Effects of education and race on cognitive decline: An integrative study of generalizability versus study-specific results

Inequalities in accelerated cognitive decline: Resolving observational window bias using nested non-linear regression

INTRODUCTION

Limited observational windows lead to conflicting results in studies examining educational differences in Alzheimer's disease and related dementias (ADRD) risk, due to observational window bias relative to onset of accelerated cognitive decline. This study tested a novel model to address observational window bias and tested for the presence and sources of disparities in accelerated cognitive declines due to ADRD.

METHODS

The sample examined 167,314 cognitive assessments from 32,441 Health and Retirement Study participants. We implemented a parametric non-linear nested longitudinal regression and reported multivariable-adjusted nodal incidence ratios (aNIR).

RESULTS

University degrees were associated with lower incidence (aNIR = 0.253, 95% confidence interval [CI] = [0.221 to 0.289], p < 0.001), while black participants had a higher incidence (aNIR = 1.995, [1.858 to 2.141], p < 0.001) of accelerated cognitive decline, adjusting for demographic, sociobehavioral, and medical risk factors. Sex-stratified analyses identified diminished educational returns for women and increased incidence among minoritized women.

DISCUSSION

Addressing observational window bias reveals large social inequalities in the onset of accelerated cognitive declines indicative of ADRD.

HIGHLIGHTS

This study identifies observational window bias as a source of conflicting results among previous studies of educational achievement in Alzheimer's disease and related dementias (ADRD) disparities. The study locates preclinical accelerated cognitive decline, which is indicative of ADRD while occurring 10+ years prior to symptom onset, as a site to study ADRD disparities that mitigates observational window bias. A novel method, nested non-linear regression, is developed to test for differences in the onset of accelerated cognitive decline. Educational and racial/ethnic disparities are demonstrated in the onset of accelerated cognitive decline, as are their intersecting differences with sex/gender.

Social determinants of health but not global genetic ancestry predict dementia prevalence in Latin America

INTRODUCTION

Leveraging the nonmonolithic structure of Latin America, which represents a large variability in social determinants of health (SDoH) and high levels of genetic admixture, we aim to evaluate the relative contributions of SDoH and genetic ancestry in predicting dementia prevalence in Latin American populations.

METHODS

Community-dwelling participants aged 65 and older (N = 3808) from Cuba, Dominican Republic, Mexico, and Peru completed the 10/66 protocol assessments. Dementia was diagnosed using the cross-culturally validated 10/66 algorithm. Multivariate linear regression models adjusted for SDoH were used in the main analysis. This study used cross-sectional data from the 1066 population-based study.

RESULTS

Individuals with higher proportions of Native American (>70%) and African American (>70%) ancestry were more likely to exhibit factors contributing to worse SDoH, such as lower educational levels (p < 0.001), lower socioeconomic status (p < 0.001), and higher frequency of vascular risk factors (p < 0.001). After adjusting for measures of SDoH, there was no association between ancestry proportion and dementia probability, and ancestry proportions no longer significantly accounted for the variance in cognitive performance (African predominant p = 0.31 [-0.19, 0.59] and Native predominant p = 0.74 [-0.24, 0.33]).

DISCUSSION

The findings suggest that social and environmental factors play a more crucial role than genetic ancestry in predicting dementia prevalence in Latin American populations. This underscores the need for public health strategies and policies that address these social determinants to effectively reduce dementia risk in these communities.

HIGHLIGHTS

Countries in Latin America express a large variability in social determinants of health and levels of admixture. After adjustment for downstream societal factors linked to SDoH, genetic ancestry shows no link to dementia. Population ancestry profiles alone do not influence cognitive performance. SDoH are key drivers of racial disparities in dementia and cognitive performance.

Development and validation of the Michigan Chronic Disease Simulation Model (MICROSIM)

Strategies to prevent or delay Alzheimer's disease and related dementias (AD/ADRD) are urgently needed, and blood pressure (BP) management is a promising strategy. Yet the effects of different BP control strategies across the life course on AD/ADRD are unknown. Randomized trials may be infeasible due to prolonged follow-up and large sample sizes. Simulation analysis is a practical approach to estimating these effects using the best available existing data. However, existing simulation frameworks cannot estimate the effects of BP control on both dementia and cardiovascular disease. This manuscript describes the design principles, implementation details, and population-level validation of a novel population-health microsimulation framework, the MIchigan ChROnic Disease SIMulation (MICROSIM), for The Effect of Lower Blood Pressure over the Life Course on Late-life Cognition in Blacks, Hispanics, and Whites (BP-COG) study of the effect of BP levels over the life course on dementia and cardiovascular disease. MICROSIM is an agent-based Monte Carlo simulation designed using computer programming best practices. MICROSIM estimates annual vascular risk factor levels and transition probabilities in all-cause dementia, stroke, myocardial infarction, and mortality in a nationally representative sample of US adults 18+ using the National Health and Nutrition Examination Survey (NHANES). MICROSIM models changes in risk factors over time, cognition and dementia using changes from a pooled dataset of individual participant data from 6 US prospective cardiovascular cohort studies. Cardiovascular risks were estimated using a widely used risk model and BP treatment effects were derived from meta-analyses of randomized trials. MICROSIM is an extensible, open-source framework designed to estimate the population-level impact of different BP management strategies and reproduces US population-level estimates of BP and other vascular risk factors levels, their change over time, and incident all-cause dementia, stroke, myocardial infarction, and mortality.

Visual memory and alcohol use in a middle-aged birth cohort

Light and moderate alcohol use has been reported to be associated with both impaired and enhanced cognition. The purpose of this study was to explore whether there was a linear relationship between visual memory and alcohol consumption in males and females in a large middle-aged birth cohort population in cross-sectional and longitudinal settings. Data were collected from 5585 participants completing 31-year (1997-1998) and 46-year (2012-2014) follow-ups including Paired Associate Learning (PAL) test at 46-years follow-up. The participants were originally from 12,231 study population of the Northern Finland Birth Cohort 1966 (NFBC1966). The PAL test was conducted to assess visual memory. Reported alcohol use was measured as total daily use of alcohol, beer, wine, and spirits converted into grams and as frequency and amount of use of beer, wine, and spirits. The total daily alcohol use was not associated with reduced visual memory. The frequency of use of beer and wine in males was associated with better visual memory in cross-sectional and longitudinal settings. Using six or more servings of spirits was associated with worse visual memory in males in cross-sectional and longitudinal settings. Using six or more servings of spirits was associated with worse visual memory in males in cross-sectional and longitudinal setting. The study suggested a lack of a linear association between drinking and visual memory in the middle-aged population.

Unhealthy white matter connectivity, cognition, and racialization in older adults

INTRODUCTION

White matter hyperintensities (WMH) may promote clinical Alzheimer's disease (AD) disparities between Black American (BA) and non-Hispanic White (nHW) populations. Using a novel measurement, unhealthy white matter connectivity (UWMC), we interrogated racialized group differences in associations between WMH in AD pathology-affected regions and cognition.

METHODS

UWMC is the proportion of white matter fibers that pass through WMH for every pair of brain regions. Individual regression models tested associations of UWMC in beta-amyloid (Aβ) or tau pathology-affected regions with cognition overall, stratified by racialized group, and with a racialized group interaction.

RESULTS

In 201 older adults ranging from cognitively unimpaired to AD, BA participants exhibited greater UWMC and worse cognition than nHW participants. UWMC was negatively associated with cognition in 17 and 5 Aβ- and tau-affected regions, respectively. Racialization did not modify these relationships.

DISCUSSION

Differential UWMC burden, not differential UWMC-and-cognition associations, may drive clinical AD disparities between racialized groups.

HIGHLIGHTS

Unhealthy white matter connectivity (UWMC) in Alzheimer's disease (AD) pathology-affected brain regions is associated with cognition. Relationships between UWMC and cognition are similar between Black American (BA) and non-Hispanic White (nHW) individuals. More UWMC may partially drive higher clinical AD burden in BA versus nHW populations. UWMC risk factors, particularly social and environmental, should be identified.

Epigenetic age and socioeconomic status contribute to racial disparities in cognitive and functional aging between Black and White older Americans

Epigenetic age, a biological aging marker measured by DNA methylation, is a potential mechanism by which social factors drive disparities in age-related health. Epigenetic age gap is the residual between epigenetic age measures and chronological age. Previous studies showed associations between epigenetic age gap and age-related outcomes including cognitive capacity and performance on some functional measures, but whether epigenetic age gap contributes to disparities in these outcomes is unknown. We use data from the Health and Retirement Study to examine the role of epigenetic age gap in racial disparities in cognitive and functional outcomes and consider the role of socioeconomic status (SES). Epigenetic age measures are GrimAge or Dunedin Pace of Aging methylation (DPoAm). Cognitive outcomes are cross-sectional score and two-year change in Telephone Interview for Cognitive Status (TICS). Functional outcomes are prevalence and incidence of limitations performing Instrumental Activities of Daily Living (IADLs). We find, relative to White participants, Black participants have lower scores and greater decline in TICS, higher prevalence and incidence rates of IADL limitations, and higher epigenetic age gap. Age- and gender-adjusted analyses reveal that higher GrimAge and DPoAm gap are both associated with worse cognitive and functional outcomes and mediate 6-11% of racial disparities in cognitive outcomes and 19-39% of disparities in functional outcomes. Adjusting for SES attenuates most DPoAm associations and most mediation effects. These results support that epigenetic age gap contributes to racial disparities in cognition and functioning and may be an important mechanism linking social factors to disparities in health outcomes.

Cross-cultural adaptation of assessments for time-related abilities of Indian older adults and evaluation of their reliability and validity

BACKGROUND

Older adults may have difficulties in daily time management due to age-related or disease-related cognitive impairment. Standardised assessments for time-related abilities are currently unavailable in India.

AIM

The study aimed to adapt the Kit for Assessing Time-processing Ability-Senior (KaTid-Senior) and Time-Self rating, Senior (Time-S Senior) for daily time management of Indian older adults, translate these into an Indian language, and evaluate the reliability and validity of the adapted assessments.

MATERIALS AND METHODS

The two Swedish-origin assessments were reviewed, adapted for linguistic and cultural relevance into English, and translated into Kannada language. Older adults (n = 128) were conveniently selected, assessed with the Montreal Cognitive Assessment, and assigned to age and gender-matched groups: cognitively-impaired and cognitively-normal. Data was then collected with the adapted assessments.

RESULTS

Both adapted assessments demonstrated acceptable reliability (internal consistency) in this sample (α =0.89 - 0.90). The cognitively-impaired group had significantly (p < 0.001) lower scores on the assessments as compared to the cognitively-normal group. There was a strong to moderate correlation between the assessments supporting their convergent validity.

CONCLUSIONS

The adapted assessments are reliable and valid in the Indian context.

SIGNIFICANCE

The study would facilitate contextually-relevant assessment and management of time-related abilities in Indian older adults.

Social and Neighborhood Context Moderates the Associations Between Processing Speed and Driving Mobility: A 10-year Analysis of the ACTIVE Study

Objectives: Processing speed is essential to functional independence in later life, such as driving a vehicle. Few studies have examined processing speed and driving mobility in the context of racial differences and social determinants of health (SDoH). This study characterized the longitudinal association between processing speed and driving mobility, and how it varied by race and SDoH. Methods: Using data from the control arm of the Advanced Cognitive Training in Vital Elderly study (n = 581, 24.5% Black), multilevel models examined longitudinal associations between processing speed and driving mobility outcomes (driving space, exposure, and difficulty). Race and SDoH moderations were explored. Results: Decline in processing speed measures was associated with increased self-reported driving difficulty, but only for older adults with below-average to average scores for neighborhood and built environments and social community context SDoH domains. Discussion: Findings emphasize the influence of physical and social environmental characteristics on processing speed and driving mobility.

Retirement and cognitive aging in a racially diverse sample of older Americans

BACKGROUND

Retirement represents a crucial transitional period for many adults with possible consequences for cognitive aging. We examined trajectories of cognitive change before and after retirement in Black and White adults.

METHODS

Longitudinal examination of up to 10 years (mean = 7.1 ± 2.2 years) using data from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study-a national, longitudinal study of Black and White adults ≥45 years of age. Data were from 2226 members of the REGARDS study who retired around the time when an occupational ancillary survey was administered. Cognitive function was an average of z-scores for tests of verbal fluency, memory, and global function.

RESULTS

Cognitive functioning was stable before retirement (Estimate = 0.05, p = 0.322), followed by a significant decline after retirement (Estimate = -0.15, p < 0.001). The decline was particularly pronounced in White (Estimate = -0.19, p < 0.001) compared with Black (Estimate = -0.07, p = 0.077) participants, twice as large in men (Estimate = -0.20, p < 0.001) compared with women (Estimate = -0.11, p < 0.001), highest among White men (Estimate = -0.22, p < 0.001) and lowest in Black women (Estimate = -0.04, p = 0.457). Greater post-retirement cognitive decline was also observed among participants who attended college (Estimate = -0.14, p = 0.016). While greater work complexity (Estimate = 0.92, p < 0.05) and higher income (Estimate = 1.03, p < 0.05) were related to better cognitive function at retirement, neither was significantly related to cognitive change after retirement.

CONCLUSION

Cognitive functioning may decline at an accelerated rate immediately post-retirement, more so in White adults and men than Black adults and women. Lifelong structural inequalities including occupational segregation and other social determinants of cognitive health may obscure the role of retirement in cognitive aging.

Genetics of Alzheimer's Disease in the African American Population

Black/African American (AA) individuals have a higher risk of Alzheimer's disease (AD) than White non-Hispanic persons of European ancestry (EUR) for reasons that may include economic disparities, cardiovascular health, quality of education, and biases in the methods used to diagnose AD. AD is also heritable, and some of the differences in risk may be due to genetics. Many AD-associated variants have been identified by candidate gene studies, genome-wide association studies (GWAS), and genome-sequencing studies. However, most of these studies have been performed using EUR cohorts. In this paper, we review the genetics of AD and AD-related traits in AA individuals. Importantly, studies of genetic risk factors in AA cohorts can elucidate the molecular mechanisms underlying AD risk in AA and other populations. In fact, such studies are essential to enable reliable precision medicine approaches in persons with considerable African ancestry. Furthermore, genetic studies of AA cohorts allow exploration of the ways the impact of genes can vary by ancestry, culture, and economic and environmental disparities. They have yielded important gains in our knowledge of AD genetics, and increasing AA individual representation within genetic studies should remain a priority for inclusive genetic study design.

The impacts of social determinants of health and cardiometabolic factors on cognitive and functional aging in Colombian underserved populations

Global initiatives call for further understanding of the impact of inequity on aging across underserved populations. Previous research in low- and middle-income countries (LMICs) presents limitations in assessing combined sources of inequity and outcomes (i.e., cognition and functionality). In this study, we assessed how social determinants of health (SDH), cardiometabolic factors (CMFs), and other medical/social factors predict cognition and functionality in an aging Colombian population. We ran a cross-sectional study that combined theory- (structural equation models) and data-driven (machine learning) approaches in a population-based study (N = 23,694; M = 69.8 years) to assess the best predictors of cognition and functionality. We found that a combination of SDH and CMF accurately predicted cognition and functionality, although SDH was the stronger predictor. Cognition was predicted with the highest accuracy by SDH, followed by demographics, CMF, and other factors. A combination of SDH, age, CMF, and additional physical/psychological factors were the best predictors of functional status. Results highlight the role of inequity in predicting brain health and advancing solutions to reduce the cognitive and functional decline in LMICs.

Processing speed test: Results from a Japanese normative sample of healthy participants compared with a US normative sample

BACKGROUND

The Processing Speed Test (PST), a validated iPad®-based cognitive screening test for MS, has been applied to the cognitive assessment of Japanese MS patients using US normative data.

METHODS

To develop PST normative data from Japanese healthy volunteers and compare the PST score distribution between Japanese and US healthy volunteers, 254 healthy Japanese-speaking volunteers were enrolled and stratified by age (20-65 years). Potential participants with a Mini-Mental State Examination score < 27 were excluded. PST raw scores (total correct) were from the Japan cohort and compared with age-restricted US normative data and propensity score-matched data created by matching sex, age, and educational level from a published study of 428 healthy participants. PST score distributions and standardized z-scores were compared using t-test and Kolmogorov-Smirnov test statistics.

RESULTS

The mean age of the Japan cohort was 44.1 years. The PST scores of Japanese volunteers were significantly different from those of the age-restricted (mean ± SD 61.8 ± 10.1 vs 53.7 ± 10.8; p < 0.001) and the propensity score-matched US cohort (62.1 ± 10.1 vs 53.3 ± 10.6; p < 0.001).

CONCLUSION

Regression analyses centered on US normative data could underestimate disease severity in Japanese MS patients, suggesting that separate normative data should be considered for each population sample.

Harmonization of Later-Life Cognitive Function Across National Contexts: Results from the Harmonized Cognitive Assessment Protocols (HCAPs)

Background

The Harmonized Cognitive Assessment Protocol (HCAP) is an innovative instrument for cross-national comparisons of later-life cognitive function, yet its suitability across diverse populations is unknown. We aimed to harmonize general and domain-specific cognitive scores from HCAPs across six countries, and evaluate precision and criterion validity of the resulting harmonized scores.

Methods

We statistically harmonized general and domain-specific cognitive function across the six publicly available HCAP partner studies in the United States, England, India, Mexico, China, and South Africa (N=21,141). We used an item banking approach that leveraged common cognitive test items across studies and tests that were unique to studies, as identified by a multidisciplinary expert panel. We generated harmonized factor scores for general and domain- specific cognitive function using serially estimated graded-response item response theory (IRT) models. We evaluated precision of the factor scores using test information plots and criterion validity using age, gender, and educational attainment.

Findings

IRT models of cognitive function in each country fit well. We compared measurement reliability of the harmonized general cognitive function factor across each cohort using test information plots; marginal reliability was high (r> 0·90) for 93% of respondents across six countries. In each country, general cognitive function scores were lower with older ages and higher with greater levels of educational attainment.

Interpretation

We statistically harmonized cognitive function measures across six large, population-based studies of cognitive aging in the US, England, India, Mexico, China, and South Africa. Precision of the estimated scores was excellent. This work provides a foundation for international networks of researchers to make stronger inferences and direct comparisons of cross-national associations of risk factors for cognitive outcomes.

Funding

National Institute on Aging (R01 AG070953, R01 AG030153, R01 AG051125, U01 AG058499; U24 AG065182; R01AG051158).

Associations Between Vascular Risk Factor Levels and Cognitive Decline Among Stroke Survivors

Importance

Incident stroke is associated with accelerated cognitive decline. Whether poststroke vascular risk factor levels are associated with faster cognitive decline is uncertain.

Objective

To evaluate associations of poststroke systolic blood pressure (SBP), glucose, and low-density lipoprotein (LDL) cholesterol levels with cognitive decline.

Design, Setting, and Participants

Individual participant data meta-analysis of 4 US cohort studies (conducted 1971-2019). Linear mixed-effects models estimated changes in cognition after incident stroke. Median (IQR) follow-up was 4.7 (2.6-7.9) years. Analysis began August 2021 and was completed March 2023.

Exposures

Time-dependent cumulative mean poststroke SBP, glucose, and LDL cholesterol levels.

Main Outcomes and Measures

The primary outcome was change in global cognition. Secondary outcomes were change in executive function and memory. Outcomes were standardized as t scores (mean [SD], 50 [10]); a 1-point difference represents a 0.1-SD difference in cognition.

Results

A total of 1120 eligible dementia-free individuals with incident stroke were identified; 982 (87.7%) had available covariate data and 138 (12.3%) were excluded for missing covariate data. Of the 982, 480 (48.9%) were female individuals, and 289 (29.4%) were Black individuals. The median age at incident stroke was 74.6 (IQR, 69.1-79.8; range, 44.1-96.4) years. Cumulative mean poststroke SBP and LDL cholesterol levels were not associated with any cognitive outcome. However, after accounting for cumulative mean poststroke SBP and LDL cholesterol levels, higher cumulative mean poststroke glucose level was associated with faster decline in global cognition (-0.04 points/y faster per each 10-mg/dL increase [95% CI, -0.08 to -0.001 points/y]; P = .046) but not executive function or memory. After restricting to 798 participants with apolipoprotein E4 (APOE4) data and controlling for APOE4 and APOE4 × time, higher cumulative mean poststroke glucose level was associated with a faster decline in global cognition in models without and with adjustment for cumulative mean poststroke SBP and LDL cholesterol levels (-0.05 points/y faster per 10-mg/dL increase [95% CI, -0.09 to -0.01 points/y]; P = .01; -0.07 points/y faster per 10-mg/dL increase [95% CI, -0.11 to -0.03 points/y]; P = .002) but not executive function or memory declines.

Conclusions and Relevance

In this cohort study, higher poststroke glucose levels were associated with faster global cognitive decline. We found no evidence that poststroke LDL cholesterol and SBP levels were associated with cognitive decline.

Design of the think PHRESH longitudinal cohort study: Neighborhood disadvantage, cognitive aging, and alzheimer's disease risk in disinvested, black neighborhoods

BACKGROUND

Black Americans have disproportionately higher rates and earlier onset of Alzheimer's disease and related dementias (ADRD) relative to White Americans. We currently lack a comprehensive understanding of how the lived experience and broader societal factors, including cumulative exposure to structural racism and the mechanisms underlying the risks, may contribute to elevated ADRD risk in Black Americans.

METHODS

The Think PHRESH study builds on existing, community-based research infrastructure, from the ongoing Pittsburgh Hill/Homewood Research on Neighborhood Change and Health (PHRESH) studies, to examine the contributions of dynamic neighborhood socioeconomic conditions across the lifecourse to cognitive outcomes in mid- and late-life adults living in two historically disinvested, predominantly Black communities (anticipated n = 1133). This longitudinal, mixed-methods study rests on the premise that neighborhood racial segregation and subsequent disinvestment contributes to poor cognitive outcomes via factors including (a) low access to educational opportunities and (b) high exposure to race- and socioeconomically-relevant stressors, such as discrimination, trauma, and adverse childhood events. In turn, these cumulative exposures foster psychological vigilance in residents, leading to cardiometabolic dysregulation and sleep disruption, which may mediate associations between neighborhood disadvantage and ADRD risk. This premise recognizes the importance of potential protective factors that may promote cognitive health, including neighborhood social cohesion, safety, and satisfaction. The proposed study will leverage our existing longitudinal data on risk/protective factors and biobehavioral mediators and will include: (1) up to three waves of cognitive assessments in participants ages 50 years + and one assessment in participants ages 35-49 years; clinical adjudication of ADRD will be completed in participants who are 50+, (2) extensive surveys of risk and protective factors, (3) two assessments of blood pressure and objectively measured sleep, (4) a comprehensive assessment of life and residential history; and (5) two rounds of in-depth qualitative interviews to reveal lifecourse opportunities and barriers experienced by Black Americans in achieving optimal cognitive health in late life.

DISCUSSION

Understanding how structural racism has influenced the lived experience of Black Americans, including dynamic changes in neighborhood conditions over time, is critical to inform multi-level intervention and policy efforts to reduce pervasive racial and socioeconomic disparities in ADRD.

Nativity differences in the relationship between handgrip strength and cognitive impairment in older Mexican Americans over 20 years of follow-up

PURPOSE

To examine nativity differences in the relationship between handgrip strength (HGS) and cognitive impairment among Mexican Americans aged ≥ 65 years with normal or high cognitive function at baseline over a 20-year period.

METHODS

Prospective cohort study of 2,155 non-institutionalized Mexican Americans aged ≥ 65 years from the Hispanic Established Population for the Epidemiological Study of the Elderly) who scored ≥ 21 in the Mini Mental State Examination (MMSE) at baseline. Measures included socio-demographics, body mass index, medical conditions, depressive symptoms, physical function, disability, HGS quartiles (sex-adjusted), and MMSE. We used generalized estimating equation models to estimate the odds ratio (OR) and 95% Confidence Interval (CI) of cognitive impairment (MMSE < 21) as a function of HGS quartile by nativity and adjusted for covariates.

RESULTS

US-born and foreign-born participants in the 4th quartile (highest) of HGS at baseline had lower odds of cognitive impairment over time compared with those in the 1st (lowest) HGS quartile (OR=0.95, 95% CI=0.90-0.99 and OR=0.93, 95% CI=0.89-0.98, respectively), after controlling for all covariates. When we analyzed HGS quartiles as time-varying, we found that US-born participants in the 3rd and 4th HGS quartile had 25% and 30% lower odds of cognitive impairment, respectively, while foreign-born participants in the 3rd and 4th HGS quartile had 27% and 49% lower odds of cognitive impairment over time, respectively, after controlling for all covariates.

CONCLUSION

Foreign-born older Mexican Americans who performed high in HGS experienced 7% lower odds of cognitive impairment over time compared with US-born older Mexican Americans.

Harmonization of cognitive screening tools for dementia across diverse samples: A simulation study

Introduction

Research focusing on cognitive aging and dementia is a global endeavor. However, cross-national differences in cognition are embedded in other sociocultural differences, precluding direct comparisons of test scores. Such comparisons can be facilitated by co-calibration using item response theory (IRT). The goal of this study was to explore, using simulation, the necessary conditions for accurate harmonization of cognitive data.

Method

Neuropsychological test scores from the US Health and Retirement Study (HRS) and the Mexican Health and Aging Study (MHAS) were subjected to IRT analysis to estimate item parameters and sample means and standard deviations. These estimates were used to generate simulated item response patterns under 10 scenarios that adjusted the quality and quantity of linking items used in harmonization. IRT-derived factor scores were compared to the known population values to assess bias, efficiency, accuracy, and reliability of the harmonized data.

Results

The current configuration of HRS and MHAS data was not suitable for harmonization, as poor linking item quality led to large bias in both cohorts. Scenarios with more numerous and higher quality linking items led to less biased and more accurate harmonization.

Discussion

Linking items must possess low measurement error across the range of latent ability for co-calibration to be successful.

HIGHLIGHTS

We developed a statistical simulation platform to evaluate the degree to which cross-sample harmonization accuracy varies as a function of the quality and quantity of linking items.Two large studies of aging-one in Mexico and one in the United States-use three common items to measure cognition.These three common items have weak correspondence with the ability being measured and are all low in difficulty.Harmonized scores derived from the three common linking items will provide biased and inaccurate estimates of cognitive ability.Harmonization accuracy is greatest when linking items vary in difficulty and are strongly related to the ability being measured.

Alzheimer's disease genetic risk and cognitive reserve in relationship to long-term cognitive trajectories among cognitively normal individuals

BACKGROUND

Both Alzheimer's disease (AD) genetic risk factors and indices of cognitive reserve (CR) influence risk of cognitive decline, but it remains unclear whether they interact. This study examined whether a CR index score modifies the relationship between AD genetic risk factors and long-term cognitive trajectories in a large sample of individuals with normal cognition.

METHODS

Analyses used data from the Preclinical AD Consortium, including harmonized data from 5 longitudinal cohort studies. Participants were cognitively normal at baseline (M baseline age = 64 years, 59% female) and underwent 10 years of follow-up, on average. AD genetic risk was measured by (i) apolipoprotein-E (APOE) genetic status (APOE-ε2 and APOE-ε4 vs. APOE-ε3; N = 1819) and (ii) AD polygenic risk scores (AD-PRS; N = 1175). A CR index was calculated by combining years of education and literacy scores. Longitudinal cognitive performance was measured by harmonized factor scores for global cognition, episodic memory, and executive function.

RESULTS

In mixed-effects models, higher CR index scores were associated with better baseline cognitive performance for all cognitive outcomes. APOE-ε4 genotype and AD-PRS that included the APOE region (AD-PRSAPOE) were associated with declines in all cognitive domains, whereas AD-PRS that excluded the APOE region (AD-PRSw/oAPOE) was associated with declines in executive function and global cognition, but not memory. There were significant 3-way CR index score × APOE-ε4 × time interactions for the global (p = 0.04, effect size = 0.16) and memory scores (p = 0.01, effect size = 0.22), indicating the negative effect of APOE-ε4 genotype on global and episodic memory score change was attenuated among individuals with higher CR index scores. In contrast, levels of CR did not attenuate APOE-ε4-related declines in executive function or declines associated with higher AD-PRS. APOE-ε2 genotype was unrelated to cognition.

CONCLUSIONS

These results suggest that APOE-ε4 and non-APOE-ε4 AD polygenic risk are independently associated with global cognitive and executive function declines among individuals with normal cognition at baseline, but only APOE-ε4 is associated with declines in episodic memory. Importantly, higher levels of CR may mitigate APOE-ε4-related declines in some cognitive domains. Future research is needed to address study limitations, including generalizability due to cohort demographic characteristics.

Can vigilance predict the status of safe functional gait and risk of falls in patients with peripheral vestibular disorders? A cross-sectional study

OBJECTIVES

Peripheral vestibular disorders except from reflexes dysfunction correspond also to cognitive decline. The objectives of this cross-sectional study were to a) identify correlations among variables of functional gait, cognitive function, and perceived dizziness and b) explore variables that could be used as prognostic factors of functional gait in people with peripheral vestibular deficits.

METHODS

We recruited 154 people with peripheral vestibular deficits. The participants presented with moderate disability in terms of the Dizziness Handicap Inventory questionnaire (mean: 48.00, 95% confidence interval: 45.24-50.75), deficits in the Functional Gait Assessment test (mean: 22.75, 95% confidence interval: 22.13-23.40) and indication of mild cognitive impairment based on Montreal Cognitive Assessment tool (mean: 25.18, 95% confidence interval: 24.75-25.60).

RESULTS

Statistically significant correlations found among functional gait and gender, age, educational level, perceived level of disability and the total score of the Montreal Cognitive Assessment tool. Several components of the cognitive screening test (executive function, vigilance, language skills, verbal fluency) also correlated statistically significant with functional gait. Linear regression models revealed that age, perceived level of disability and vigilance significantly predicted functional gait variability (R² = 0.350; p < 0.001) as well as high risk of falling, as indicated by a score on Functional Gait Assessment test <22/30 (R² = 0.380).

CONCLUSIONS

Cognitive impairments affect functional gait in people with peripheral vestibular disorders. Thus, the integration of cognitive functional assessment must be considered as a prerequisite for functional assessment and designing rehabilitation programs that will include dual task training.

Harmonizing Ethno-Regionally Diverse Datasets to Advance the Global Epidemiology of Dementia

Understanding dementia and cognitive impairment is a global effort needing data from multiple sources across diverse ethno-regional groups. Methodological heterogeneity means that these data often require harmonization to make them comparable before analysis. We discuss the benefits and challenges of harmonization, both retrospective and prospective, broadly and with a focus on data types that require particular sorts of approaches, including neuropsychological test scores and neuroimaging data. Throughout our discussion, we illustrate general principles and give examples of specific approaches in the context of contemporary research in dementia and cognitive impairment from around the world.

Apolipoprotein E (APOE) genotype, dementia, and memory performance among Caribbean Hispanic versus US populations

INTRODUCTION

Apolipoprotein E (APOE) is considered the major susceptibility gene for developing Alzheimer's disease. However, the strength of this risk factor is not well established across diverse Hispanic populations.

METHODS

We investigated the associations among APOE genotype, dementia prevalence, and memory performance (immediate and delayed recall scores) in Caribbean Hispanics (CH), African Americans (AA), Hispanic Americans (HA) and non-Hispanic White Americans (NHW). Multivariable logistic regressions and negative binomial regressions were used to examine these associations by subsample.

RESULTS

Our final dataset included 13,516 participants (5198 men, 8318 women) across all subsamples, with a mean age of 74.8 years. Prevalence of APOE ε4 allele was similar in CHs, HAs, and NHWs (21.8%-25.4%), but was substantially higher in AAs (33.6%; P < 0.001). APOE ε4 carriers had higher dementia prevalence across all groups.

DISCUSSION

APOE ε4 was similarly associated with increased relative risk of dementia and lower memory performance in all subsamples.

Statistical harmonization of everyday functioning and dementia-related behavioral measures across nine surveys and trials

Introduction

Efforts to harmonize measures of everyday function and dementia-related behaviors are needed to synthesize across studies in dementia research. There have been some psychometric attempts to harmonize everyday function for secondary analysis, but far less for dementia-related behaviors.

Methods

Statistical co-calibration was performed to generate factor scores representing everyday function and dementia-related behaviors for participants with dementia. We evaluated convergent criterion validity of factor scores and mapped the scores onto established clinical instruments.

Results

Factor analyses of included items fit well to available data. Harmonized factors showed expected associations with the Global Clinical Dementia Rating (CDR) score, with greater impairment (higher Global CDR score) corresponding to higher (more severe) levels on factor scores.

Discussion

We used large, well-characterized samples to derive harmonized factors representing everyday functions and dementia-related behaviors. These harmonized factors can be used to tackle questions about dementia phenotypes which require either large samples or unique subpopulations.

Social determinants of memory change: A three-year follow-up of the Canadian Longitudinal Study on Aging (CLSA)

OBJECTIVES

Changes in memory can interfere with activities of daily living and may be indicative of serious health concerns such as mild cognitive impairment or dementia. Risk factors for cognitive decline and dementia have been shown to cluster around inequalities, suggesting that minority groups may be at an increased risk for cognitive decline. We sought to clarify the relationship between social determinants and change in memory function over a 3-year follow-up period, after accounting for demographic and health variables.

METHODS

We used baseline and first follow-up data from the Canadian Longitudinal Study on Aging (CLSA). Our primary analysis consisted of a multivariable linear regression model (n = 30,475). Demographic, health, education and occupation, social support, social identity, and social positioning variables (predictors) were measured at baseline. We computed a reliable change index (outcome) using the Rey Auditory Verbal Learning Test (RAVLT).

RESULTS

Older age and some health considerations (e.g., higher body mass index, low hearing) were associated with a greater decline in memory over the three-year period. In contrast, some physical activity and better self-rated general health were associated with improvements in memory. Having a hobby and better perceived social standing were associated with greater memory improvement. Social identities who experience minority stress (sexual orientation, gender identity, and race) did not predict change in memory.

DISCUSSION

Altogether, these results contribute to a growing body of evidence that points to older members of minoritized communities exhibiting initial differences in cognitive functioning (i.e., cross-sectional differences) but not more rapid cognitive aging.

Epidemiology and Risk Factors for Dementia

In this article, the authors discuss primarily what is known about the epidemiology of all-cause dementia. Dementia is caused by a complex interplay of genetics, comorbidities, and lifestyle factors, and drug development has been challenging. However, evidence from large, prospective, observational studies has identified a variety of factors that may prevent or delay the onset of dementia. Several of these factors are modifiable and lend themselves to well to treatments currently available. The authors discuss the state of current evidence on dementia risk factors, the most promising avenues, and future directions for dementia prevention and management.

Association of Plasma and Cerebrospinal Fluid Alzheimer Disease Biomarkers With Race and the Role of Genetic Ancestry, Vascular Comorbidities, and Neighborhood Factors

IMPORTANCE

Differences in cerebrospinal fluid (CSF) tau Alzheimer dementia (AD) biomarkers by self-identified race have been observed in prior studies. More recently, plasma biomarkers have been gaining recognition, but whether they exhibit similar differences is unclear. Furthermore, the underlying explanation for these differences in AD biomarkers is still unexplored.

OBJECTIVES

To investigate differences in plasma biomarkers by race and genetic ancestry and explore potential underlying explanations for these differences.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study used participant data from the Brain, Stress, Hypertension, and Aging Research Program (B-SHARP), an observational study conducted in the greater Atlanta metropolitan area. Participants were enrolled from March 1, 2016, to January 1, 2020.

MAIN OUTCOMES AND MEASURES

Main outcomes were plasma and CSF amyloid-β (Aβ) 42, Aβ40, phosphorylated tau181 (p-tau181), and neurofilament light. General linear models were used for key comparisons.

EXPOSURES

Main independent variables were self-identified race and genetic ancestry. Additional variables were cardiovascular factors, APOE4, educational attainment, Area Deprivation Index, and C-reactive protein (reflecting systemic inflammation state).

RESULTS

This analysis included 617 participants (mean [SD] age, 66 [7.9] years; 300 [49%] African American and 317 [51%] White; 429 [70%] with mild cognitive impairment). On the basis of self-reported race, plasma levels of Aβ42 (adjusted mean difference, -1.20 pg/mL; 95% CI, -2.33 to -0.07 pg/mL), Aβ40 (adjusted mean difference, -37.78 pg/mL; 95% CI, -60.16 to -15.39 pg/mL), p-tau181 (adjusted mean difference, -4.66 pg/mL; 95% CI, -7.05 to -1.90 pg/mL), and neurofilament light (adjusted mean difference, -1.58; 95% CI, -2.83 to -0.19 pg/mL) were consistently lower in African American individuals after adjusting for demographic characteristics, educational attainment, cognition, APOE4, and cardiovascular factors. A similar pattern was observed in the CSF biomarkers except for Aβ42 and Aβ40. Although unadjusted analyses revealed an association between these biomarkers and African ancestry, these associations were not significant after adjusting for the same covariates. Differences by self-reported race were not explained by varied cardiovascular risk factors, C-reactive protein, educational attainment, or Area Deprivation Index.

CONCLUSIONS AND RELEVANCE

In this cross-sectional study of plasma biomarkers by race and genetic ancestry, the results indicated that plasma p-tau181, Aβ40, and NFL were lower in African American individuals based on self-reported race but not genetic ancestry. These differences were not explained by cardiovascular risks or clinical stage differences. These racial differences should be considered in clinical interpretations and clinical trial screenings to avoid an additional increase in underrepresentation of African American individuals in AD trials.

Predictors of who Serves as an Alzheimer's Disease Research Participant's Study Partner and the Impact of their Relationship on Study Partners' Reports on Participants

Background: Alzheimer's disease and Alzheimer's disease related dementias (AD/ADRD) research typically requires participants to enroll with a "study partner" (SP). Little is known about what predicts who steps into the SP role or whether the SP's relationship to the participant affects their reports of disease severity.Methods: Health and Retirement Study data (HRS), collected prior to the Aging, Demographics and Memory Study (ADAMS), was used to identify sociocultural factors that predict who serves as a SP in ADAMS. SP-reported outcomes were compared between three types of participant-SP relationships: spousal, adult child, and other.Results: Spouses (35%) and adult children (39%) were similarly likely to serve as SPs. Factors predicting who served differed. In multivariable analyses, adult children rated participants less impaired than spouses on measures of memory, judgment, and organizational abilities (p < .05). Conclusions: The participant-SP relationship has independent effects on the SP's reports of the severity of cognitive impairments.

Race Inequity in School Attendance Across the Jim Crow South and Its Implications for Black-White Disparities in Trajectories of Cognitive Function Among Older Adults

OBJECTIVES

Although education is a key determinant of cognitive function, its role in determining Black-White disparities in cognitive function is unclear. This may be due, in part, to data limitations that have made it difficult to account for systemic educational inequities in the Jim Crow South experienced by older cohorts, including differences in the number of days Black students attended school compared to their White counterparts or Black peers in better-funded southern states. We determine if accounting for differential rates of school attendance across race, years, and states in the Jim Crow South better illuminates Black-White disparities in trajectories of cognitive function.

METHODS

We linked historical state-level data on school attendance from the 1919/1920 to 1953/1954 Biennial Surveys of Education to the Health and Retirement Study, a nationally representative, longitudinal study of U.S. adults older than age 50. We restricted our sample to Black and White older adults who attended school in the Jim Crow South and began primary school in/after 1919/1920 and completed primary/secondary school by 1953/1954 (n = 4,343). We used linear mixed models to estimate trajectories of total cognitive function, episodic memory, and working memory.

RESULTS

Self-reported years of schooling explained 28%-33% of the Black-White disparity in level of cognitive function, episodic memory, and working memory. Duration of school, a measure that accounted for differential rates of school attendance, explained 41%-55% of the Black-White disparity in these outcomes.

DISCUSSION

Our study highlights the importance of using a more refined measure of schooling for understanding the education-cognitive health relationship.

Collaborative Cohort of Cohorts for COVID-19 Research (C4R) Study: Study Design

The Collaborative Cohort of Cohorts for COVID-19 Research (C4R) is a national prospective study of adults comprising 14 established US prospective cohort studies. Starting as early as 1971, investigators in the C4R cohort studies have collected data on clinical and subclinical diseases and their risk factors, including behavior, cognition, biomarkers, and social determinants of health. C4R links this pre-coronavirus disease 2019 (COVID-19) phenotyping to information on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and acute and postacute COVID-related illness. C4R is largely population-based, has an age range of 18-108 years, and reflects the racial, ethnic, socioeconomic, and geographic diversity of the United States. C4R ascertains SARS-CoV-2 infection and COVID-19 illness using standardized questionnaires, ascertainment of COVID-related hospitalizations and deaths, and a SARS-CoV-2 serosurvey conducted via dried blood spots. Master protocols leverage existing robust retention rates for telephone and in-person examinations and high-quality event surveillance. Extensive prepandemic data minimize referral, survival, and recall bias. Data are harmonized with research-quality phenotyping unmatched by clinical and survey-based studies; these data will be pooled and shared widely to expedite collaboration and scientific findings. This resource will allow evaluation of risk and resilience factors for COVID-19 severity and outcomes, including postacute sequelae, and assessment of the social and behavioral impact of the pandemic on long-term health trajectories.

Effect of Aging on Educational Differences in the Risk of Cognitive Impairment: A Gender-Specific Analysis Using Korean Longitudinal Study of Aging (2006–2016)

This study examined the effect of aging on gender-specific educational differences in the risk of cognitive impairment using a nationally representative sample of 4278 men and 5495 women aged 45 years and older from the dataset of the Korean Longitudinal Study of Aging. Sociodemographics, lifestyle, and medical conditions were included as covariates in the mixed logistic regression analysis models. The prevalence of cognitive impairment was higher in women than in men at baseline. The risk of cognitive impairment in each age group decreased with education in both men and women. The risk by educational rank was worse at lower levels and increased with age, more so for women than men. Aging appears to widen the impact of educational differences on the risk of cognitive impairment and is more unfavorable for women than for men. Public health policies regarding population aging need to consider this and identify the target population to reduce both the level of and the difference in the risk of cognitive impairment.

Does a Cancer Diagnosis in Mid-to-Later Life Modify Racial Disparities in Memory Aging?

BACKGROUND

It is unknown whether an incident cancer diagnosis differentially impacts acute and long-term memory aging between older White and Black Americans.

METHODS

Incident cancer diagnoses and memory (immediate and delayed recall, combined with proxy-reported memory) were assessed at biennial study interviews in the US Health and Retirement Study (N=14,235, 1998-2016). We used multivariable segmented linear mixed-effects models to evaluate the rate of change in standardized memory score (SD/decade) in the years before, acutely at the time of, and in the years following an incident cancer diagnosis, compared to cancer-free adults, by race.

RESULTS

Black participants experienced faster memory decline than White participants (cancer-free group: -1.211 vs. -1.077; P<0.0001). An incident cancer diagnosis was associated with an acute memory drop in White, but not Black participants (-0.065 vs. 0.024; P<0.0001). However, White cancer survivors experienced slower memory decline than cancer-free White adults before and after diagnosis, but this memory advantage was not observed among Black cancer survivors.

CONCLUSIONS

Racial disparities in memory aging are not modified by an incident cancer diagnosis. The acute cancer-related memory decline and long-term memory advantage experienced by White, but not Black, cancer survivors relative to cancer-free older adults, requires further investigation.

The Role of Purpose in Life in the Relationship Between Widowhood and Cognitive Decline Among Older Adults in the U.S

OBJECTIVES

The objective of this study was to examine the role of purpose in life in the relationship between widowhood and cognitive decline.

METHODS

This study used a sample of 12,856 respondents (20,408 observations) collected from a national panel survey, the 2006-2014 waves of the Health and Retirement Study (HRS), that sampled older adults aged 50 or older. The study estimated growth-curve models with years since spousal death, purpose in life, and interaction between the two to predict cognition using three measures-total cognition, fluid, and crystallized intelligence scores. We also estimated growth-curve models by sex, race/ethnicity, and education.

RESULTS

While years since spousal death negatively correlated with cognition, purpose in life positively correlated with cognition. Furthermore, purpose in life had a moderating effect on the relationship between years since spousal death and cognition. This effect was found by using total cognition (coef. = 0.0515; z = 2.64; p < 0.01) and fluid intelligence scores (coef. = 0.0576; z = 3.23; p < 0.05). The same effects were salient among females (coef. = 0.0556; z = 2.19; p < 0.05), Whites (coef. = 0.0526; z = 2.52; p < 0.05), and older adults with more education (coef. = 0.0635; z = 2.10; p < 0.05).

CONCLUSION

Higher purpose in life relates to the negative correlations between widowhood and cognition of older adults. Educational programs improving purpose in life are a possible avenue for reducing the adverse effect of widowhood on cognition and warrant future exploration.

Is Old Age Just a Number in Language Skills? Language Performance and Its Relation to Age, Education, Gender, Cognitive Screening, and Dentition in Very Old Finnish Speakers

PURPOSE

This study reports on how very old (VO) Finnish people without dementia perform in the Western Aphasia Battery (WAB) and two verbal fluency tasks and which demographic factors predict the performance.

METHOD

The study included fifty 80- to 100-year-old community-dwelling Finnish speakers with no dementing illnesses or speech-language disabilities, who completed the WAB and two verbal fluency tasks. Multifactorial statistical analyses with recursive partitioning were carried out to determine the significant predictors out of five predictor variables (age, gender, education, dentition, and Mini-Mental State Examination [MMSE]) for four response variables (WAB Aphasia Quotient [AQ], Language Quotient [LQ], semantic, and phonemic word fluencies).

RESULTS

Overall, individual variation was notable in VO speakers. All predictor variables were statistically significantly associated with one or more of the language skills. Age was the most significant predictor; the critical age of 85-86 years was associated with a decline in WAB-AQ and semantic fluency. Poor dentition and the MMSE score both predicted a decline in WAB-LQ and phonemic fluency. A high level of education was positively associated with the skills of the best-performing individuals in WAB-AQ, WAB-LQ, and semantic fluency.

CONCLUSIONS

VO age is a significant factor contributing to language performance. However, a younger age, a good cognitive performance, intact teeth, and a higher educational level also seem to have a preservative power as regards language skills. Gender differences should be interpreted with caution. The results of this study provide culture- and language-specific normative data, which aids in differentiating typical aging from the signs of acute or degenerative neuropathology to ensure appropriate medical and therapeutic interventions.

Blood Pressure and Later-Life Cognition in Hispanic and White Adults (BP-COG): A Pooled Cohort Analysis of ARIC, CARDIA, CHS, FOS, MESA, and NOMAS

BACKGROUND

Ethnic differences in cognitive decline have been reported. Whether they can be explained by differences in systolic blood pressure (SBP) is uncertain.

OBJECTIVE

Determine whether cumulative mean SBP levels explain differences in cognitive decline between Hispanic and White individuals.

METHODS

Pooled cohort study of individual participant data from six cohorts (1971-2017). The present study reports results on SBP and cognition among Hispanic and White individuals. Outcomes were changes in global cognition (GC) (primary), executive function (EF) (secondary), and memory standardized as t-scores (mean [SD], 50 [10]); a 1-point difference represents a 0.1 SD difference in cognition. Median follow-up was 7.7 (Q1-Q3, 5.2-20.1) years.

RESULTS

We included 24,570 participants free of stroke and dementia: 2,475 Hispanic individuals (median age, cumulative mean SBP at first cognitive assessment, 67 years, 132.5 mmHg; 40.8% men) and 22,095 White individuals (60 years,134 mmHg; 47.3% men). Hispanic individuals had slower declines in GC, EF, and memory than White individuals when all six cohorts were examined. Two cohorts recruited Hispanic individuals by design. In a sensitivity analysis, Hispanic individuals in these cohorts had faster decline in GC, similar decline in EF, and slower decline in memory than White individuals. Higher time-varying cumulative mean SBP was associated with faster declines in GC, EF, and memory in all analyses. After adjusting for time-varying cumulative mean SBP, differences in cognitive slopes between Hispanic and White individuals did not change.

CONCLUSION

We found no evidence that cumulative mean SBP differences explained differences in cognitive decline between Hispanic and White individuals.

Alzheimer disease in African American individuals: increased incidence or not enough data?

Research on racial differences in Alzheimer disease (AD) dementia has increased in recent years. Older African American individuals bear a disproportionate burden of AD and cognitive impairment compared with non-Latino white individuals. Tremendous progress has been made over the past two decades in our understanding of the neurobiological substrates of AD. However, owing to well-documented challenges of study participant recruitment and a persistent lack of biological data in the African American population, knowledge of the drivers of these racial disparities has lagged behind. Therapeutic targets and effective interventions for AD are increasingly sought, but without a better understanding of the disease in African American individuals, any identified treatments and/or cures will evade this rapidly growing at-risk population. In this Perspective, I introduce three key obstacles to progress in understanding racial differences in AD: uncertainty about diagnostic criteria, disparate cross-sectional and longitudinal findings; and a dearth of neuropathological data. I also highlight evidence-informed strategies to move the field forward.

In this Perspective, Barnes introduces three key obstacles to progress in our understanding of racial differences in Alzheimer disease and highlights evidence-informed strategies that can move the field forward.

Biopsychosocial pathways in dementia inequalities: Introduction to the Michigan Cognitive Aging Project

Racial/ethnic inequalities in dementia risk are a major public health and health justice concern. Group differences that persist despite adjustment for socioeconomic and vascular indicators suggest that known dementia risk factors exhibit differential impact across race/ethnicity and/or there are unrecognized dementia risk factors that are racially patterned. This article provides targeted examples of both of these possibilities. First, depressive symptoms and white matter hyperintensities represent two known dementia risk factors that more strongly relate to negative cognitive outcomes among Black older adults than Whites, pointing to the need to consider contextual factors. Second, racial discrimination and external perceived control predict worse brain and cognitive aging above and beyond known risk factors. These psychosocial factors warrant explicit consideration in dementia cohort studies. Several challenges appear to be particularly relevant to the study of dementia inequalities, including selective survival and recruitment. These challenges complicate not only cross-study comparisons, but also within-study causal inferences. This article provides recommendations for addressing these challenges in order to accelerate high-quality research on dementia inequalities. Stemming from these recommendations, the article introduces the design and methods of the Michigan Cognitive Aging Project, a new, racially-balanced cohort study of Black and White adults transitioning to late life. In sum, careful research with community partners is needed to more fully explore the factors and contexts that create and sustain racial/ethnic disparities, as well as those that buffer against them. The ultimate goal of this research is to facilitate the dismantling of structural barriers to health justice for diverse older people. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Cognitive and metacognitive, motivational, and resource considerations for learning new skills across the lifespan

Across the lifespan, learners have to tackle the challenges of learning new skills. These skills can range from abilities needed for survival, such as learning languages, learning to walk during infancy, and learning new software for a job in adulthood, to abilities related to leisure and hobbies. As the learner progresses through novice to expert stages, there are cognitive and metacognitive, motivational, and resource considerations for learning new skills. In terms of cognitive considerations, fluid and crystallized abilities as well as executive functions interact to help the learner process and retain information related to the skills. In terms of metacognitive considerations, knowing what to learn and how to learn are important for novel skill learning. In terms of motivational considerations, changes in individuals' intrinsic and extrinsic motivation throughout the lifespan impact their pursuit of novel skill learning, and declines in motivation can be buffered through the cultivation of grit, growth mindset, self-efficacy, and other personal factors. In terms of resource considerations, there are many tools that learners can use to acquire new skills, but allocation and availability of these resources differ based on life stage and socioeconomic status. Taken together, these considerations may provide learners with the best chance at acquiring new skills across the lifespan. Further research investigating these three factors, particularly among older adult learners, and their interactive effects could help increase our understanding of their impacts on skill learning and inform future cognitive interventions that can be tailored to learners' unique needs. This article is categorized under: Cognitive Biology > Cognitive Development Psychology > Development and Aging Psychology > Learning.

Pre-statistical harmonization of behavrioal instruments across eight surveys and trials

BACKGROUND

Data harmonization is a powerful method to equilibrate items in measures that evaluate the same underlying construct. There are multiple measures to evaluate dementia related behavioral symptoms. Pre-statistical harmonization of behavioral instruments in dementia research is the first step to develop a statistical crosswalk between measures. Studies that conduct pre-statistical harmonization of behavioral instruments rarely document their methods in a structured, reproducible manner. This is a crucial step which entails careful review, documentation and scrutiny of source data to ensure sufficient comparability between items prior to data pooling. Here, we document the pre-statistical harmonization of items measuring behavioral and psychological symptoms among people with dementia. We provide a box of recommended procedure for future studies.

METHODS

We identified behavioral instruments that are used in clinical practice, a national survey, and randomized trials of dementia care interventions. We rigorously reviewed question content and scoring procedures to establish sufficient comparability across items as well as item quality prior to data pooling. Additionally, we standardized coding to Stata-readable format, which allowed us to automate approaches to identify potential cross-study differences in items and low-quality items. To ensure reasonable model fit for statistical co-calibration, we estimated two-parameter logistic Item Response Theory models within each of the eight studies.

RESULTS

We identified 59 items from 11 behavioral instruments across the eight datasets. We found considerable cross-study heterogeneity in administration and coding procedures for items that measure the same attribute. Discrepancies existed in terms of directionality and quantification of behavioral symptoms for even seemingly comparable items. We resolved item response heterogeneity, missingness and skewness, conditional dependency prior to estimation of item response theory models for statistical co-calibration. We used several rigorous data transformation procedures to address these issues, including re-coding and truncation.

CONCLUSIONS

This study highlights the importance of each aspect involved in the pre-statistical harmonization process of behavioral instruments. We provide guidelines and recommendations for how future research may detect and account for similar issues in pooling behavioral and related instruments.

Ethnoracial disparities in cognition are associated with multiple socioeconomic status-stress pathways

Systemic racism can have broad impacts on health in ethnoracial minorities. One way is by suppressing socioeconomic status (SES) levels through barriers to achieve higher income, wealth, and educational attainment. Additionally, the weathering hypothesis proposes that the various stressful adversities faced by ethnoracial minorities lead to greater wear and tear on the body, known as allostatic load. In the present study, we extend these ideas to cognitive health in a tri-ethnic sample of young adults-when cognition and brain health is arguably at their peak. Specifically, we tested competing mediation models that might shed light on how two key factors caused by systemic racism-SES and perceived stress-intersect to explain ethnoracial disparities in cognition. We found evidence for partial mediation via a pathway from SES to stress on episodic memory, working memory capacity, and executive function in Black Americans relative to non-Hispanic White Americans. Additionally, we found that stress partially mediated the ethnoracial disparities in working memory updating for lower SES Black and Hispanic Americans relative to non-Hispanic White Americans, showing that higher SES can sometimes reduce the negative effects stress has on these disparities in some cognitive domains. Overall, these findings suggest that multiple pathways exist in which lower SES creates a stressful environment to impact ethnoracial disparities cognition. These pathways differ depending on the specific ethnoracial category and cognitive domain. The present results may offer insight into strategies to help mitigate the late-life risk for neurocognitive disorders in ethnoracial minorities.

Minority Women

Perceptions of illness, pain, and death are not static. They vary among populations according to their cultural and biological characteristics. Older black and Hispanic/Latinx women are unique in their approach to health care with respect to mentation, mobility, medication adherence, and what matters to them. It is the complexity of these components, which affect the ability of these women to age gracefully.

Associations between education and dementia in the Caribbean and the United States: An international comparison

INTRODUCTION

Despite high dementia prevalence in Hispanic populations globally, especially Caribbean Hispanics, no study has comparatively examined the association between education and dementia among Hispanics living in the Caribbean Islands and older adults in the United States.

METHODS

We used data on 6107 respondents aged 65 and older in the baseline wave of the population-based and harmonized 10/66 survey from Cuba, the Dominican Republic, and Puerto Rico, collected between 2003 and 2008, and 11,032 respondents aged 65 and older from the U.S.-based Health and Retirement Study data in 2014, a total of 17,139 individuals. We estimated multivariable logistic regression models examining the association between education and dementia, adjusted for age, income, assets, and occupation. The models were estimated separately for the Caribbean population (pooled and by setting) and the U.S. population by race/ethnicity (Hispanic, Black, and White), followed by pooled models across all populations.

RESULTS

In the Caribbean population, the relative risk of dementia among low versus high educated adults was 1.45 for women (95% confidence interval [CI] 1.17, 1.74) and 1.92 (95% CI 1.35, 2.49) for men, smaller compared to those in the United States, especially among non-Hispanic Whites (women: 2.78, 95% CI 1.94, 3.61; men: 5.98, 95% CI 4.02, 7.95).

DISCUSSION

The differential associations between education and dementia across the Caribbean and US settings may be explained by greater disparities in social conditions in the United States compared to the Caribbean, such as access to health care, healthy behaviors, and social stressors, which serve as potentially important mediators.

Racial segregation and cognitive function among older adults in the United States: Findings from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study

OBJECTIVES

Residential segregation is one of the fundamental features of health disparities in the United States. Yet little research has examined how living in segregated metropolitan areas is related to cognitive function and cognitive decline with age. We examined the association between segregation at the Metropolitan Statistical Area (MSA) level and trajectories of age-related cognitive function.

METHOD

Using data from Black and White older adults in the REasons for Geographic and Racial Differences in Stroke (REGARDS) study (n=18,913), we employed linear growth curve models to examine how living in racially segregated MSAs at baseline, measured by the degree of Non-Hispanic Black [NHB] isolation and NHB dissimilarity, was associated with trajectories of age-related cognitive function and how the associations varied by race and education.

RESULTS

Living in MSAs with greater levels of isolation was associated with lower cognitive function (b=-0.093, p<0.05) but was not associated with rates of change in cognitive decline with age. No effects of living in isolated MSAs were found for those with at least a high school education, but older adults with less than a high school education had lower cognitive function in MSAs with greater isolation (b=-0.274, p<0.05). The degree of dissimilarity was not associated with cognitive function. The association between segregation and cognitive function did not vary by race.

DISCUSSION

Metropolitan segregation was associated with lower cognitive function among older adults, especially for those with lower education living in racially isolated MSAs. This suggests complex associations between individual socioeconomic status, place, and cognitive health.

Comparison of Education and Episodic Memory as Modifiers of Brain Atrophy Effects on Cognitive Decline: Implications for Measuring Cognitive Reserve

OBJECTIVE

This study compared the level of education and tests from multiple cognitive domains as proxies for cognitive reserve.

METHOD

The participants were educationally, ethnically, and cognitively diverse older adults enrolled in a longitudinal aging study. We examined independent and interactive effects of education, baseline cognitive scores, and MRI measures of cortical gray matter change on longitudinal cognitive change.

RESULTS

Baseline episodic memory was related to cognitive decline independent of brain and demographic variables and moderated (weakened) the impact of gray matter change. Education moderated (strengthened) the gray matter change effect. Non-memory cognitive measures did not incrementally explain cognitive decline or moderate gray matter change effects.

CONCLUSIONS

Episodic memory showed strong construct validity as a measure of cognitive reserve. Education effects on cognitive decline were dependent upon the rate of atrophy, indicating education effectively measures cognitive reserve only when atrophy rate is low. Results indicate that episodic memory has clinical utility as a predictor of future cognitive decline and better represents the neural basis of cognitive reserve than other cognitive abilities or static proxies like education.

Educational Benefits and Cognitive Health Life Expectancies: Racial/Ethnic, Nativity, and Gender Disparities

BACKGROUND AND OBJECTIVES

To examine racial/ethnic, nativity, and gender differences in the benefits of educational attainment on cognitive health life expectancies among older adults in the United States.

RESEARCH DESIGN AND METHODS

We used data from the Health and Retirement Study (1998-2014) to estimate Sullivan-based life tables of cognitively healthy, cognitively impaired/no dementia, and dementia life expectancies by gender for older White, Black, U.S.-born Hispanic, and foreign-born Hispanic adults with less than high school, high school, and some college or more.

RESULTS

White respondents lived a greater percentage of their remaining lives cognitively healthy than their minority Black or Hispanic counterparts, regardless of level of education. Among respondents with some college or more, versus less than high school, Black and U.S.-born Hispanic women exhibited the greatest increase (both 37 percentage points higher) in the proportion of total life expectancy spent cognitively healthy; whereas White women had the smallest increase (17 percentage points higher). For men, the difference between respondents with some college or more, versus less than high school, was greatest for Black men (35 percentage points higher) and was lowest for U.S.-born Hispanic men (21 percentage points higher).

DISCUSSION AND IMPLICATIONS

Our results provide evidence that the benefits of education on cognitive health life expectancies are largest for Black men and women and U.S.-born Hispanic women. The combination of extended longevity and rising prevalence of Alzheimer's disease points to the need for understanding why certain individuals spend an extended period of their lives with poor cognitive health.

Measuring cognitive health in ethnically diverse older adults

OBJECTIVE

Understanding racial/ethnic disparities in late-life cognitive health is a public health imperative. We used baseline data from the Kaiser Healthy Aging and Diverse Life Experiences (KHANDLE) study to examine how age, education, gender, and clinical diagnosis, a proxy for brain health, are associated with cross-sectional measures of cognition in diverse racial/ethnic groups.

METHOD

Comprehensive measures of cognition were obtained using the Spanish and English Neuropsychological Assessment Scales and the NIH Toolbox Cognitive Health Battery in a sample of 1695 KHANDLE participants (Asians 24%, Blacks 26%, Latinos 20%, Whites 29%). A 25% random subsample was clinically evaluated and diagnosed with normal cognition, mild cognitive impairment (MCI), or dementia. Cognitive test scores were regressed on core demographic variables and diagnosis in the combined sample and in multiple group analyses stratified by racial/ethnic group.

RESULTS

Race/ethnicity and education were variably associated with test scores with strongest associations with tests of vocabulary and semantic memory. Older age was associated with poorer performance on all measures, and gender differences varied across cognitive tests. Clinical diagnosis of MCI or dementia was associated with average decrements in test scores that ranged from -0.41 to -0.84 SD, with largest differences on tests of executive function and episodic memory. With few exceptions, associations of demographic variables and clinical diagnosis did not differ across racial/ethnic groups.

DISCUSSION

The robust associations of cognitive test results with clinical diagnosis independent of core demographic variables and race/ethnicity supports the validity of cognitive tests as indicators for brain health in diverse older adults.

Do the Benefits of Educational Attainment for Late-life Cognition Differ by Racial/Ethnic Group?: Evidence for Heterogenous Treatment Effects in the Kaiser Healthy Aging and Diverse Life Experience (KHANDLE) Study

INTRODUCTION

Educational attainment is associated with late-life cognitive performance and dementia; few studies have examined diverse racial/ethnic groups to assess whether the association differs by race/ethnicity.

METHODS

We investigated whether the association between educational attainment and cognition differed between White, Black, Asian, and Latino participants in the Kaiser Healthy Aging and Diverse Life Experiences study (n=1348). Covariate-adjusted multivariable linear regression models examined domains of verbal episodic memory, semantic memory, and executive functioning.

RESULTS

We observed significant effect heterogeneity by race/ethnicity only for verbal episodic memory (P=0.0198), for which any schooling between high school and college was beneficial for White, Asian, and Black participants, but not Latino participants. We found no evidence of heterogeneity for semantic memory or executive function.

DISCUSSION

With the exception of Latino performance on verbal episodic memory, more education consistently predicted better cognitive scores to a similar extent across racial/ethnic groups, despite likely heterogenous educational and social experiences.

Cognitive profiles in older males and females

Males and females are subject to differences in cognitive processing strategies, i.e. the way males and females solve cognitive tasks. So far primarily reported for younger adults, this seems to be especially important in older adults, who also show sex differences in cognitive impairments. Therefore, the aim of the current study was to examine the older adult population with respect to cognitive profiles derived from a large variety of cognitive functions. Using an exploratory component analysis with consecutive confirmatory factor analysis in a sample of 676 older adults, neuropsychological performance data in a variety of cognitive domains was decomposed into cognitive components. A general cognitive profile based on the whole group fits unequally well on the two sexes. Importantly, cognitive profiles based on either males or females differ in terms of their composition of cognitive components, i.e. three components in males versus four components in females, with a generally better model fit in females. Thus, related to the established differences in processing styles between males and females the current study found a rather decomposed (or local) cognitive profile in females while males seem to show a holistic (or global) cognitive profile, with more interrelations between different cognitive functions.

Collaborative Cohort of Cohorts for COVID-19 Research (C4R) Study: Study Design

The Collaborative Cohort of Cohorts for COVID-19 Research (C4R) is a national prospective study of adults at risk for coronavirus disease 2019 (COVID-19) comprising 14 established United States (US) prospective cohort studies. For decades, C4R cohorts have collected extensive data on clinical and subclinical diseases and their risk factors, including behavior, cognition, biomarkers, and social determinants of health. C4R will link this pre-COVID phenotyping to information on SARS-CoV-2 infection and acute and post-acute COVID-related illness. C4R is largely population-based, has an age range of 18-108 years, and broadly reflects the racial, ethnic, socioeconomic, and geographic diversity of the US. C4R is ascertaining severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and COVID-19 illness using standardized questionnaires, ascertainment of COVID-related hospitalizations and deaths, and a SARS-CoV-2 serosurvey via dried blood spots. Master protocols leverage existing robust retention rates for telephone and in-person examinations, and high-quality events surveillance. Extensive pre-pandemic data minimize referral, survival, and recall bias. Data are being harmonized with research-quality phenotyping unmatched by clinical and survey-based studies; these will be pooled and shared widely to expedite collaboration and scientific findings. This unique resource will allow evaluation of risk and resilience factors for COVID-19 severity and outcomes, including post-acute sequelae, and assessment of the social and behavioral impact of the pandemic on long-term trajectories of health and aging.

The Effect of Diabetes on the Cognitive Trajectory of Older Adults in Mexico and the United States

OBJECTIVES

To study the impact of diabetes on the long-term cognitive trajectories of older adults in 2 countries with different socioeconomic and health settings, and to determine whether this relationship differs by cognitive domains. This study uses Mexico and the United States to confirm if patterns hold in both populations, as these countries have similar diabetes prevalence but different socioeconomic conditions and diabetes-related mortality.

METHODS

Two nationally representative cohorts of adults aged 50 years or older are used: the Mexican Health and Aging Study for Mexico and the Health and Retirement Study for the United States, with sample sizes of 18,810 and 26,244 individuals, respectively, followed up for a period of 14 years. The outcome is cognition measured as a total composite score and by domain (memory and nonmemory). Mixed-effect linear models are used to test the effect of diabetes on cognition at 65 years old and over time in each country.

RESULTS

Diabetes is associated with lower cognition and nonmemory scores at baseline and over time in both countries. In Mexico, diabetes only predicts lower memory scores over time, whereas in the United States it only predicts lower memory scores at baseline. Women have higher total cognition and memory scores than men in both studies. The magnitude of the effect of diabetes on cognition is similar in both countries.

DISCUSSION

Despite the overall lower cognition in Mexico and different socioeconomic characteristics, the impact of diabetes on cognitive decline and the main risk and protective factors for poor cognition are similar in both countries.

Cognitive reserve and Alzheimer's biological continuum: clues for prediction and prevention of dementia

Cognitive reserve is originally an epidemiological concept that encompasses individual abilities to cope with changes. It is considered the result of a balance between processes of cellular damage and repair, and its description raised much interest in predicting and preventing cognitive decline in aging and Alzheimer's disease (AD). In this study, we discussed the concept of cognitive reserve considering the recent definition of AD as a biological continuum and suggest that the protection of cognitive reserve may result from efficient synaptic plasticity mechanisms. Despite pathological changes of AD appearing very early during life, long before the onset of cognitive symptoms, different variables act together to keep repair mechanisms effective guaranteeing successful aging if environmental enrichment is maintained.

African Americans Have Differences in CSF Soluble TREM2 and Associated Genetic Variants

Objective

To evaluate for racial differences in triggering receptor expressed on myeloid cells 2 (TREM2), a key immune mediator in Alzheimer disease, the levels of CSF soluble TREM2 (sTREM2), and the frequency of associated genetic variants were compared in groups of individuals who self-reported their race as African American (AA) or non-Hispanic White (NHW).

Methods

Community-dwelling older research participants underwent measurement of CSF sTREM2 concentrations and genetic analyses.

Results

The primary cohort included 91 AAs and 868 NHWs. CSF sTREM2 levels were lower in the AA compared with the NHW group (1,336 ± 470 vs 1,856 ± 624 pg/mL, p < 0.0001). AAs were more likely to carry TREM2 coding variants (15% vs 3%, p < 0.0001), which were associated with lower CSF sTREM2. AAs were less likely to carry the rs1582763 minor allele (8% vs 37%, p < 0.0001), located near MS4A4A, which was associated with higher CSF sTREM2. These findings were replicated in an independent cohort of 23 AAs and 917 NHWs: CSF sTREM2 levels were lower in the AA group (p = 0.03), AAs were more likely to carry coding TREM2 variants (22% vs 4%, p = 0.002), and AAs were less likely to carry the rs1582763 minor allele (16% vs 37%, p = 0.003).

Conclusions

On average, AAs had lower CSF sTREM2 levels compared with NHWs, potentially because AAs are more likely to carry genetic variants associated with lower CSF sTREM2 levels. Importantly, CSF sTREM2 reflects TREM2-mediated microglial activity, a critical step in the immune response to amyloid plaques. These findings suggest that race may be associated with risk for genetic variants that influence Alzheimer disease–related inflammation.