Anne K. Bozack’s research while affiliated with Palo Alto University and other places

Background DNA methylation-based predictors of phenotypic traits including leukocyte proportions, smoking activity, biological aging, and circulating levels of plasma proteins are widely used as biomarkers in public health research. However, limited racial and ethnic diversity of research participants is an ongoing issue for epigenetics research, and the potential downstream impacts of limited diversity in training samples on the performance of epigenetic predictors remains poorly understood. We examined the performance of epigenetic predictors of chronological age (also known as epigenetic clocks), telomere length, cell proportions, and plasma proteins within a diverse sample of adult NHANES participants during the 1999–2000 and 2001–2002 survey cycles, both overall and stratified by self-reported race/ethnicity and sex. We utilized correlation coefficients and median absolute errors (MAE) to judge predictor performance, and bootstrapping and multivariate regression to assess the significance of differences between groups. Results All epigenetic predictors were significantly associated with their corresponding phenotypic traits in the overall population, with particularly high correlations for the epigenetic clocks and cell proportion estimates. Several significant differences in performance were observed between racial/ethnic groups, particularly for the plasma protein predictors, with a reoccurring trend of lower correlation in Mexican American and non-Hispanic Black participants compared to non-Hispanic White participants. Sex-differences in performance for several predictors were also identified but were not as pronounced. Multivariate regression models indicated that disparities in epigenetic predictor performance persisted after accounting for overall differences in epigenetic predictions related to race/ethnicity and sex, as well as further adjustment for estimated cell proportions and SES variables. Conclusions We found evidence for substantial disparities in epigenetic predictor performance, with each predictor exhibiting at least one significant difference in correlation or MAE related to race, ethnicity, or sex.

Background: Immigrant status and citizenship influence health and well-being, yet their associations with DNA methylation (DNAm)-based biomarkers of aging - key predictors of healthspan and lifespan, also known as epigenetic aging - remain underexplored. Methods: Using a representative sample of 2,336 United States (U.S.) adults from the 1999-2000 and 2001-2002 cycles of the National Health and Nutrition Examination Survey (NHANES), we analyzed cross-sectional associations of immigrant status and U.S. citizenship with seven epigenetic aging biomarkers: HannumAge, HorvathAge, SkinBloodAge, PhenoAge, GrimAge2, DNAm Telomere Length, and DunedinPoAm. Results: After adjusting for demographic factors, immigrants had 2.53-year lower GrimAge2 measures (95%CI: -3.44, -1.63, p < 0.001) compared to non-immigrants. U.S. citizens had 1.98-year higher GrimAge2 measures (95%CI: 0.66, 3.30, p = 0.005) compared to non-citizens. The GrimAge2 associations with immigrant status (β = -1.04-years, 95%CI: -1.87, -0.21, p = 0.02) and citizenship (β = 1.35-years, 95%CI: 0.38, 2.32, p = 0.02) were attenuated after adjusting for other lifestyle/health variables. Immigrant status and citizenship were associated with estimated levels of several GrimAge2 DNAm component proteins, including adrenomedullin and C-reactive protein. Conclusion: Our results support the paradigm of the immigrant mortality advantage and highlight the potential value of epigenetic age measures in studying socioeconomic and broader factors influencing citizen and immigrant health.

Reproductive aging, including timing of menarche and menopause, influences long-term morbidity and mortality in women, yet underlying biological mechanisms remain poorly understood. Using DNA methylation-based biomarkers, we assessed associations of age at menarche (N = 1,033) and menopause (N = 658) with epigenetic aging in a nationally representative sample of women ≥ 50 years. Later age at menopause was associated with lower GrimAge epigenetic age deviation (B = − 0.10 years, 95% CI: − 0.19, − 0.02). No associations were observed for menarche timing. This suggests a connection between earlier menopause and biological aging, with potential clinical implications for identifying those at high risk for age-related disease.

Epigenetic clocks can serve as pivotal biomarkers linking environmental exposures with biological aging. However, research on the influence of environmental exposures on epigenetic aging has largely been limited to a small number of chemicals and specific populations. We harnessed data from the National Health and Nutrition Examination Survey 1999-2000 and 2001-2002 cycles to examine exposome-wide associations between environmental exposures and epigenetic aging. A total of 8 epigenetic aging biomarkers were obtained from whole blood in 2,346 participants ranging from 50-84 years of age. A total of 64 environmental exposures including phthalates, metals, pesticides, dioxins, and polychlorinated biphenyls (PCBs) were measured in blood and urine. Associations between log2-transformed/standardized exposure measures and epigenetic age acceleration (EAA) were assessed using survey-weighted generalized linear regression. A 1 standard deviation (SD) increase in log2 serum cadmium levels was associated with higher GrimAge acceleration (beta = 1.23 years, p = 3.63e-06), higher GrimAge2 acceleration (beta = 1.27 years, p = 1.62e-05), and higher DunedinPoAm (beta = 0.02, p = 2.34e-05). A 1 SD increase in log2 serum cotinine levels was associated with higher GrimAge2 acceleration (beta = 1.40 years, p = 6.53e-04) and higher DunedinPoAm (beta = 0.03, p = 6.31e-04). Associations between cadmium and EAA across several clocks persisted in sensitivity models adjusted for serum cotinine levels, and other associations involving lead, dioxins, and PCBs were identified. Several environmental exposures are associated with epigenetic aging in a nationally representative US adult population, with particularly strong associations related to cadmium and cotinine across several epigenetic clocks.

Long-term exposure to ambient air pollution has been associated with epigenetic age acceleration (EAA) in adults, but its impact on children remains less understood. This study analyzed data from 457 children (mean age: 7.9 years) in the Project Viva cohort (2007-2010, eastern Massachusetts, USA). We calculated EAA from leukocytes: Horvath’s Epigenetic Age Acceleration (HorvathEAA), Intrinsic Epigenetic Age Acceleration (IEAA), and Skin and Blood Epigenetic Age Acceleration (Skin&BloodEAA). We applied generalized additive models to evaluate associations of prior 365-day average and lifetime average exposure to PM2.5, NO2, and O3, and distance to major roadways with EAA. Results indicated that each interquartile range of prior 365-day average of PM2.5 corresponded with 0.26 years (95% CI: -0.49, -0.03) lower HorvathEAA, although it did not survive multiple testing adjustment. Similar patterns but with wider confidence intervals were observed for IEAA (-0.22, 95% CI: -0.44, 0.01) and Skin&BloodEAA (-0.04, 95% CI: -0.19, 0.11). No associations were observed of exposure to lifetime average PM2.5, prior-year or lifetime average NO2 or O3, or distance to major roadways with EAA. These findings suggest higher prior 365-day average PM2.5 exposure may relate to lower HorvathEAA in children.

Background: One-carbon metabolism (OCM), a biochemical pathway dependent on micronutrients including folate and vitamin B12, plays an essential role in aging-related physiological processes. DNA methylation-based aging biomarkers may be influenced by OCM. Objective: This study investigated associations of OCM-related biomarkers with epigenetic aging biomarkers in the National Health and Nutrition Examination Survey (NHANES). Methods: Blood DNA methylation was measured in adults aged greater or equal to 50 years in the 1999-2000 and 2001-2002 cycles of NHANES. The following epigenetic aging biomarkers were included: Horvath1, Horvath2, Hannum, PhenoAge, GrimAge2, DunedinPoAm, and DNA methylation telomere length (DNAmTL). We tested for associations of serum folate, red blood cell (RBC) folate, vitamin B12, homocysteine, and methylmalonic acid concentrations with epigenetic age deviation (EAD) among 2,346 participants with epigenetic and nutritional status biomarkers using survey weighted general linear regression models adjusting for sociodemographics, BMI, and behavioral factors. Results: A doubling of serum folate concentration was associated with -0.82 years (95% confidence interval (CI) = -1.40, -0.23) lower GrimAge EAD, -0.13 SDs (-0.22, -0.03) lower DunedinPoAm, and 0.02 kb (0.00, 0.04) greater DNAmTL EAD. Associations were attenuated after adjusting for smoking status and alcohol intake, folate antagonists. Conversely, a doubling in homocysteine concentration was associated with 1.05 years (0.06, 2.04) greater PhenoAge EAD, 1.93 years (1.16, 2.71) greater GrimAge2 EAD, and 0.26 SDs (0.10, 0.41) greater DunedinPoAm. Associations with GrimAge2 EAD and DunedinPoAm were robust to alcohol and smoking adjustment. Conclusions: In a nationally representative sample of U.S. adults, greater folate, a carbon donor, was associated with lower EAD, and greater homocysteine, an indicator of OCM deficiencies, was associated with greater EAD; however, some associations were influenced by smoking status. Future research should focus on high-risk populations. Randomized controlled trials with long-term follow-up are also needed to established causality and investigate the clinical relevance of changes in EAD.

Reproductive aging, including timing of menarche and menopause, influences long-term morbidity and mortality in women, yet underlying biological mechanisms remain poorly understood. Using DNA methylation-based biomarkers, we assessed associations of age at menarche (N=1,033) and menopause (N=658) with epigenetic aging in a nationally representative sample of women ≥50 years. Later age at menopause was associated with lower GrimAge epigenetic age deviation ( B = -0.10 years, 95% CI: -0.19, -0.02). No associations were observed for menarche timing. This suggests a connection between earlier menopause and biological aging, with potential clinical implications for identifying those at high risk for age-related disease.

Exposure to pollutants and chemicals during critical developmental periods in early life can impact health and disease risk across the life course. Research in environmental epigenetics has provided increasing evidence that prenatal exposures affect epigenetic markers, particularly DNA methylation. In this article, we discuss the role of DNA methylation in early life programming and review evidence linking the intrauterine environment to epigenetic modifications, with a focus on exposure to tobacco smoke, metals, and endocrine-disrupting chemicals. We also discuss challenges and novel approaches in environmental epigenetic research and explore the potential of epigenetic biomarkers in studies of pediatric populations as indicators of exposure and disease risk. Overall, we aim to highlight how advancements in environmental epigenetics may transform our understanding of early-life exposures and inform new approaches for supporting long-term health.

Blood-based, observational, and cross-sectional epidemiological studies suggest that air pollutant exposures alter biological aging. In a single-blinded randomized crossover human experiment of seventeen volunteers, we examined the effect of randomized 2-hour controlled air pollution exposures on respiratory tissue epigenetic aging. Bronchial epithelial cell DNA methylation (DNAm) 24-hours post-exposure was measured using the HumanMethylation450K BeadChip, and there was a minimum 2-week washout period between exposures. All seventeen volunteers were exposed to ozone, but only thirteen were exposed to diesel exhaust. Horvath DNAmAge (Pearson coefficient [r]=0.64; Median Absolute Error [MAE]=2.7-years), GrimAge (r=0.81; MAE=13-years), and DNAm Telomere Length (DNAmTL) (r=-0.65) were strongly correlated with chronological age in this tissue. Compared to clean air, ozone exposure was associated with longer DNAmTL (median difference 0.11kb, Fisher-exact p-value=0.036). This randomized trial suggests a weak relationship of ozone exposure with DNAmTL in target respiratory cells. Still, causal relationships with long-term exposures need to be evaluated.