists between European regions. However, it is unclear how older Europeans differ in the rate of cognitive decline.

METHODS

We analysed data from 22 181 individuals (54% women; median age 71) who participated in the Survey on Health, Ageing and Retirement in Europe. Cognition was measured using tests on verbal fluency, immediate and delayed recall. We used linear regression and linear mixed effects regression to examine regional differences in the level of cognitive performance and the rate of cognitive decline.

RESULTS

Scandinavians had the highest baseline cognitive scores (mean standardized overall cognitive score 0.3), followed by Western Europeans (mean 0.2), Central and Eastern Europeans (mean 0.1) and individuals from Mediterranean countries (mean -0.4). These differences persisted even after adjustment for sociodemographic and clinical characteristics. The annual cognitive decline in Scandinavia (0.59%) was approximately two times greater than in Western Europe (0.28%), Central and Eastern Europe (0.25%) and Mediterranean countries (0.23%).

DISCUSSION

There are substantial differences in cognitive performance as well as rates of cognitive decline among the elderly throughout European regions. This might be explained by differing levels of cognitive reserve.

[Social inequalities in health among the elderly population: review of indicators used in Spain]

OBJECTIVE

To identify the indicators of social position used to evaluate inequalities in health among the population aged 65 and over in Spain.

METHOD

A systematic search of the literature published in English and Spanish since 2000 in health and social databases was carried out. Primary and secondary studies analyzing these inequalities in Spain were included. The indicators used were identified, as well as the advantages and limitations pointed out by the authors. The main findings were synthesized in a review of the literature.

RESULTS

We included 87 studies, described in 89 articles. The socioeconomic indicators employed were both individual and ecological. Among the former, educational level was the most analyzed socioeconomic variable (n=73). Other individual variables used were occupation (n=17), objective economic level (n=16), subjective economic level (n=4), housing and household material wealth (n=6), relationship with work activity (n=5), and mixed measures (n=5). Among the ecological indicators, simple (n=3) and complex indices (n=7) were identified. The latter had been constructed based on several indicators, such as educational level and unemployment. Inequalities in multiple health indicators were analyzed, self-perceived health being the only indicator assessed according to all the socioeconomic indicators described.

CONCLUSIONS

A wide variety of indicators is identified for the evaluation of social inequalities in health among the elderly population. There have not been sufficiently assessed from a gender perspective; this is a line of interest for future research.

Defining Cognitive Reserve and Implications for Cognitive Aging

PURPOSE OF REVIEW

The aim of this review is to summarize current conceptual models of cognitive reserve (CR) and related concepts and to discuss evidence for these concepts within the context of aging and Alzheimer's disease.

RECENT FINDINGS

Evidence to date supports the notion that higher levels of CR, as measured by proxy variables reflective of lifetime experiences, are associated with better cognitive performance, and with a reduced risk of incident mild cognitive impairment/dementia. However, the impact of CR on longitudinal cognitive trajectories is unclear and may be influenced by a number of factors. Although there is promising evidence that some proxy measures of CR may influence structural brain measures, more research is needed. The protective effects of CR may provide an important mechanism for preserving cognitive function and cognitive well-being with age, in part because it can be enhanced throughout the lifespan. However, more research on the mechanisms by which CR is protective is needed.

Non-professional caregiver burden is associated with the severity of patients' cognitive impairment

Background/Objectives

To analyse the relationship between caregiver burden and severity of patients’ cognitive impairment.

Design

Data were drawn from the cross-sectional 2015/2016 Adelphi Real World Dementia Disease-Specific Programme.

Setting

This research was multi-national and studied physicians and their consulting patients with cognitive impairment.

Participants

1,201 caregivers completed self-assessment forms.

Measurements

Validated instruments of caregiver wellbeing and burden (EQ-5D-3L questionnaire, EQ-VAS, Zarit Burden Interview, and Work Productivity and Activity Impairment questionnaire) and number of caregiver hours were analysed by severity of patients’ cognitive impairment, categorised according to the Mini-Mental State Examination. Data were analysed using Spearman’s rank correlation coefficients and ordinary least squares regression models, to compare outcomes between caregivers of patients with prodromal, mild, moderate, and severe dementia.

Results

The majority of caregivers were female (69.1%), lived with the patient they cared for (75.8%), and only approximately one third (28.3%) were in part- or full-time employment. There were statistically significant (p<0.001) increases in caregiver time (36.9 versus 108.6 hours per week for prodromal versus severe dementia, respectively) and measures of caregiver burden and health status (EQ-5D-3L, EQ-VAS, and Zarit Burden Interview) and increases in measures of work productivity and activity impairment with increasing severity of patients’ disease.

Conclusion

This study of real-world data confirmed an association between increased caregiver burden and severity of patients’ cognitive impairment by analysis of a wide range of validated measures of caregiver burden. These findings suggest that maintaining patients in the earliest stages of their disease for as long as possible may potentially help to protect caregiver wellbeing, although further research is required to confirm this hypothesis.

Cognitive Function and Impairment in Older, Rural South African Adults: Evidence from "Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in Rural South Africa"

BACKGROUND/AIMS

We aimed to estimate the prevalence of cognitive impairment, and the sociodemographic and comorbid predictors of cognitive function among older, rural South African adults.

METHODS

Data were from a population-based study of 5,059 adults aged ≥40 years in rural South Africa in 2015. Cognitive impairment was defined as scoring ≤1.5 SDs below the mean composite time orientation and memory score, or requiring a proxy interview with "fair" or "poor" proxy-reported memory. Multiple linear regression estimated the sociodemographic and comorbid predictors of cognitive score, with multiplicative statistical interactions between each of age and sex with education.

RESULTS

Cognitive impairment increased with age, from 2% of those aged 40-44 (11/516) to 24% of those aged ≥75 years (214/899). The independent predictors of lower cognitive score were being older, female, unmarried, not working, having low education, low household wealth, and a history of cardiovascular conditions. Education modified the negative associations between female sex, older age, and cognitive function score.

CONCLUSIONS

The prevalence of cognitive impairment increased with age and is comparable to rates of dementia reported in other sub-Saharan African countries. Age and sex differences in cognitive function scores were minimized as education increased, potentially reflecting the power of even poor-quality education to improve cognitive reserve.

Impacts of cognitive impairment for different levels and causes of traumatic brain injury, and education status in TBI patients

Traumatic brain injury (TBI) is one of main causes of death and disability among many young and old populations in different countries.

OBJECTIVE

The aim of this study were to consider and predict the cognitive impairments according to different levels and causes of TBI, and education status.

METHODS

The study was performed using the Mini-Mental State Examination (MMSE) to estimate cognitive impairment in patients at a trauma center in Zahedan city. Individuals were considered eligible if 18 years of age or older. This investigation assessed a subset of patients from a 6-month pilot study.

RESULTS

The study participants comprised 66% males and 34% females. Patient mean age was 32.5 years and SD was 12.924 years. One-way analysis of variance between groups indicated cognitive impairment related to different levels and causes of TBI, and education status in patients. There was a significant difference in the dimensions of cognitive impairments for different levels and causes of TBI, and education status. A regression test showed that levels of traumatic brain injury (b=.615, p=.001) and education status (b=.426, p=.001) predicted cognitive impairment.

CONCLUSION

Different levels of TBI and education status were useful for predicting cognitive impairment in patients. Severe TBI and no education were associated with worse cognitive performance and higher disability. These data are essential in terms of helping patients understand their needs. Therefore, the factors identified can help plan effective rehabilitation programs.

The Relationship between Cognitive Reserve and Math Abilities

Cognitive Reserve is the capital of knowledge and experiences that an individual acquires over their life-span. Cognitive Reserve is strictly related to Brain Reserve, which is the ability of the brain to cope with damage. These two concepts could explain many phenomena such as the modality of onset in dementia or the different degree of impairment in cognitive abilities in aging. The aim of this study is to verify the effect of Cognitive Reserve, as measured by a questionnaire, on a variety of numerical abilities (number comprehension, reading and writing numbers, rules and principles, mental calculations and written calculations), in a group of healthy older people (aged 65–98 years). Sixty older individuals were interviewed with the Cognitive Reserve Index questionnaire (CRIq), and assessed with the Numerical Activities of Daily Living battery (NADL), which included formal tasks on math abilities, an informal test on math, one interview with the participant, and one interview with a relative on the perceived math abilities. We also took into account the years of education, as another proxy for Cognitive Reserve. In the multiple regression analyses on all formal tests, CRIq scores did not significantly predict math performance. Other variables, i.e., years of education and Mini-Mental State Examination score, accounted better for math performance on NADL. Only a subsection of CRIq, CRIq-Working-activity, was found to predict performance on a NADL subtest assessing informal use of math in daily life. These results show that education might better explain abstract math functions in late life than other aspects related to Cognitive Reserve, such as lifestyle or occupational attainment.

Decline in Search Speed and Verbal Memory Over 26 Years of Midlife in a British Birth Cohort

BACKGROUND

Cognitive capabilities change in later life, although their onset and rate of decline, and how they are shaped by lifetime socioeconomic position, childhood cognition and adult health status are all unclear.

METHODS

From the Medical Research Council National Survey of Health and Development, we analysed 3,192 participants undergoing one or more cognitive assessments at ages 43, 53, 60-64 and 69. Linear mixed models described cognitive trajectories, adjusting for factors across the life course.

RESULTS

For both search speed and verbal memory, better performance at age 43 (the intercept) was associated with higher paternal and own education, childhood cognition, and adult occupational class. For search speed, the trajectory was best described as a quadratic function (decline of 45.6 letters/5-years + 4.6 letters). Verbal memory showed a linear decline of 0.20 words/5-years between ages 43 and 60 and a steeper linear decline of 0.95 words/5-years between ages 60 and 69. Decline in verbal memory in the latter period was steeper in those with higher educational achievements at age 26 (additional 0.28 words/5-years for highest attainment).

CONCLUSIONS

Decline in verbal memory and search speed across midlife is evident, though with different non-linear trajectories. By implication, pathways to cognitive impairment and dementia in older age may have their origins in this period.