DNA Methylation "GrimAge" Acceleration Mediates Sex/Gender Differences in Verbal Memory and Processing Speed: Findings From the Health and Retirement Study

How much can biomarkers explain sociodemographic inequalities in cognitive dysfunction and cognitive impairment? Results from a machine learning model in the Health and Retirement Study

BackgroundBiomarkers may be pathways by which social adversity affects cognitive aging and Alzheimer's disease and related dementias (ADRD) risk.ObjectiveHow much variance in cognitive dysfunction and cognitive impairment onset do blood-based and physiological biomarkers provide above and beyond easily attainable sociodemographic variables, and how much can biomarkers explain differences in cognitive functioning and ADRD by sociodemographic variables?MethodsWe utilize machine learning to generate measures of predicted cognitive dysfunction and cognitive impairment incidence based on 91 biomarkers, identify the relative importance of each biomarker, and examine how much these biomarkers mediate sociodemographic differences.ResultsMarkers related to cellular aging, neurodegeneration, diet and nutrition, immune functioning, and lung function were identified as important. Biomarkers mediated 47.2-77.3% of the variance associated with age, 22.7-35.2% of racial/ethnic differences in cognitive dysfunction, and 12.5-17.6% of educational differences.ConclusionsBiomarkers provide the potential to understand pathways linking sociodemographic characteristics to cognitive functioning and health. Future research should consider additional biomarkers and evaluate the specific systems that put people at risk for cognitive impairment.

Sex-specific mechanisms in vascular aging: exploring cellular and molecular pathways in the pathogenesis of age-related cardiovascular and cerebrovascular diseases

Aging remains the foremost risk factor for cardiovascular and cerebrovascular diseases, surpassing traditional factors in epidemiological significance. This review elucidates the cellular and molecular mechanisms underlying vascular aging, with an emphasis on sex differences that influence disease progression and clinical outcomes in older adults. We discuss the convergence of aging processes at the macro- and microvascular levels and their contributions to the pathogenesis of vascular diseases. Critical analysis of both preclinical and clinical studies reveals significant sex-specific variations in these mechanisms, which could be pivotal in understanding the disparity in disease morbidity and mortality between sexes. The review highlights key molecular pathways, including oxidative stress, inflammation, and autophagy, and their differential roles in the vascular aging of males and females. We argue that recognizing these sex-specific differences is crucial for developing targeted therapeutic strategies aimed at preventing and managing age-related vascular pathologies. The implications for personalized medicine and potential areas for future research are also explored, emphasizing the need for a nuanced approach to the study and treatment of vascular aging.

Characterising and differentiating cognitive and motor speed in older adults: structural equation modelling on a UK longitudinal birth cohort

OBJECTIVES

Information processing speed (IPS) has been proposed to be a key component in healthy ageing and cognitive functioning. Yet, current studies lack a consistent definition and specific influential characteristics. This study aimed to investigate IPS as a multifaceted concept by differentiating cognitive and motor IPS.

DESIGN, SETTING AND PARTICIPANTS

A retrospective data analysis using data from the Medical Research Council National Survey of Health and Development (a population-based cohort of UK adults born in 1946) at childhood (ages 8, 11 and 15) and adulthood (ages 60-64 and 68-70). Using structural equation modelling, we constructed two models of IPS with 2124 and 1776 participants, respectively.

OUTCOME MEASURES

Measures of interest included IPS (ie, letter cancellation, simple and choice reaction time), intelligence (ie, childhood intelligence and National Adult Reading Test), verbal memory, socioeconomic status (SES) and cognitive functions measured by the Addenbrooke's Cognitive Examination III, as well as a variety of health indexes.

RESULTS

We found distinct predictors for cognitive and motor IPS and how they relate to other cognitive functions in old age. In our first model, SES and antipsychotic medication usage emerged as significant predictors for cognitive IPS, intelligence and smoking as predictors for motor IPS while both share sex, memory and antiepileptic medication usage as common predictors. Notably, all differences between both IPS types ran in the same direction except for sex differences, with women performing better than men in cognitive IPS and vice versa in motor IPS. The second model showed that both IPS measures, as well as intelligence, memory, antipsychotic and sedative medication usage, explain cognitive functions later in life.

CONCLUSION

Taken together, these results shed further light on IPS as a whole by showing there are distinct types and that these measures directly relate to other cognitive functions.

Associations of childhood, adolescence, and midlife cognitive function with DNA methylation age acceleration in midlife

Prior studies showed increased age acceleration (AgeAccel) is associated with worse cognitive function among old adults. We examine the associations of childhood, adolescence and midlife cognition with AgeAccel based on DNA methylation (DNAm) in midlife. Data are from 359 participants who had cognition measured in childhood and adolescence in the Child Health and Development study, and had cognition, blood based DNAm measured during midlife in the Disparities study. Childhood cognition was measured by Raven's Progressive Matrices and Peabody Picture Vocabulary Test (PPVT). Adolescent cognition was measured only by PPVT. Midlife cognition included Wechsler Test of Adult Reading (WTAR), Verbal Fluency (VF), Digit Symbol (DS). AgeAccel measures including Horvath, Hannum, PhenoAge, GrimAge and DunedinPACE were calculated from DNAm. Linear regressions adjusted for potential confounders were utilized to examine the association between each cognitive measure in relation to each AgeAccel. There are no significant associations between childhood cognition and midlife AgeAccel. A 1-unit increase in adolescent PPVT, which measures crystalized intelligence, is associated with 0.048-year decrease of aging measured by GrimAge and this association is attenuated after adjustment for adult socioeconomic status. Midlife crystalized intelligence measure WTAR is negatively associated with PhenoAge and DunedinPACE, and midlife fluid intelligence measure (DS) is negatively associated with GrimAge, PhenoAge and DunedinPACE. AgeAccel is not associated with VF in midlife. In conclusion, our study showed the potential role of cognitive functions at younger ages in the process of biological aging. We also showed a potential relationship of both crystalized and fluid intelligence with aging acceleration.

Diet, Pace of Biological Aging, and Risk of Dementia in the Framingham Heart Study

OBJECTIVE

People who eat healthier diets are less likely to develop dementia, but the biological mechanism of this protection is not well understood. We tested the hypothesis that healthy diet protects against dementia because it slows the pace of biological aging.

METHODS

We analyzed Framingham Offspring Cohort data. We included participants ≥60 years-old, free of dementia and having dietary, epigenetic, and follow-up data. We assessed healthy diet as long-term adherence to the Mediterranean-Dash Intervention for Neurodegenerative Delay diet (MIND, over 4 visits spanning 1991-2008). We measured the pace of aging from blood DNA methylation data collected in 2005-2008 using the DunedinPACE epigenetic clock. Incident dementia and mortality were defined using study records compiled from 2005 to 2008 visit through 2018.

RESULTS

Of n = 1,644 included participants (mean age 69.6, 54% female), n = 140 developed dementia and n = 471 died over 14 years of follow-up. Greater MIND score was associated with slower DunedinPACE and reduced risks for dementia and mortality. Slower DunedinPACE was associated with reduced risks for dementia and mortality. In mediation analysis, slower DunedinPACE accounted for 27% of the diet-dementia association and 57% of the diet-mortality association.

INTERPRETATION

Findings suggest that slower pace of aging mediates part of the relationship of healthy diet with reduced dementia risk. Monitoring pace of aging may inform dementia prevention. However, a large fraction of the diet-dementia association remains unexplained and may reflect direct connections between diet and brain aging that do not overlap other organ systems. Investigation of brain-specific mechanisms in well-designed mediation studies is warranted. ANN NEUROL 2024;95:1069-1079.

Geroscience and pathology: a new frontier in understanding age-related diseases

Geroscience, a burgeoning discipline at the intersection of aging and disease, aims to unravel the intricate relationship between the aging process and pathogenesis of age-related diseases. This paper explores the pivotal role played by geroscience in reshaping our understanding of pathology, with a particular focus on age-related diseases. These diseases, spanning cardiovascular and cerebrovascular disorders, malignancies, and neurodegenerative conditions, significantly contribute to the morbidity and mortality of older individuals. We delve into the fundamental cellular and molecular mechanisms underpinning aging, including mitochondrial dysfunction and cellular senescence, and elucidate their profound implications for the pathogenesis of various age-related diseases. Emphasis is placed on the importance of assessing key biomarkers of aging and biological age within the realm of pathology. We also scrutinize the interplay between cellular senescence and cancer biology as a central area of focus, underscoring its paramount significance in contemporary pathological research. Moreover, we shed light on the integration of anti-aging interventions that target fundamental aging processes, such as senolytics, mitochondria-targeted treatments, and interventions that influence epigenetic regulation within the domain of pathology research. In conclusion, the integration of geroscience concepts into pathological research heralds a transformative paradigm shift in our understanding of disease pathogenesis and promises breakthroughs in disease prevention and treatment.

Epigenetics of the far northern Yakutian population

BACKGROUND

Yakuts are one of the indigenous populations of the subarctic and arctic territories of Siberia characterized by a continental subarctic climate with severe winters, with the regular January average temperature in the regional capital city of Yakutsk dipping below - 40 °C. The epigenetic mechanisms of adaptation to such ecologies and environments and, in particular, epigenetic age acceleration in the local population have not been studied before.

RESULTS

This work reports the first epigenetic study of the Yakutian population using whole-blood DNA methylation data, supplemented with the comparison to the residents of Central Russia. Gene set enrichment analysis revealed, among others, geographic region-specific differentially methylated regions associated with adaptation to climatic conditions (water consumption, digestive system regulation), aging processes (actin filament activity, cell fate), and both of them (channel activity, regulation of steroid and corticosteroid hormone secretion). Further, it is demonstrated that the epigenetic age acceleration of the Yakutian representatives is significantly higher than that of Central Russia counterparts. For both geographic regions, we showed that epigenetically males age faster than females, whereas no significant sex differences were found between the regions.

CONCLUSIONS

We performed the first study of the epigenetic data of the Yakutia cohort, paying special attention to region-specific features, aging processes, age acceleration, and sex specificity.

Diet, pace of biological aging, and risk of dementia in the Framingham Heart Study

INTRODUCTION

We tested the hypothesis that healthy diet protects against dementia because it slows the pace of biological aging.

METHODS

We analyzed Framingham Offspring Cohort data (≥60y). We measured healthy diet using the Dietary Guideline for Americans (DGA, 3 visits 1991-2008), pace of aging using the DunedinPACE epigenetic clock (2005-2008), and incident dementia and mortality using records (compiled 2005-2018).

RESULTS

Of n=1,525 included participants (mean age 69.7, 54% female), n=129 developed dementia and n=432 died over follow-up. Greater DGA adherence was associated with slower DunedinPACE and reduced risks for dementia and mortality. Slower DunedinPACE was associated with reduced risks for dementia and mortality. Slower DunedinPACE accounted for 15% of the DGA association with dementia and 39% of the DGA association with mortality.

DISCUSSION

Findings suggest that slower pace of aging mediates part of the relationship of healthy diet with reduced dementia risk. Monitoring pace of aging may inform dementia prevention.

A comparison of cognitive performances based on differing rates of DNA methylation GrimAge acceleration among older men and women

Cognitive heterogeneity increases with age rendering sex differences difficult to identify. Given established sex differences in biological aging, we examined whether comparisons of men and women on neuropsychological test performances differed as a function of age rate. Data were obtained from 1921 adults enrolled in the 2016 wave of the Health and Retirement Study. The residual from regressing the DNA methylation GrimAge clock on chronological age was used as the measure of aging rate. Slow and fast age rates were predefined as 1 standard deviation below or above the sex-specific mean rates, respectively. ANCOVAs were used to test group differences in test performances. Pairwise comparisons revealed that slow aging men outperformed fast aging women (and vice versa) on measures of executive function/speed, visual memory and semantic fluency; however, when groups were matched by aging rates, no significant differences remained. In contrast, women, regardless of their aging rates, education or depressive symptoms maintained their advantage on verbal learning and memory. Implications for research on sex differences in cognitive aging are discussed.

Female APOE ɛ4 Carriers with Slow Rates of Biological Aging Have Better Memory Performances Compared to Female ɛ4 Carriers with Accelerated Aging

BACKGROUND

Evidence suggests that APOE ɛ4 carriers have worse memory performances compared to APOE ɛ4 non-carriers and effects may vary by sex and age. Estimates of biological age, using DNA methylation may enhance understanding of the associations between sex and APOE ɛ4 on cognition.

OBJECTIVE

To investigate whether associations between APOE ɛ4 status and memory vary according to rates of biological aging, using a DNA methylation age biomarker, in older men and women without dementia.

METHODS

Data were obtained from 1,771 adults enrolled in the 2016 wave of the Health and Retirement Study. A series of ANCOVAs were used to test the interaction effects of APOE ɛ4 status and aging rates (defined as 1 standard deviation below (i.e., slow rate), or above (i.e., fast rate) their sex-specific mean rate of aging on a composite measure of verbal learning and memory.

RESULTS

APOE ɛ4 female carriers with slow rates of GrimAge had significantly better memory performances compared to fast and average aging APOE ɛ4 female carriers. There was no effect of aging group rate on memory in the female non-carriers and no significant differences in memory according to age rate in either male APOE ɛ4 carriers or non-carriers.

CONCLUSION

Slower rates of aging in female APOE ɛ4 carriers may buffer against the negative effects of the ɛ4 allele on memory. However, longitudinal studies with larger sample sizes are needed to evaluate risk of dementia/memory impairment based on rates of aging in female APOE ɛ4 carriers.