Socioeconomic Status, Biological Aging, and Memory in a Diverse National Sample of Older US Men and Women

Telomere Length and Cognitive Function Among Middle-Aged and Older Participants From Communities Underrepresented in Aging Research: A Preliminary Study

ObjectiveAccelerated biological aging is a plausible and modifiable determinant of dementia burden facing minoritized communities but is not well-studied in these historically underrepresented populations. Our objective was to preliminarily characterize relationships between telomere length and cognitive health among American Indian/Alaska Native (AI/AN) and Black/African American (B/AA) middle-aged and older adults.MethodsThis study included data on telomere length and neuropsychological test performance from 187 participants, enrolled in one of two community-based cognitive aging cohorts and who identified their primary race as AI/AN or B/AA.ResultsNested multivariable regression models revealed preliminary evidence for associations between telomere length and cognitive performance, and these associations were partially independent of chronological age.DiscussionSmall sample size limited estimate precision; however, findings suggest future work on telomere length and cognitive health in underrepresented populations at high risk for dementia is feasible and valuable as a foundation for social and behavioral intervention research.

Sex and education differences in trajectories of physiological ageing: longitudinal analysis of a prospective English cohort study

BACKGROUND

Physiological age (PA) derived from clinical indicators including blood-based biomarkers and tests of physiological function can be compared with chronological age to examine disparities in health between older adults of the same age. Though education interacts with sex to lead to inequalities in healthy ageing, their combined influence on longitudinally measured PA has not been explored. We derived PA based on longitudinally measured clinical indicators and examined how sex and education interact to inform PA trajectories.

METHODS

Three waves of clinical indicators (2004/05-2012/13) drawn from the English Longitudinal Study of Ageing (ages 50-100 years) were used to estimate PA, which was internally validated by confirming associations with incident chronic conditions, functional limitations and memory impairment after adjustment for chronological age and sex. Joint models were used to construct PA trajectories in 8891 English Longitudinal Study of Ageing participants to examine sex and educational disparities in PA.

FINDINGS

Amongst the least educated participants, there were negligible sex differences in PA until age 60 (sex difference [men-women] age 50 = -0.6 years [95% confidence interval = -2.2 to 0.6]; age 60 = 0.4 [-0.6 to 1.4]); at age 70, women were 1.5 years (0.7-2.2) older than men. Amongst the most educated participants, women were 3.8 years (1.6-6.0) younger than men at age 50 and 2.7 years (0.4-5.0) younger at age 60, with a nonsignificant sex difference at age 70.

INTERPRETATION

Higher education provides a larger midlife buffer to physiological ageing for women than men. Policies to promote gender equity in higher education may contribute to improving women's health across a range of ageing-related outcomes.

Construction of brain age models based on structural and white matter information

Brain aging is an inevitable process in adulthood, yet there is a lack of objective measures to accurately assess its extent. This study aims to develop brain age prediction model using magnetic resonance imaging (MRI), which includes structural information of gray matter and integrity information of white matter microstructure. Multiparameter MRI was performed on two population cohorts. We collected structural MRI data from T1- and T2-sequences, including gray matter volume, surface area, and thickness in different areas. For diffusion tensor imaging (DTI), we derived four white matter parameters: fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. To achieve reliable brain age prediction based on structure and white matter integrity, we employed LASSO regression. We successfully constructed a brain age prediction model based on multiparameter brain MRI (Mean absolute error of 3.87). Using structural and diffusion metrics, we identified and visualized which brain areas were notably involved in brain aging. Simultaneously, we discovered that lateralization during brain aging is a significant factor in brain aging models. We have successfully developed a brain age estimation model utilizing white matter and gray matter metrics, which exhibits minimal errors and is suitable for adults.

Social disadvantage accelerates aging

Social disadvantage, like advanced age, is a risk factor for a broad range of health conditions; however, whether it influences the aging process remains unclear. Here, using a multicohort approach, we investigated the associations of social disadvantage with age-related plasma proteins and age-related diseases. We found proteomic signatures of accelerated immune aging and 14 specific age-related proteins linked to social disadvantage during both early and later life. Individuals experiencing social disadvantage had an increased risk of 66 age-related diseases, with up to 39% of these associations mediated by the 14 age-related proteins (for example, DNAJB9, F2, HSPA1A, BGN). The main enriched pathway involved the upregulation of the pro-inflammatory regulator NF-κB24 and its downstream factor interleukin-8. Our findings support the hypothesis that social disadvantage throughout the life course may accelerate aging, a biological mechanism that could explain why social stratification plays such a fundamental role in determining human health.

Neighborhood environment and cognitive functioning in middle-aged and older population: A mediating role of physical activity

BACKGROUND

Evidence on the impact of complex neighborhood environment, including air pollution, greenness, and neighborhood socioeconomic deprivation (nSED) on cognitive health in older adults remains scarce. Both cognition and neighborhood environment are associated with physical activity, but little is known about the potential mediating role of physical activity in this association.

METHODS

Cross-sectional data of the Czech arm of the HAPIEE cohort study examined 4,178 participants (55.6% women) aged 45-69 years. Global cognitive score was constructed from memory, verbal fluency, and concentration domains. The exposures, assigned to participant's addresses, include 4-year (2000-2003) average concentrations of PM2.5, greenness index calculated from tree crown canopy cover estimation (2000), and census-based nSED characteristics. Physical activity and other covariates were assessed by a questionnaire. Structural equation modelling was used to estimate standardized β coefficients for the relationships between neighborhood environment, physical activity and cognitive performance.

RESULTS

After controlling for a range of covariates, global cognitive function was inversely associated with PM2.5 (β = -0.087; 95%CI: 0.122 to -0.052) and nSED (β = -0.147; 95%CI: 0.182 to -0.115), and positively associated with greenness (β = 0.036; 95%CI: 0.001 to 0.069). We identified a weak but statistically significant mediating role of physical activity in the associations of PM2.5 exposures and nSED on global cognitive score. Total mediation proportions ranged from 3.9% to 6.5% for nSED and PM2.5, respectively.

CONCLUSIONS

The neighborhood environment was associated with cognitive health in older individuals; the associations were partially mediated by physical activity.

Rethinking the residual approach: leveraging statistical learning to operationalize cognitive resilience in Alzheimer's disease

Cognitive resilience (CR) describes the phenomenon of individuals evading cognitive decline despite prominent Alzheimer's disease neuropathology. Operationalization and measurement of this latent construct is non-trivial as it cannot be directly observed. The residual approach has been widely applied to estimate CR, where the degree of resilience is estimated through a linear model's residuals. We demonstrate that this approach makes specific, uncontrollable assumptions and likely leads to biased and erroneous resilience estimates. This is especially true when information about CR is contained in the data the linear model was fitted to, either through inclusion of CR-associated variables or due to correlation. We propose an alternative strategy which overcomes the standard approach's limitations using machine learning principles. Our proposed approach makes fewer assumptions about the data and CR and achieves better estimation accuracy on simulated ground-truth data.

Genetic variants associated with age-related episodic memory decline implicate distinct memory pathologies

BACKGROUND

Approximately 40% of people aged ≥ 65 experience memory loss, particularly in episodic memory. Identifying the genetic basis of episodic memory decline is crucial for uncovering its underlying causes.

METHODS

We investigated common and rare genetic variants associated with episodic memory decline in 742 (632 for rare variants) Ashkenazi Jewish individuals (mean age 75) from the LonGenity study. All-atom molecular dynamics simulations were performed to uncover mechanistic insights underlying rare variants associated with episodic memory decline.

RESULTS

In addition to the common polygenic risk of Alzheimer's disease, we identified and replicated rare variant associations in ITSN1 and CRHR2. Structural analyses revealed distinct memory pathologies mediated by interfacial rare coding variants such as impaired receptor activation of corticotropin releasing hormone and dysregulated L-serine synthesis.

DISCUSSION

Our study uncovers novel risk loci for episodic memory decline. The identified underlying mechanisms point toward heterogenous memory pathologies mediated by rare coding variants.

HIGHLIGHTS

We demonstrated the contribution of the common polygenic risk of Alzheimer's disease to episodic memory decline. We discovered and replicated two risk genes associated with episodic memory decline implicated by rare variants, were discovered and replicated. We demonstrated molecular mechanisms and potential novel memory pathologies underlying interfacial rare coding variants. Molecular dynamics simulations were performed to understand the downstream effects of risk rare coding variants.

The Pace of Biological Aging Partially Explains the Relationship Between Socioeconomic Status and Chronic Low Back Pain Outcomes

Introduction

Having a lower socioeconomic status (SES) is a predictor of age-related chronic conditions, including chronic low back pain (cLBP). We aimed to examine whether the pace of biological aging mediates the relationship between SES and cLBP outcomes - pain intensity, pain interference, and physical performance.

Methods

We used the Dunedin Pace of Aging Calculated from the Epigenome (DunedinPACE) software to determine the pace of biological aging in adults ages 18 to 85 years with no cLBP (n = 74), low-impact pain (n = 56), and high-impact pain (n = 77).

Results

The mean chronological age of the participants was 40.9 years (SD= 15.1); 107 (51.7%) were female, and 108 (52.2%) were Black. On average, the pace of biological aging was 5% faster [DunedinPACE = 1.05 (SD = 0.14)] in the sample (DunedinPACE value of 1 = normal pace of aging). Individuals with higher levels of education had a significantly slower pace of biological aging than those with lower education levels (F = 5.546, p = 0.001). After adjusting for sex and race, household income level significantly correlated with the pace of biological aging (r = -0.17, p = 0.02), pain intensity (r = -0.21, p = 0.003), pain interference (r = -0.21, p = 0.003), and physical performance (r = 0.20, p = 0.005). In mediation analyses adjusting for sex, race, and body mass index (BMI), the pace of biological aging mediates the relationship between household income (but not education) level and cLBP intensity, interference, as well as physical performance.

Discussion

Results indicate that lower SES contributes to faster biological aging, possibly contributing to greater pain intensity and interference, as well as lower physical performance. Future interventions slowing the pace of biological aging may improve cLBP outcomes.

Development of a novel transcriptomic measure of aging: Transcriptomic Mortality-risk Age (TraMA)

Increasingly, research suggests that aging is a coordinated multi-system decline in functioning that occurs at multiple biological levels. We developed and validated a transcriptomic (RNA-based) aging measure we call Transcriptomic Mortality-risk Age (TraMA) using RNA-seq data from the 2016 Health and Retirement Study using elastic net Cox regression analyses to predict 4-year mortality hazard. In a holdout test sample, TraMA was associated with earlier mortality, more chronic conditions, poorer cognitive functioning, and more limitations in activities of daily living. TraMA was also externally validated in the Long Life Family Study and several publicly available datasets. Results suggest that TraMA is a robust, portable RNAseq-based aging measure that is comparable, but independent from past biological aging measures (e.g., GrimAge). TraMA is likely to be of particular value to researchers interested in understanding the biological processes underlying health and aging, and for social, psychological, epidemiological, and demographic studies of health and aging.

The role of Southern context in shaping life course exposures linked to dementia incidence for Black and White older adults in the United States

While racial inequities in dementia risk are well-documented in the United States, research has paid less attention to role of US Southern context in shaping dementia risk through life course exposures. In this study, we examine how Southern birth and Southern residence in adulthood are linked to dementia incidence for Black and White older adults in the United States. Using the Health and Retirement Study (N = 15,613), we estimate a series of hazard models to evaluate how life course risk factors such as childhood health and social disadvantage, education, adult socioeconomic status, health behaviors, and cardiometabolic conditions impact the association between Southern life course residency and dementia risk. We find different patterns in how Southern life course context shapes dementia risk among Black and White adults, with dementia risk among Blacks especially sensitive to combinations of Southern life course context. These findings demonstrate the importance of considering potential heterogenous life course pathways to cognitive aging and health that may be shaped by larger socio-historical experiences.

A Review of the Public Health Literature Examining the Roles of Socioeconomic Status and Race/Ethnicity on Health Outcomes in the United States

This review of reviews examines the role of socioeconomic status (SES) indicators on health inequities among different racial and ethnic groups in the United States (US) between 2019 and 2023. Of the 419 articles, 27 reviews met the inclusion criteria and were aggregated into seven categories: COVID-19 and respiratory pandemic disparities; neighborhoods, gentrification, and food environment; surgical treatments; mental, psychological, and behavioral health; insurance, access to care, and policy impact; cancers; and other topics. The findings revealed a documented impact of SES indicators on racial/ethnic health inequities, with racial/ethnic minority communities, especially Black Americans, consistently showing poor health outcomes associated with lower SES, regardless of the outcome or indicator examined. These findings call attention to the importance of policies and practices that address socioeconomic factors and systemic racial/ethnic inequities affecting the social determinants of health affecting racial/ethnic inequities to improve health outcomes in the US population.

Telomere length and cognitive function among middle-aged and older participants from communities underrepresented in aging research: A preliminary study

Objective

Accelerated biological aging is a plausible and modifiable determinant of dementia burden facing minoritized communities, but is not well-studied in these historically underrepresented populations. Our objective was to preliminarily characterize relationships between telomere length and cognitive health among American Indian/Alaska Native (AI/AN) and Black/African American (B/AA) middle-aged and older adults.

Methods

This study included data on telomere length and cognitive test performance from 187 participants, enrolled in one of two community-based cognitive aging cohorts and who identified their primary race as AI/AN or B/AA.

Results

Nested multivariable regression models revealed preliminary evidence for associations between telomere length and cognitive performance, and these associations were partially independent of chronological age.

Discussion

Small sample size limited estimate precision, however, findings suggest future work on telomere length and cognitive health in underrepresented populations at high risk for dementia is feasible and valuable as a foundation for social and behavioral intervention research.

Bridging the gap: Multi-omics profiling of brain tissue in Alzheimer's disease and older controls in multi-ethnic populations

INTRODUCTION

Multi-omics studies in Alzheimer's disease (AD) revealed many potential disease pathways and therapeutic targets. Despite their promise of precision medicine, these studies lacked Black Americans (BA) and Latin Americans (LA), who are disproportionately affected by AD.

METHODS

To bridge this gap, Accelerating Medicines Partnership in Alzheimer's Disease (AMP-AD) expanded brain multi-omics profiling to multi-ethnic donors.

RESULTS

We generated multi-omics data and curated and harmonized phenotypic data from BA (n = 306), LA (n = 326), or BA and LA (n = 4) brain donors plus non-Hispanic White (n = 252) and other (n = 20) ethnic groups, to establish a foundational dataset enriched for BA and LA participants. This study describes the data available to the research community, including transcriptome from three brain regions, whole genome sequence, and proteome measures.

DISCUSSION

The inclusion of traditionally underrepresented groups in multi-omics studies is essential to discovering the full spectrum of precision medicine targets that will be pertinent to all populations affected with AD.

HIGHLIGHTS

Accelerating Medicines Partnership in Alzheimer's Disease Diversity Initiative led brain tissue profiling in multi-ethnic populations. Brain multi-omics data is generated from Black American, Latin American, and non-Hispanic White donors. RNA, whole genome sequencing and tandem mass tag proteomicsis completed and shared. Multiple brain regions including caudate, temporal and dorsolateral prefrontal cortex were profiled.

Interplay of education and DNA methylation age on cognitive impairment: insights from the Health and Retirement Study

Few studies have assessed the association of educational attainment on dementia and cognitive impairment through DNA methylation age acceleration, while accommodating exposure-mediator interaction effects. We evaluated the mediation role of six epigenetic clocks with dementia, cognitive impairment non-dementia, and normal cognition, while accommodating exposure-mediator interaction effects. To understand the joint association of low education (≤12 years) and DNA methylation age acceleration (yes/no) in relation to cognitive impairment, we used weighted logistic regression, adjusting for chronological age, sex, race/ethnicity, and cell type composition. We performed four-way mediation and interaction decomposition analysis. Analyses were conducted on 2016 venous blood study participants from the Health and Retirement Study (N = 3724). Both GrimAge acceleration (OR = 1.6 95%CI 1.3-2.1) and low educational attainment (OR = 2.4 95%CI 1.9-3.0) were associated with higher odds of cognitive impairment in a mutually adjusted logistic model. We found additive interaction associations between low education and GrimAge acceleration on dementia. We observed that 6-8% of the association of education on dementia was mediated through GrimAge acceleration. While mediation effects were small, the portion of the association of education on dementia due to additive interaction with GrimAge acceleration was between 23.6 and 29.2%. These results support the interplay of social disadvantage and biological aging processes on impaired cognition.

Hormone Therapy and Biological Aging in Postmenopausal Women

Importance

Menopause is associated with biological aging, and hormone therapy (HT) is associated with health outcomes in postmenopausal women.

Objective

To evaluate the association between HT use and discrepancies between chronological and biological age in postmenopausal women as well as the potential modifying role of socioeconomic status (SES).

Design, Setting, and Participants

This population-based, retrospective cohort study included postmenopausal women registered in the UK Biobank. A baseline survey on HT use and biological aging biomarkers was conducted from March 2006 to October 2010. Data analyses were conducted in December 2023.

Exposures

Information regarding HT use, the age at starting HT, and HT duration was collected via a touchscreen questionnaire. SES was evaluated by education, family income, occupation, and the Townsend Deprivation Index.

Main Outcomes and Measures

Biological aging discrepancy was evaluated using validated phenotypic age, which was calculated using chronological age and 9 biomarkers measured at baseline. All-cause and cause-specific mortality were also assessed.

Results

Among the 117 763 postmenopausal women (mean [SD] age, 60.2 [5.4] years), 47 461 (40.3%) ever used HT. The mean phenotypic age was 52.1 (7.9) years. Ever use of HT was associated with a smaller biological aging discrepancy than never use of HT (β, -0.17 years; 95% CI, -0.23 to -0.10 years). This smaller aging discrepancy was more evident in those who started HT at age 55 years or older (β, -0.32 years; 95% CI, -0.48 to -0.15 years) and in those who used HT for 4 to 8 years (β, -0.25 years; 95% CI, -0.35 to -0.15 years). The association between HT and a smaller aging discrepancy was more evident in women with low SES, with a significant interaction observed for education (higher education: β, -0.08 years [95% CI, -0.17 to 0.01]; other education: β, -0.23 [95% CI, -0.32 to -0.14] years; P for interaction = .02). Phenotypic aging discrepancy mediated 12.7% (95% CI, 6.3% to 23.9%) of the association between HT and all-cause mortality and cause-specific mortality.

Conclusions and Relevance

In this study, postmenopausal women with historical HT use were biologically younger than those not receiving HT, with a more evident association observed in those with low SES. The biological aging discrepancy mediated the association between HT and decreased mortality. Promoting HT in postmenopausal women could be important for healthy aging.

The pace of biological aging significantly mediates the relationship between internalized stigma of chronic pain and chronic low back pain severity among non-hispanic black but not non-hispanic white adults

This study aimed to determine the nature of the relationship between the internalized stigma of chronic pain (ISCP), the pace of biological aging, and racial disparities in nonspecific chronic low back pain (CLBP). We used Dunedin Pace of Aging from the Epigenome (DunedinPACE), Horvath's, Hannum's, and PhenoAge clocks to determine the pace of biological aging in adults, ages 18 to 82 years: 74 no pain, 56 low-impact pain, and 76 high-impact pain. Individuals with high-impact pain reported higher levels of ISCP and DunedinPACE compared to those with low-impact or no pain (p < 0.001). There was no significant relationship between ISCP and epigenetic age acceleration from Horvath, Hannum, and PhenoAge clocks (p > 0.05). Mediation analysis showed that an association between ISCP and pain severity and interference was mediated by the pace of biological aging (p ≤ 0.001). We further found that race moderated the indirect effect of ISCP on pain severity and interference, with ISCP being a stronger positive predictor of the pace of biological aging for non-Hispanic Blacks (NHBs) than for non-Hispanic Whites (NHWs). Future bio-behavioral interventions targeting internalized stigma surrounding chronic pain at various levels are necessary. A deeper understanding of the biological aging process could lead to improvements in managing nonspecific chronic low back pain (CLBP), particularly within underserved minority populations.

Accelerated Pace of Aging in Schizophrenia: Five Case-Control Studies

BACKGROUND

Schizophrenia is associated with increased risk of developing multiple aging-related diseases, including metabolic, respiratory, and cardiovascular diseases, and Alzheimer's and related dementias, leading to the hypothesis that schizophrenia is accompanied by accelerated biological aging. This has been difficult to test because there is no widely accepted measure of biological aging. Epigenetic clocks are promising algorithms that are used to calculate biological age on the basis of information from combined cytosine-phosphate-guanine sites (CpGs) across the genome, but they have yielded inconsistent and often negative results about the association between schizophrenia and accelerated aging. Here, we tested the schizophrenia-aging hypothesis using a DNA methylation measure that is uniquely designed to predict an individual's rate of aging.

METHODS

We brought together 5 case-control datasets to calculate DunedinPACE (Pace of Aging Calculated from the Epigenome), a new measure trained on longitudinal data to detect differences between people in their pace of aging over time. Data were available from 1812 psychosis cases (schizophrenia or first-episode psychosis) and 1753 controls. Mean chronological age was 38.9 (SD = 13.6) years.

RESULTS

We observed consistent associations across datasets between schizophrenia and accelerated aging as measured by DunedinPACE. These associations were not attributable to tobacco smoking or clozapine medication.

CONCLUSIONS

Schizophrenia is accompanied by accelerated biological aging by midlife. This may explain the wide-ranging risk among people with schizophrenia for developing multiple different age-related physical diseases, including metabolic, respiratory, and cardiovascular diseases, and dementia. Measures of biological aging could prove valuable for assessing patients' risk for physical and cognitive decline and for evaluating intervention effectiveness.

Bridging the Gap: Multi-Omics Profiling of Brain Tissue in Alzheimer's Disease and Older Controls in Multi-Ethnic Populations

INTRODUCTION

Multi-omics studies in Alzheimer's disease (AD) revealed many potential disease pathways and therapeutic targets. Despite their promise of precision medicine, these studies lacked African Americans (AA) and Latin Americans (LA), who are disproportionately affected by AD.

METHODS

To bridge this gap, Accelerating Medicines Partnership in AD (AMP-AD) expanded brain multi-omics profiling to multi-ethnic donors.

RESULTS

We generated multi-omics data and curated and harmonized phenotypic data from AA (n=306), LA (n=326), or AA and LA (n=4) brain donors plus Non-Hispanic White (n=252) and other (n=20) ethnic groups, to establish a foundational dataset enriched for AA and LA participants. This study describes the data available to the research community, including transcriptome from three brain regions, whole genome sequence, and proteome measures.

DISCUSSION

Inclusion of traditionally underrepresented groups in multi-omics studies is essential to discover the full spectrum of precision medicine targets that will be pertinent to all populations affected with AD.

Longitudinal study of traumatic-stress related cellular and cognitive aging

Traumatic stress is associated with both accelerated epigenetic age and increased risk for dementia. Accelerated epigenetic age might link symptoms of traumatic stress to dementia-associated biomarkers, such as amyloid-beta (Aβ) proteins, neurofilament light (NFL), and inflammatory molecules. We tested this hypothesis using longitudinal data obtained from 214 trauma-exposed military veterans (85 % male, mean age at baseline: 53 years, 75 % White) who were assessed twice over the course of an average of 5.6 years. Cross-lagged panel mediation models evaluated measures of lifetime posttraumatic stress disorder and internalizing and externalizing comorbidity (assessed at Time 1; T1) in association with T1 epigenetic age (per the GrimAge algorithm) and T1 plasma markers of neuropathology along with bidirectional temporal paths between T1 and T2 epigenetic age and the plasma markers. Results revealed that a measure of externalizing comorbidity was associated with accelerated epigenetic age (β = 0.30, p <.01), which in turn, was associated with subsequent increases in Aβ-40 (β = 0.20, p <.001), Aβ-42 (β = 0.18, p <.001), and interleukin-6 (β = 0.18, p <.01). T1 advanced epigenetic age and the T1 neuropathology biomarkers NFL and glial fibrillary acidic protein predicted worse performance on T2 neurocognitive tasks assessing working memory, executive/attentional control, and/or verbal memory (ps = 0.03 to 0.009). Results suggest that advanced GrimAge is predictive of subsequent increases in neuropathology and inflammatory biomarkers as well as worse cognitive function, highlighting the clinical significance of this biomarker with respect to cognitive aging and brain health over time. The finding that advanced GrimAge mediated the association between psychiatric comorbidity and future neuropathology is important for understanding potential pathways to neurodegeneration and early identification of those at greatest risk.

Daytime napping, biological aging and cognitive function among middle-aged and older Chinese: insights from the China health and retirement longitudinal study

Objective

The complicated association of daytime napping, biological aging and cognitive function remains inconclusive. We aimed to evaluate the cross-sectional and longitudinal associations of daytime napping and two aging measures with cognition and to examine whether napping affects cognition through a more advanced state of aging.

Methods

Data was collected from the China Health and Retirement Longitudinal Study. Napping was self-reported. We calculated two published biological aging measures: Klemera and Doubal biological age (KDM-BA) and physiological dysregulation (PD), which derived information from clinical biomarkers. Cognitive z-scores were calculated at each wave. Linear mixed models were used to explore the longitudinal association between napping, two aging measures, and cognitive decline. Mediation analyses were performed to assess the mediating effects of biological age acceleration on the association between napping and cognition.

Results

Participants aged over 45 years were included in the analyses. Non-nappers had greater KDM-BA and PD [LS means (LSM) = 0.255, p = 0.007; LSM = 0.085, p = 0.011] and faster cognitive decline (LSM = -0.061, p = 0.005)compared to moderate nappers (30-90 min/nap). KDM-BA (β = -0.007, p = 0.018) and PD (β = -0.034, p < 0.001) showed a negative association with overall cognitive z scores. KDM-BA and PD partially mediated the effect of napping on cognition.

Conclusion

In middle-aged and older Chinese, compared to moderate nappers, non-nappers seem to experience a more advanced state of aging and increased rates of cognitive decline. The aging status possibly mediates the association between napping and cognition. Moderate napping shows promise in promoting healthy aging and reducing the burden of cognitive decline in Chinese middle-aged and older adults.

Discordant Biological and Chronological Age: Implications for Cognitive Decline and Frailty

BACKGROUND

Older adults with discordant biological and chronological ages (BA and CA) may vary in cognitive and physical function from those with concordant BA and CA.

METHODS

To make our approach clinically accessible, we created easy-to-interpret participant groups in the Health, Aging, and Body Composition Study (N = 2 458, 52% female participants, 65% White participants, age: 73.5 ± 2.8) based on medians of CA, and a previously validated BA index comprised of readily available clinical tests. Joint models estimated associations of BA-CA group with cognition (Modified Mini-Mental State Examination [3MS] and Digit Symbol Substitution Test [DSST]) and frailty over 10 years.

RESULTS

The sample included the following: 32%, Young group (BA and CA < median); 21%, Prematurely Aging group (BA ≥ median, CA < median), 27%, Old group (BA and CA ≥ median), and 20%, Resilient group (BA < median, CA ≥ median). In education-adjusted models of cognition, among those with CA < median, the Prematurely Aging group performed worse than the Young at baseline (3MS and DSST p < .0001), but among those with CA ≥ median, the Resilient group did not outperform the Old group (3MS p = .31; DSST p = .25). For frailty, the Prematurely Aging group performed worse than the Young group at baseline (p = .0001), and the Resilient group outperformed the Old group (p = .003). For all outcomes, groups did not differ on change over time based on the same pairwise comparisons (p ≥ .40).

CONCLUSIONS

Discordant BA and CA identify groups who have greater cognitive and physical functional decline or are more protected than their CA would suggest. This information can be used for risk stratification.

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.

Biomarkers of aging for the identification and evaluation of longevity interventions

With the rapid expansion of aging biology research, the identification and evaluation of longevity interventions in humans have become key goals of this field. Biomarkers of aging are critically important tools in achieving these objectives over realistic time frames. However, the current lack of standards and consensus on the properties of a reliable aging biomarker hinders their further development and validation for clinical applications. Here, we advance a framework for the terminology and characterization of biomarkers of aging, including classification and potential clinical use cases. We discuss validation steps and highlight ongoing challenges as potential areas in need of future research. This framework sets the stage for the development of valid biomarkers of aging and their ultimate utilization in clinical trials and practice.

The structural and social determinants of Alzheimer's disease related dementias

INTRODUCTION

The projected growth of Alzheimer's disease (AD) and AD-related dementia (ADRD) cases by midcentury has expanded the research field and impelled new lines of inquiry into structural and social determinants of health (S/SDOH) as fundamental drivers of disparities in AD/ADRD.

METHODS

In this review, we employ Bronfenbrenner's ecological systems theory as a framework to posit how S/SDOH impact AD/ADRD risk and outcomes.

RESULTS

Bronfenbrenner defined the "macrosystem" as the realm of power (structural) systems that drive S/SDOH and that are the root cause of health disparities. These root causes have been discussed little to date in relation to AD/ADRD, and thus, macrosystem influences, such as racism, classism, sexism, and homophobia, are the emphasis in this paper.

DISCUSSION

Under Bronfenbrenner's macrosystem framework, we highlight key quantitative and qualitative studies linking S/SDOH with AD/ADRD, identify scientific gaps in the literature, and propose guidance for future research.

HIGHLIGHTS

Ecological systems theory links structural/social determinants to AD/ADRD. Structural/social determinants accrue and interact over the life course to impact AD/ADRD. Macrosystem is made up of societal norms, beliefs, values, and practices (e.g., laws). Most macro-level determinants have been understudied in the AD/ADRD literature.

Ranking the risk factors for Alzheimer's disease; findings from the UK Biobank study

Background

The cause of the most common form of dementia, sporadic Alzheimer's disease (AD), remains unknown. This may reflect insufficiently powered studies to date for this multi-factorial disorder. The UK Biobank dataset presents a unique opportunity to rank known risk factors and determine novel variables.

Methods

A custom machine learning approach for high dimensionality data was applied to explore prospectively associations between AD in a sub-cohort of 156,209 UK Biobank participants aged 60-70 including more than 2,090 who were subsequently diagnosed with AD.

Results

After the possession of the APOE4 allele, the next highest ranked risk factors were other genetic variants within the TOMM40-APOE-APOC1 locus. When stratified by their apolipoprotein epsilon 4 (APOE4) carrier status, the most prominent risk factors in carriers were AST:ALT ratio, the "number of treatments/ medications" taken as well as "time spent in hospital" while protection was conferred by "Sleeplessness/Insomnia". In non-APOE carriers, lower socioeconomic status and fewer years of education were highly ranked but effect sizes were small relative to APOE4 carriers.

Conclusions

Possession of the APOE4 allele was confirmed as the most important risk factor in AD. Other TOMM40-APOE-APOC1 locus variants further moderate the risk of AD in APOE4 carriers. Liver pathology is a novel risk factor in APOE4 carriers while "Sleeplessness/Insomnia" is protective in AD irrespective of APOE4 status. Other factors such as "Number of treatments/ medications" suggest that multimorbidity is an important risk factor for AD. Future treatments aimed at co-morbidities, including liver disease, may concomitantly lower the risk of sporadic AD.

Biomarkers of aging through the life course: A Recent Literature Update

Purpose of review

The development of biomarkers of aging has greatly advanced epidemiological studies of aging processes. However, much debate remains on the timing of aging onset and the causal relevance of these biomarkers. In this review, we discuss the most recent biomarkers of aging that have been applied across the life course.

Recent findings

The most recently developed aging biomarkers that have been applied across the life course can be designated into three categories: epigenetic clocks, epigenetic markers of chronic inflammation, and mitochondrial DNA copy number. While these have been applied at different life stages, the development, validation, and application of these markers has been largely centered on populations of older adults. Few studies have examined trajectories of aging biomarkers across the life course. As the wealth of molecular and biochemical data increases, emerging biomarkers may be able to capture complex and system-specific aging processes. Recently developed biomarkers include novel epigenetic clocks; clocks based on ribosomal DNA, transcriptomic profiles, proteomics, metabolomics, and inflammatory markers; clonal hematopoiesis of indeterminate potential gene mutations; and multi-omics approaches.

Summary

Attention should be placed on aging at early and middle life stages to better understand trajectories of aging biomarkers across the life course. Additionally, novel biomarkers will provide greater insight into aging processes. The specific mechanisms of aging reflected by these biomarkers should be considered when interpreting results.

Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status

Introduction

Despite the association of vitamin D deficiency with incident dementia, the role of supplementation is unclear. We prospectively explored associations between vitamin D supplementation and incident dementia in 12,388 dementia-free persons from the National Alzheimer's Coordinating Center.

Methods

Baseline exposure to vitamin D was considered D+; no exposure prior to dementia onset was considered D-. Kaplan-Meier curves compared dementia-free survival between groups. Cox models assessed dementia incidence rates across groups, adjusted for age, sex, education, race, cognitive diagnosis, depression, and apolipoprotein E (APOE) ε4. Sensitivity analyses examined incidence rates for each vitamin D formulation. Potential interactions between exposure and model covariates were explored.

Results

Across all formulations, vitamin D exposure was associated with significantly longer dementia-free survival and lower dementia incidence rate than no exposure (hazard ratio = 0.60, 95% confidence interval: 0.55-0.65). The effect of vitamin D on incidence rate differed significantly across the strata of sex, cognitive status, and APOE ε4 status.

Discussion

Vitamin D may be a potential agent for dementia prevention.

Highlights

In a prospective cohort study, we assessed effects of Vitamin D on dementia incidence in 12,388 participants from the National Alzheimer's Coordinating Center dataset.Vitamin D exposure was associated with 40% lower dementia incidence versus no exposure.Vitamin D effects were significantly greater in females versus males and in normal cognition versus mild cognitive impairment.Vitamin D effects were significantly greater in apolipoprotein E ε4 non-carriers versus carriers.Vitamin D has potential for dementia prevention, especially in the high-risk strata.