Epigenetic Aging and Racialized, Economic, and Environmental Injustice: NIMHD Social Epigenomics Program

Social determinants of health and epigenetic clocks: Meta-analysis of 140 studies

Social determinants of health are social factors that affect health and survival. Two of the most powerful social determinants are socioeconomic status (SES) and race/ethnicity; people with lower SES or marginalized race/ethnicity tend to experience earlier onset of aging-related diseases and have shorter lifespans. DNA methylation (DNAm) measures of biological aging, often referred to as "epigenetic clocks", are increasingly used to study the social determination of health. However, there are several generations of epigenetic clocks and it remains unclear which are most sensitive to social factors affecting health. Moreover, there is uncertainty about how technical factors, such as the tissue from which DNA is derived or the technology used to measure DNA methylation may affect associations of social determinants with epigenetic clocks. We conducted a pre-registered multi-level meta-analysis of 140 studies, including N = 65,919 participants, encompassing 1,065 effect sizes for associations of SES and racial/ethnic identity with three generations of epigenetic clocks. We found that associations were weakest for the first generation of epigenetic clocks developed to predict age differences between people. Associations were stronger for the second generation of epigenetic clocks developed to predict mortality and health risks. The strongest associations were observed for a third generation of epigenetic clocks, sometimes referred to as "epigenetic speedometers", developed to predict the pace of aging. In studies of children, only the speedometers showed significant associations with SES. Effects of sex and technical factors were minimal and there was no evidence of publication bias.

Analyzing structural racism and its health impacts: it's about time

It's about time. Since 2020, new work on structural racism and health has erupted in the United States, with 93% of the 1655 PubMed articles indexed by "structural racism" as of April 4, 2024 having been published during or since 2020. Among the 310 review articles included, most have focused either on improving conceptual, substantive, and methodologic clarity and precision about measuring and modeling structural racism, or reviewing evidence about its impacts on specific exposures or outcomes. However, only 2.5% of these 1655 articles are also indexed by the term "lifecourse" and its variants, and among the reviews considered here, none explicitly discuss issues involving etiologic period. Informed by ecosocial theory's temporal theorizing about pathways of embodiment, and also Latin American social medicine-collective health framings of "health-illness-disease processes," lifecourse models, and the construct of the "cancer control continuum," in this brief commentary I consider how time matters in relation to concrete examples involving structural racism and cancer and also inconsistent results reported by several studies using latent measures of structural racism. When it comes to structural racism and health, it truly is about time-and it is time for this work to tackle issues of time.

Pubertal timing as a predictor of epigenetic aging and mortality risk in young adulthood

Early pubertal timing is associated with adverse health in adulthood. These effects may be mediated by DNA methylation changes associated with accelerated cellular aging and mortality risk, but few studies tested associations between pubertal timing and epigenetic markers in adulthood. Additionally, pubertal timing effects often vary by sex and are understudied in diverse youth. Thus, this longitudinal study examined links between pubertal timing and later epigenetic aging and mortality risk together with sex differences in predominantly Black youth. Participants included 350 individuals (58% female, 42% male; 80% Black, 19% non-Hispanic White). Perceived pubertal timing relative to peers and self-reported phenotypic pubertal timing based on age-adjusted Tanner scores were assessed during early adolescence (Mage = 13) whereas epigenetic aging (GrimAge, DunedinPace of Aging Calculated from the Epigenome, and PhenoAge) and mortality risk were measured during young adulthood (Mage = 27). After adjusting for covariates (smoking, body mass index, family income, early-life stress, race/ethnicity, sex, parenthood), early pubertal timing (both perceived and phenotypic) predicted higher epigenetic mortality risk, and early phenotypic pubertal timing predicted accelerated DunedinPace of Aging Calculated from the Epigenome. Both perceived and phenotypic early pubertal timing were correlated with accelerated GrimAge. Off-time phenotypic pubertal timing (i.e., early and late) was associated with accelerated PhenoAge in males only whereas perceived off-time pubertal timing was unexpectedly linked with lower PhenoAge acceleration. These findings extend prior research by linking two dimensions of early pubertal timing with epigenetic mortality risk and accelerated aging in racially diverse young adults and showing nonlinear effects on PhenoAge acceleration that differ across pubertal timing measures and show some sex differences. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Analyzing multiple types of discrimination using implicit and explicit measures, comparing target vs. Dominant groups, in a study of smoking/vaping among community health center members in Boston, Massachusetts (2020-2022)

BACKGROUND

In the United States (U.S.), the physical and mental health sequelae of diverse types of discrimination are far-reaching, severe, and contribute to population health inequities, with this work informing research on discrimination and health in both the Global North and Global South. To date, limited population health research has examined the joint impacts of discrimination measures that are explicit (i.e., self-report) and implicit (i.e., automatic mental representations), both singly and for multiple types of discrimination.

METHODS

Between May 28, 2020-August 4, 2022, we conducted Life + Health, a cross-sectional population-based study regarding six types of discrimination-racism, sexism, heterosexism, cissexism, ageism, and sizeism-with 699 participants (US-born, ages 25-64) from three community health centers in Boston, Massachusetts. Participants completed a Brief Implicit Association Test (B-IAT) and self-reported survey. Spearman's correlation coefficient was estimated to assess the strength and direction of discrimination types across target/dominant groups; logistic regression models were fit to assess the association of each type of discrimination with smoking/vaping following by random-effects meta-regression modeling to pool effects across discrimination types.

RESULTS

Mean age was 37.9 years (SD = 11.2 years). Overall, 31.6% were people of color; 31.8% identified as transgender or nonbinary/genderqueer; 68.6% were sexual minority. For education, 20.5% had some college/vocational school or no college. Current cigarette/vaping was reported by 15.4% of the study population. Implicit and explicit measures were generally correlated with one another, but associations varied across discrimination types and for target/dominant groups. In random-effects meta-regression modeling, explicit compared to implicit discrimination measures were associated with a 1.18 (95% CI = 1.00-1.39) greater odds of smoking/vaping among dominant group members, but no such difference was observed among target group members.

CONCLUSION

Implicit and explicit discrimination measures yielded distinct yet complementary insights, highlighting the importance of both. Meta-regression provided evidence of health impacts across discrimination types. Future research on discrimination and health, in diverse country contexts, should consider using both implicit and explicit measures to analyze health impacts across multiple types of discrimination.

Linked emergence of racial disparities in mental health and epigenetic biological aging across childhood and adolescence

Marginalization due to structural racism may confer an increased risk for aging-related diseases - in part - via effects on people's mental health. Here we leverage a prospective birth cohort study to examine whether the emergence of racial disparities in mental health and DNA-methylation measures of biological aging (i.e., DunedinPACE, GrimAge Acceleration, PhenoAge Acceleration) are linked across childhood and adolescence. We further consider to what extent racial disparities are statistically accounted for by perinatal and postnatal factors in preregistered analyses of 4898 participants from the Future of Families & Child Wellbeing Study, of which 2039 had repeated saliva DNA methylation at ages 9 and 15 years. We find that racially marginalized children had higher levels of externalizing and internalizing behaviors and diverging longitudinal internalizing slopes. Black compared to White identifying children, children living in more racially segregated neighborhoods, and racially marginalized children more affected by colorism tended to have higher age-9 levels of biological aging and more biological age acceleration over adolescence. Notably, longitudinal increases in internalizing and externalizing behavior were correlated with increases in biological aging. While racial and ethnic disparities in mental health were largely statistically accounted for by socioeconomic variables, differences in biological aging were often still visible after including potential mediating variables. These findings underscore the urgency for future research to consider biological aging processes from early life and collect more comprehensive measures of structural racism in developmental cohorts. Programs dedicated to advancing racial health equity must address the psychological and physical effects of structural racism on children and adolescents.

Diversity in women and their vaginal microbiota

Women's health is essential to global societal and economic wellbeing, yet health disparities remain prevalent. The vaginal microbiota plays a critical role in health, with research indicating that reduced levels of core bacteria, such as lactobacilli, are associated with conditions like bacterial vaginosis (BV) and increased infection susceptibility. Lower levels of vaginal lactobacilli are reported more frequently in women of African and Latin American descent compared with women of European and Asian descent. However, geographical and other study inclusion and analysis biases influence current research. This opinion highlights the need for a more comprehensive understanding of a 'healthy' vaginal microbiome. It underscores efforts to broaden global research on microbiome diversity in socially relevant contexts, avoiding inappropriate applications of terms such as race and ethnicity.

Community Threat, Positive Parenting, and Accelerated Epigenetic Aging: Longitudinal Links from Childhood to Adolescence

Early Life Adversity (ELA) has been linked to accelerated epigenetic aging. While positive parenting is hypothesized to buffer the detrimental effects of ELA on child development, its role in mitigating epigenetic age acceleration remains unclear. Data from 2,039 children (49.7% female) in the Future of Families and Child Wellbeing Study (FFCWS) were included in the current study (46.7% Black, 26.5% Hispanic, 19% White non-Hispanic). Home and community threat and observed parenting were measured from ages 3 to 9. Salivary epigenetic age acceleration was measured at ages 9 and 15. Positive parenting reduces the pace of epigenetic aging in low, but not high, community-threat environments. Interventions across home and community environments may be necessary to prevent ELA's biological embedding.

Climate geroscience: the case for 'wisdom-inquiry' science

Why should, and how can, the fields of climate science and geroscience (which studies the biology of ageing) facilitate the cross-disciplinary collaboration needed to ensure that human and planetary health are both promoted in the future of an older, and warmer, world? Appealing to the ideal of 'wisdom-oriented' science (Maxwell 1984 In From knowledge to wisdom: a revolution in the aims and methods of science), where scientists consider themselves to be artisans working for the public good, a number of the real-world epistemic constraints on the scientific enterprise are identified. These include communicative frames that stoke intergenerational conflict (rather than solidarity) and treat the ends of planetary and human health as independent 'sacred values' (Tetlock 2003 Trends Cogn. Sci. 7, 320-324) rather than as interdependent ends. To foster 'climate geroscience'-the field of knowledge and translational science at the intersection of climate science and geroscience-researchers in both fields are encouraged to think of novel ways they could make researchers from the other field 'conversationally' present when framing the aspirations of their respective fields, applying for grant funding and designing their conferences and managing their scientific journals.

Methylation Clocks Do Not Predict Age or Alzheimer's Disease Risk Across Genetically Admixed Individuals

Epigenetic clocks that quantify rates of aging from DNA methylation patterns across the genome have emerged as a potential biomarker for risk of age-related diseases, like Alzheimer's disease (AD), and environmental and social stressors. However, methylation clocks have not been validated in genetically diverse cohorts. Here we evaluate a set of methylation clocks in 621 AD patients and matched controls from African American, Hispanic, and white cohorts. The clocks are less accurate at predicting age in genetically admixed individuals, especially those with substantial African ancestry, than in the white cohort. The clocks also do not consistently identify age acceleration in admixed AD cases compared to controls. Methylation QTL (meQTL) commonly influence CpGs in clocks, and these meQTL have significantly higher frequencies in African genetic ancestries. Our results demonstrate that methylation clocks often fail to predict age and AD risk beyond their training populations and suggest avenues for improving their portability.

Common DNA sequence variation influences epigenetic aging in African populations

Aging is associated with genome-wide changes in DNA methylation in humans, facilitating the development of epigenetic age prediction models. However, most of these models have been trained primarily on European-ancestry individuals, and none account for the impact of methylation quantitative trait loci (meQTL). To address these gaps, we analyzed the relationships between age, genotype, and CpG methylation in 3 understudied populations: central African Baka (n = 35), southern African ‡Khomani San (n = 52), and southern African Himba (n = 51). We find that published prediction methods yield higher mean errors in these cohorts compared to European-ancestry individuals, and find that unaccounted-for DNA sequence variation may be a significant factor underlying this loss of accuracy. We leverage information about the associations between DNA genotype and CpG methylation to develop an age predictor that is minimally influenced by meQTL, and show that this model remains accurate across a broad range of genetic backgrounds. Intriguingly, we also find that the older individuals and those exhibiting relatively lower epigenetic age acceleration in our cohorts tend to carry more epigenetic age-reducing genetic variants, suggesting a novel mechanism by which heritable factors can influence longevity.

Advancing Health Disparities Science Through Social Epigenomics Research

Importance

Although scientific and technological discoveries have improved the health of the US population overall, racial and ethnic minority (American Indian and Alaska Native, Asian, Black or African American, Hispanic or Latino, or Native Hawaiian and Pacific Islander persons) and socioeconomically disadvantaged populations continue to experience a disproportionate burden of disease and other adverse health conditions. To better understand and address the drivers of health disparities and inform the development of effective interventions, integrative mechanistic studies examining the dynamic interplay of multiple factors across the life course and even between generations are needed. The emerging field of social epigenomics, which seeks to link social stressors and protective factors to health status through the examination of epigenomic modifications of various biological pathways, is one promising area of research contributing to this need.

Observations

This thematic issue of JAMA Network Open highlights new findings from the grantees of the National Institutes of Health (NIH) Social Epigenomics Program. These findings, taken together, examine the associations of a variety of social, behavioral, and structural factors throughout the life course with epigenomic and other biological changes among populations experiencing health disparities. The studies link early-life exposures, structural inequities, and behavioral factors and interventions to epigenetic changes, and in some studies, later health outcomes. While there is still more work to be done to fully characterize the mechanistic pathways linking social exposures to epigenetic changes and health outcomes, the body of work presented in this special issue represents solid progress toward this goal.

Conclusions and Relevance

The studies highlighted in this special issue demonstrate important scientific progress in the complex integration of social determinants of health and health disparities with biological pathways and health outcomes to improve understanding of the mechanisms underlying health disparities among various underserved populations. Continued progress remains important in integrating different disciplines to transform the field of health disparities research.