Normative Aging Study Participants Research Articles

Solar and Geomagnetic Activity Reduces Pulmonary Function and Enhances Particulate Pollution Effects

Background: Increased solar and geomagnetic activity (SGA) may alter sympathetic nervous system activity, reduce antioxidant activity, and modulate physiochemical processes that contribute to atmospheric aerosols, all which may reduce pulmonary function. Aim: Investigate associations between forced expiratory volume at 1 second (FEV1) and forced vital capacity (FVC) with SGA, and assess whether SGA enhances adverse effects of black carbon (BC) and particulate matter ≤2.5 μm in diameter (PM2.5). Methods: We conducted a repeated measures analysis in 726 Normative Aging Study participants (Boston, USA) between 2000 and 2017, using interplanetary magnetic field (IMF), planetary K index (Kp), and sunspot number (SSN) as SGA measures. Linear mixed effects models were used to assess exposure moving averages up to 28 days for both SGA and pollution. Results: Increases in IMF, Kp Index and SSN from the day of the pulmonary function test averaged through day 28 of were associated with a significant decrement in FEV1 and FVC, after adjusting for potential confounders. There were greater effects for longer moving averages and enhanced effects of PM2·5 and BC on FEV1 and FVC with increased SGA. For example, for each inter-quartile increase (4.55 µg/m3) in average PM2·5 28 days before testing, low IMF (10th percentile: 3.2 nT) was associated with a -21.4 ml (95% CI:-60.8, 18.1) and -7.1 ml (95% CI:-37.7, 23·4) decrease in FVC and FEV1, respectively; high IMF (90th percentile: 9.0 nT) was associated with a -120.7 ml (95% CI:-166.5, -74.9) and -78.6 ml (95% CI: -114.3, -42·8) decrease in FVC and FEV1, respectively. Conclusion: Increased periods of SGA may directly contribute to impaired lung function and enhance effects of PM2.5 and BC. Since exposure to solar activity is ubiquitous, stricter measures in reducing air pollution exposures are warranted, particularly in elderly populations. Keywords: Pulmonary Function , Air pollution, Solar and Geomagnetic Activity

Extracellular microRNA and cognitive function in a prospective cohort of older men: The Veterans Affairs Normative Aging Study.

Background: Aging-related cognitive decline is an early symptom of Alzheimer’s disease and other dementias, and on its own can have substantial consequences on an individual’s ability to perform important everyday functions. Despite increasing interest in the potential roles of extracellular microRNAs (miRNAs) in central nervous system (CNS) pathologies, there has been little research on extracellular miRNAs in early stages of cognitive decline. We leverage the longitudinal Normative Aging Study (NAS) cohort to investigate associations between plasma miRNAs and cognitive function among cognitively normal men.Methods: This study includes data from up to 530 NAS participants (median age: 71.0 years) collected from 1996 to 2013, with a total of 1,331 person-visits (equal to 2,471 years of follow up). Global cognitive function was assessed using the Mini-Mental State Examination (MMSE). Plasma miRNAs were profiled using small RNA sequencing. Associations of expression of 381 miRNAs with current cognitive function and rate of change in cognitive function were assessed using linear regression (N = 457) and linear mixed models (N = 530), respectively.Results: In adjusted models, levels of 2 plasma miRNAs were associated with higher MMSE scores (p < 0.05). Expression of 33 plasma miRNAs was associated with rate of change in MMSE scores over time (p < 0.05). Enriched KEGG pathways for miRNAs associated with concurrent MMSE and MMSE trajectory included Hippo signaling and extracellular matrix-receptor interactions. Gene targets of miRNAs associated with MMSE trajectory were additionally associated with prion diseases and fatty acid biosynthesis.Conclusions: Circulating miRNAs were associated with both cross-sectional cognitive function and rate of change in cognitive function among cognitively normal men. Further research is needed to elucidate the potential functions of these miRNAs in the CNS and investigate relationships with other neurological outcomes.

Extracellular Vesicle-Encapsulated microRNAs as Novel Biomarkers of Lung Health.

Rationale: Early detection of respiratory diseases is critical to facilitate delivery of disease-modifying interventions. Extracellular vesicle-enriched microRNAs (EV-miRNAs) may represent reliable markers of early lung injury. Objectives: Evaluate associations of plasma EV-miRNAs with lung function. Methods: The prospective NAS (Normative Aging Study) collected plasma EV-miRNA measurements from 1996-2015 and spirometry every 3-5 years through 2019. Associations of EV-miRNAs with baseline lung function were modeled using linear regression. To complement the individual miRNA approach, unsupervised machine learning was used to identify clusters of participants with distinct EV-miRNA profiles. Associations of EV-miRNA profiles with multivariate latent longitudinal lung function trajectories were modeled using log binomial regression. Biological functions of significant EV-miRNAs were explored using pathway analyses. Results were replicated in an independent sample of NAS participants and in the HEALS (Health Effects of Arsenic Longitudinal Study). Measurements and Main Results: In the main cohort of 656 participants, 51 plasma EV-miRNAs were associated with baseline lung function (false discovery rate-adjusted P value < 0.05), 28 of which were replicated in the independent NAS sample and/or in the HEALS cohort. A subset of participants with distinct EV-miRNA expression patterns had increased risk of declining lung function over time, which was replicated in the independent NAS sample. Significant EV-miRNAs were shown in pathway analyses to target biological pathways that regulate respiratory cellular immunity, the lung inflammatory response, and airway structural integrity. Conclusions: Plasma EV-miRNAs may represent a robust biomarker of subclinical lung injury and may facilitate early identification and treatment of patients at risk of developing overt lung disease.

Solar and geomagnetic activity reduces pulmonary function and enhances particulate pollution effects

BackgroundIncreased solar and geomagnetic activity (SGA) may alter sympathetic nervous system activity, reduce antioxidant activity, and modulate physiochemical processes that contribute to atmospheric aerosols, all which may reduce pulmonary function. ObjectivesInvestigate associations between forced expiratory volume at 1 s (FEV1) and forced vital capacity (FVC) with SGA, and assess whether SGA enhances adverse effects of particulate pollution, black carbon (BC) and particulate matter ≤2.5 μm in diameter (PM2.5). Methods: We conducted a repeated measures analysis in 726 Normative Aging Study participants (Boston, Massachusetts, USA) between 2000 and 2017, using interplanetary magnetic field (IMF), planetary K index (Kp), and sunspot number (SSN) as SGA measures. Linear mixed effects models were used to assess exposure moving averages up to 28 days for both SGA and pollution. ResultsIncreases in IMF, Kp Index and SSN from the day of the pulmonary function test averaged through day 28 of were associated with a significant decrement in FEV1 and FVC, after adjusting for potential confounders. There were greater effects for longer moving averages and enhanced effects of PM2.5 and BC on FEV1 and FVC with increased SGA. For example, for each inter-quartile increase (4.55 μg/m3) in average PM2.5 28 days before testing, low IMF (10th percentile: 3.2 nT) was associated with a −21.4 ml (95 % CI: −60.8, 18.1) and −7.1 ml (95 % CI: −37.7, 23·4) decrease in FVC and FEV1, respectively; high IMF (90th percentile: 9.0 nT) was associated with a −120.7 ml (95 % CI:-166.5, −74.9) and −78.6 ml (95 % CI: −114.3, −42·8) decrease in FVC and FEV1, respectively. DiscussionIncreased periods of solar and geomagnetic activity may directly contribute to impaired pulmonary function and also enhance effects of PM2.5 and BC. Since exposure to solar activity is ubiquitous, stricter measures in reducing air pollution exposures are warranted, particularly in elderly populations.

Embracing a “Compound” Exposome Approach to Better Understand Environment and DNA Methylation Age Relationships

BACKGROUND AND AIM: DNA methylation-based measures of aging remain a promising focus of research because they offer the possibility of detecting adverse changes in human physiology before the onset of clinical disease. This is particularly important in the context of environmental pollutants, because exposure to toxicants can often be intervened upon. METHODS: In a series of studies using data from male VA Normative Aging Study (NAS) and Mars-500 mission participants, we evaluated relationships of long-term environmental exposures with blood leukocyte measures of DNA methylation age. RESULTS:In NAS participants, an IQR increase in one-year PM2.5 (β = 0.64-years, 95%CI: 0.20, 1.09, P = 0.005), sulfate (β = 0.51-years, 95%CI: 0.28, 0.74, P 0.0001), and ammonium (β = 0.36-years, 95%CI: 0.02, 0.70, P = 0.04) were associated with increases in DNA methylation age. These relationships were significantly modified by endothelial function variant scores, mitochondrial haplogroups, and miRNA-processing alleles. In Mars-500 participants, mission duration was associated with decreases in DNA methylation aging (β = -5.41-years, 95%CI: −8.70, −2.12, P = 0.003). CONCLUSIONS:Still, it remains unclear if these relationships apply to all persons. Adopting an exposome approach that facilitates more comprehensive exposure-disease pathway characterizations across domains including the social exposome and neighborhood factors remains an important step to better understanding these and other DNA methylation age relationships with environmental factors. Exposome-centered study designs should also be supported with efforts to increase the recruitment and retention of racially diverse study populations and researchers, and further “compounded” with efforts to improve the use and interpretation of race throughout the publication and dissemination process. Such a “compound” exposome approach expands the ability of research to identify DNA methylation-based aging biomarkers that explicate racial disparities in health. A compound exposome approach also better positions the environmental research community to contribute to the elimination of racial health disparities. KEYWORDS: Epigenetic Aging, Exposome, Equity, DNA Methylation Age

Associations of Plasma Folate and Vitamin B6 With Blood DNA Methylation Age: An Analysis of One-Carbon Metabolites in the VA Normative Aging Study.

One-carbon metabolism is an important contributor to aging-related diseases; nevertheless, relationships of one-carbon metabolites with novel DNA methylation-based measures of biological aging remain poorly characterized. We examined relationships of one-carbon metabolites with 3 DNA methylation-based measures of biological aging: DNAmAge, GrimAge, and PhenoAge. We measured plasma levels of 4 common one-carbon metabolites (vitamin B6, vitamin B12, folate, and homocysteine) in 715 VA Normative Aging Study participants with at least 1 visit between 1999 and 2008 (observations = 1153). DNA methylation age metrics were calculated using the HumanMethylation450 BeadChip. We utilized Bayesian Kernel Machine Regression models adjusted for chronological age, lifestyle factors, age-related diseases, and study visits to determine metabolites important to the aging outcomes. Bayesian Kernel Machine Regression models allowed for the estimation of the relationships of single metabolites and the cumulative metabolite mixture with methylation age. Log vitamin B6 was selected as important to PhenoAge (β = -1.62 years, 95% CI: -2.28, -0.96). Log folate was selected as important to GrimAge (β = 0.75 years, 95% CI: 0.41, 1.09) and PhenoAge (β = 1.62 years, 95% CI: 0.95, 2.29). Compared to a model where each metabolite in the mixture is set to its 50th percentile, the log cumulative mixture with each metabolite at its 30th (β = -0.13 years, 95% CI: -0.26, -0.005) and 40th percentile (β = -0.06 years, 95% CI: -0.11, -0.005) was associated with decreased GrimAge. Our results provide novel characterizations of the relationships between one-carbon metabolites and DNA methylation age in a human population study. Further research is required to confirm these findings and establish their generalizability.

Correlation over time of toenail metals among participants in the VA normative aging study from 1992 to 2014.

BackgroundScientists use biomarkers to evaluate metal exposures. One biomarker, toenails, is easily obtained and minimally invasive, but less commonly used as a biomarker of exposure. Their utility will depend on understanding characteristics of their variation in a population over time. The objective of our study is to describe the correlation of toenail metal levels many years apart among participants in the VA Normative Aging Study (NAS).MethodsToenail clippings from 825 participants of the NAS from year 1992 to 2014 were analyzed for lead (Pb), Arsenic (As), Cadmium (Cd), Manganese (Mn), and Mercury (Hg). We utilized linear mixed models to assess correlation between toenail metal concentrations in multiple toenail samples from the same subject collected years apart and identified the optimal covariance pattern by likelihood ratio tests and Akaike’s information criterion (AIC). Correlations among different metals were described using Spearman correlations.ResultsThe average number of times toenail samples were collected from each subject ranged from 1.63 (Hg) to 2.04 (As). The average number of years between toenails collected per subject ranged from 4.73 (SD=2.44) (Mn) to 5.35 (SD=2.69) (Hg). Metal concentrations had slightly different correlation patterns over time, although for all metals correlations decreased with increasing time between samples. Estimated correlations over a 3-year span were highest for toenail Pb (0.68) and Hg (0.67), while As, Cd, and Mn had lower correlations of 0.49, 0.44, and 0.47, respectively. Even across a six-year span, the lowest correlation was 0.35 (Cd).ConclusionOur results suggest that Pb, As, Cd, Mn, and Hg levels from toenail clippings can reasonably reflect exposures over several years in elderly men in the NAS. Even across six years, toenail metal levels were generally well correlated among NAS participants. As such, they may be useful as biomarkers of exposure in epidemiological studies of similar populations.

Correlation over Time of Toenail Metals among Participants in the VA Normative Aging Study from 1992 to 2014

Scientists use biomarkers to evaluate metal exposures. One biomarker, toenails, is easily obtained and minimally invasive, but less commonly used as a biomarker of exposure. Their utility will depend on understanding characteristics of their variation in a population over time. The objective of our study is to describe the correlation of toenail metal levels many years apart among participants in the VA Normative Aging Study (NAS). Toenail clippings from 825 participants of the NAS from year 1992 to 2014 were analyzed for lead (Pb), Arsenic (As), Cadmium (Cd), Manganese (Mn), and Mercury (Hg). We utilized linear mixed models to assess correlation between toenail metal concentrations in multiple toenail samples from the same subject collected years apart and identified the optimal covariance pattern by likelihood ratio tests and Akaike’s information criterion (AIC). Correlations among different metals were described using Spearman correlations. The average number of times toenail samples were collected from each subject ranged from 1.63 (Hg) to 2.04 (As). The average number of years between toenails collected per subject ranged from 4.73 (SD = 2.44) (Mn) to 5.35 (SD = 2.69) (Hg). Metal concentrations had slightly different correlation patterns over time, although for all metals correlations decreased with increasing time between samples. Estimated correlations over a 3-year span were highest for toenail Pb (0.68) and Hg (0.67), while As, Cd, and Mn had lower correlations of 0.49, 0.44, and 0.47, respectively. Even across a 6-year span, the lowest correlation was 0.35 (Cd). Our results suggest that Pb, As, Cd, Mn, and Hg levels from toenail clippings can reasonably reflect exposures over several years in elderly men in the NAS. Even across 6 years, toenail metal levels were generally well correlated among NAS participants. As such, they may be useful as biomarkers of exposure in epidemiological studies of similar populations.

Impacts of the Mitochondrial Genome on the Relationship of Long-Term Ambient Fine Particle Exposure with Blood DNA Methylation Age.

The mitochondrial genome has long been implicated in age-related disease, but no studies have examined its role in the relationship of long-term fine particle (PM2.5) exposure and DNA methylation age (DNAm-age)-a novel measure of biological age. In this analysis based on 940 observations between 2000 and 2011 from 552 Normative Aging Study participants, we determined the roles of mitochondrial DNA haplogroup variation and mitochondrial genome abundance in the relationship of PM2.5 with DNAm-age. We used the GEOS-chem transport model to estimate address-specific, one-year PM2.5 levels for each participant. DNAm-age and mitochondrial DNA markers were measured from participant blood samples. Nine haplogroups (H, I, J, K, T, U, V, W, and X) were present in the population. In fully adjusted linear mixed-effects models, the association of PM2.5 with DNAm-age (in years) was significantly diminished in carriers of haplogroup V (Pinteraction = 0.01; β = 0.18, 95%CI: -0.41, 0.78) compared to noncarriers (β = 1.25, 95%CI: 0.58, 1.93). Mediation analysis estimated that decreases in mitochondrial DNA copy number, a measure of mitochondrial genome abundance, mediated 12% of the association of PM2.5 with DNAm-age. Our data suggests that the mitochondrial genome plays a role in DNAm-age relationships particularly in the context of long-term PM2.5 exposure.

Abstract 4251: DNA methylation of mitochondrial biogenesis regulating genes: A possible link between telomeres, mitochondria, and cancer incidence

Abstract Background: PGC1A and PGC1B encode transcriptional factors that regulate mitochondrial biogenesis and have been implicated as a link between telomeric and mitochondrial functions. Telomere dysfunction is associated with impaired mitochondrial biogenesis and increased generation of reactive oxygen species. Animal studies have also shown that loss of PGC1A protects against cancer as mitochondrial function is required for transformation and tumor growth. No human studies have examined the role of these genes in relation to cancer incidence. Our objective was to examine associations between PGC1A and PGC1B methylation in relation to cancer incidence. Methods: We studied 491 Normative Aging Study participants who had blood drawn 1-4 times from 1999 through 2012. After median 10.2-year follow-up, there were 125 incident cancers including 36 prostate. PGC1A and PGC1B methylation was measured at 30 and 27 sites, respectively, using the HumanMethylation450k assay. We used Cox proportional hazards models to examine associations between CpG methylation and cancer incidence measured at first blood draw as well as in time-dependent associations. All models adjusted for age, race, smoking status and pack-years, alcohol consumption, blood cell composition, and processing batch. Results: In single-site adjusted time-dependent models, we identified 13 instances of 11 individual loci (10 from PGC1A and 1 from PGC1B) significantly associated with all-cancer and prostate cancer incidence. In multi-site adjusted models, we showed cg0677257 from the 3’ UTR of PGC1A was inversely associated with first-visit (HR: 0.41; 95% CI: 0.21, 0.79) and time-dependent all-cancer incidence (HR: 0.42; 95% CI: 0.22, 0.81). Similarly, we showed cg0942771 and cg03281309 from the gene body of PGC1A were inversely associated with time-dependent all-cancer incidence (HR: 0.51; 95% CI: 0.30, 0.88; HR: 0.74; 95% CI: 0.56, 0.98, respectively). Finally, we found that cg1521939 from the 5’ UTR region of PGC1B was positively associated with time-dependent all-cancer incidence (HR: 3.27; 95% CI: 1.55, 6.90). Conclusion: This is the first study in humans to show site-specific PGC1A and PGC1B methylation is a significant predictor of cancer incidence. These findings point to a possible interplay between telomere and mitochondrial dysfunction, and epigenetics in carcinogenesis. Additional studies should also examine these associations in larger cohorts with greater racial/ethnic, gender, and socioeconomic diversity to validate these findings. Citation Format: Jacob K. Kresovich, Tao Gao, Brian T. Joyce, Pantel Vokonas, Joel Schwartz, Andrea A. Baccarelli, Lifang Hou. DNA methylation of mitochondrial biogenesis regulating genes: A possible link between telomeres, mitochondria, and cancer incidence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4251. doi:10.1158/1538-7445.AM2017-4251

Abstract LB-368: Mitochondrial DNA and cancer in the normative aging study

Abstract Background: Mitochondrial DNA (mtDNA) is a potentially sensitive marker of damage by reactive oxygen species (ROS). Two biomarkers in mtDNA, copy number (mtDNAcn) and 8-OHdG, have therefore been proposed as potential markers of oxidative stress and therefore carcinogenesis. Prospective human studies subjects of mtDNAcn have found inconsistent results, but many suggest that the interval between mtDNAcn measurement and cancer diagnosis affects the association. Moreover, prior studies suggest that the interplay of mtDNAcn and 8-OHdG reflect ongoing oxidative stress related to carcinogenesis, suggesting their potential use in tandem as an early detection biomarker of cancer. Our objective was to examine longitudinal associations between mtDNAcn and 8-OHdG measured in whole blood in relation to both cancer incidence and mortality. Methods: We studied 526 Normative Aging Study participants who had blood drawn 1-4 times from 1999 through 2012 and who were cancer free at first blood draw (median 9.7 years between blood draw and cancer diagnosis/censoring). mtDNAcn and 8-OHdG were measured using quantitative real-time PCR. We used Cox proportional hazards regression models to examine associations between mtDNAcn and mitochondrial 8-OHdG measured at the first blood draw only as well as time-dependent associations across a total of 1043 blood draws and time to all-cancer diagnosis. We ran a second set of models stratified by time between blood draw and diagnosis/censoring, and a third set that explored possible interaction between mtDNAcn and 8-OHdG via inclusion of a product term. All models adjusted for age, BMI, white blood cell count, proportion neutrophils, race, education, smoking status, pack-years of smoking, and alcohol consumption. Results: We found no significant associations between pre-diagnostic mtDNAcn and time to cancer diagnosis or death. When measured at the first blood draw only, 8-OHdG was inversely associated with all-cancer (HR: 0.17; 95% CI: 0.03-0.87) and prostate cancer incidence (HR: 0.05; 95% CI: 0.00-0.97). In the time-dependent models, mitochondrial 8-OHdG was inversely associated with time to all-cancer diagnosis (HR: 0.31; 95% CI: 0.10-1.01) and positively associated with time to all-cancer death (HR: 1.83; 95% CI: 1.13-2.98), while mtDNAcn was positively and independently associated with time to all-cancer death (HR: 1.59; 95% CI: 1.17-2.15; pinteraction = 0.96). In the stratum of 4-6 years between blood draw and diagnosis, 8-OHdG was associated with cancer incidence (HR: 0.01; 95% CI: 0-1.00). Modeling 8-OHdG and mtDNAcn together produced no noteworthy changes in results. Similarly, the test for interaction was non-significant across all models. Conclusion: Pre-diagnostic mtDNAcn does not appear to be significantly associated with cancer, however mitochondrial 8-OHdG may be a significant predictor of cancer several years prior to diagnosis. Mitochondiral markers of oxidative stress may also be significant predictors of cancer mortality, possibly related to metastasis and/or treatment. Additional prospective studies in larger cohorts with greater racial/ethnic, gender, and socioeconomic diversity are needed to validate the utility of 8-OHdG as an early detection biomarker of cancer. Future studies of mitochondrial oxidative stress markers measurable in blood and cancer mortality are warranted. Citation Format: Brian T. Joyce, Tao Gao, Yinan Zheng, Lei Liu, Andrea Baccarelli, Joel Schwartz, Lifang Hou. Mitochondrial DNA and cancer in the normative aging study. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-368.

Abstract A17: Physical activity and epigenetic age among normative aging study participants

Abstract Low levels of physical activity are associated with increased risk and mortality of common cancers including breast and colon, with strong evidence for increasing risk with age. Epigenetic age is a recently developed concept using DNA methylation measurements to describe biological age at the level of human tissues, cells, and organs. Epigenetic age represents deviation from expected DNA methylation patterns associated with chronological age (defined as Δ_age), and is suggested as a possible biological mechanism driving observed associations between physical activity and cancer risk. However, no studies have evaluated associations between physical activity level and Δ_age. The Normative Aging Study (NAS) is a cohort study of healthy aging conducted by the Veterans Affair Administration. Among NAS participants (n=656), we conducted multivariate linear regression to prospectively evaluate associations between physical activity (MET-hours per week) and Δ_age across two follow-up visits. The visits were on average 3.6 years apart, with a range of 2-8 years. Δ_age was estimated using Horvath’s DNA methylation online calculator and based upon DNA methylation patterns at the 71 cytosine-phosphate-guanine (CpGs) loci used in Hannum’s model. The calculator accounts for cell proportion of white blood cells. We adjusted models for chronological age, body mass index, education, smoking, alcohol consumption, and prevalent cancer status. Overall, we observed statistically significant associations between high physical activity levels and lower Δ_age, or younger epigenetic age. Among individuals reporting the highest level of physical activity (≥ 30 MET-hours per week), Δ_age was 1.44 (95% CI: 0.43 to 2.45) and 2.20 (95% CI: 1.04 to 3.36) years lower compared to those reporting low activity (&amp;lt;12 MET-hours per week) at the first and second visit, respectively. Furthermore, compared to low physical activity, high activity at the first visit was associated with 2.46 (95% CI: 1.25 to 3.67) years lower Δ_age at the second visit, and 3.72 (95% CI: 1.08 to 6.36) months/calendar year lower Δ_age rate of change, or decelerated epigenetic aging over time. In summary, the results of the current study demonstrate that physical activity influences DNA methylation patterns at the CpG loci associated with epigenetic age. Future studies are necessary to characterize further the relationship between physical activity and epigenetic age, especially as a potential biological mechanism of action in carcinogenesis. However, epigenetic age represents a unique set of markers with the potential to identify high-risk populations and, in turn, develop interventions to mitigate risk of cancer. Citation Format: Elizabeth A. Hibler, Yinan Zheng, Lei Liu, Wei Zhang, Frank J. Penedo, Siobhan M. Phillips, David E. Conroy, Joel Schwartz, Pantel Vokonas, Andrea Baccarelli, Qi Dai, Lifang Hou. Physical activity and epigenetic age among normative aging study participants. [abstract]. In: Proceedings of the AACR Special Conference: Developmental Biology and Cancer; Nov 30-Dec 3, 2015; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(4_Suppl):Abstract nr A17.

Erratum: “Bias in Environmental Cohort Studies: The Example of Bone Lead and Mortality”

Unrecognized biases in prospective environmental cohort studies may result in under- or overestimating the health effects of the exposure under investigation. In this issue of EHP, researchers examine the problem of bias using data on lead exposure and mortality in men and directed acyclic graphs (DAGs) to illustrate causal relationships between variables that could bias results.1 The study data came from 835 white male participants, average age 67 years, who were part of the Normative Aging Study (NAS), which began in 1963. Between 1991 and 1999, the men had undergone measurement of lead in their patellas. For the current analysis, the researchers looked at associations between patella lead and mortality from all causes, from cardiovascular disease, and from ischemic heart disease. Bone lead, rather than blood lead, is a better biomarker for cumulative environmental exposure,2 and patella lead in particular has been associated in past studies with risk of ischemic heart disease death.3 Directed acyclic graphs helped researchers pinpoint areas where bias related to recruitment and participation may have affected the Normative Aging Study and similar studies. The authors used DAGs to visualize relationships among variables that applied to the NAS participants. DAGs link variables with directional arrows to identify those that may bias results. The present study focused on potential errors related to participant selection and participation issues that may affect other cohort studies used in environmental health research. By explicitly visualizing assumptions with DAGs, researchers can identify where bias creeps in and find ways to avoid it.4 “Researchers don’t always recognize the assumptions they make when analyzing data,” says study leader Marc Weisskopf, an epidemiologist at the Harvard T.H. Chan School of Public Health. As the team analyzed the DAGs, they realized that age at enrollment appeared to be influencing the risk associations. Overall, men with the highest patella lead levels were twice as likely as those with the lowest lead levels to die from ischemic heart disease. However, among the subset of 637 men who were 45 or younger when they entered the NAS cohort, those with the highest patella lead levels were estimated to be 4.6 times as likely to die from ischemic heart disease as those with the lowest levels. When the data were further adjusted to account for men who dropped out of the cohort, the estimated risk among younger men with the highest lead levels climbed to 5.2 times that of younger men with the lowest exposures.1 Men who were older when they enrolled in the NAS likely did not represent older men in general. That’s because many older men have cardiovascular conditions, which makes them less likely to participate in studies.5 Furthermore, the NAS specifically did not accept participants with pre-existing cardiovascular disease.1 In contrast, because younger people tend to be healthier, their health status is less likely to influence whether they enter a study. Ideally, long-term studies such as the NAS would follow younger participants for a longer time to avoid recruitment biases. However, the longer a cohort is followed, the more expensive the study becomes. “This is particularly problematic with environmental exposures that are related to health conditions that affect people’s likelihood of participating in studies,” Weisskopf says. “Younger people are healthier to start, and it’s less likely that a health condition drives who enters a study.” Socioeconomic status presents another source of potential bias. Less affluent people are both more likely to be exposed to environmental toxicants and less likely to participate in epidemiological studies, and those who do enroll are more likely to drop out.6 “It’s not random who drops out of a cohort,” notes Weisskopf. Aside from the bias-related findings, the results suggest that previous estimates of lead’s influence on mortality may have been overly conservative. “They hint that we may be underestimating the health effects of other environmental toxicant exposures as well, especially in the context of health outcomes in older people and/or exposures associated with selection and attrition,” says Jennifer Weuve, an associate professor of internal medicine at Chicago’s Rush Medical College, who was not involved in the analysis. She says the methods used by Weisskopf’s team could be applied to other environmental epidemiology cohorts to improve estimates of health risks.

Longitudinal Study of DNA Methylation of Inflammatory Genes and Cancer Risk.

Chronic inflammation plays a key role in cancer etiology. DNA methylation modification, one of the epigenetic mechanisms regulating gene expression, is considered a hallmark of cancer. Human and animal models have identified numerous links between DNA methylation and inflammatory biomarkers. Our objective was to prospectively and longitudinally examine associations between methylation of four inflammatory genes and cancer risk. We included 795 Normative Aging Study participants with blood drawn one to four times from 1999 to 2012 (median follow-up, 10.6 years). Promoter DNA methylation of IL6, ICAM-1, IFN, and TLR2 in blood leukocytes was measured using pyrosequencing at multiple CpG sites and averaged by gene for data analysis. We used Cox regression models to examine prospective associations of baseline and time-dependent methylation with cancer risk and compared mean methylation differences over time between cancer cases and cancer-free participants. Baseline IFN hypermethylation was associated with all-cancer (HR, 1.49; P = 0.04) and prostate cancer incidence (HR, 1.69; P = 0.02). Baseline ICAM-1 and IL6 hypermethylation were associated with prostate cancer incidence (HR, 1.43; P = 0.02; HR, 0.70; P = 0.03, respectively). In our time-dependent analyses, IFN hypermethylation was associated with all-cancer (HR, 1.79; P = 0.007) and prostate cancer (HR, 1.57; P = 0.03) incidence; and ICAM-1 and IL6 hypermethylation were associated with prostate cancer incidence (HR, 1.39; P = 0.02; HR, 0.69; P = 0.03, respectively). We detected significant ICAM-1 hypermethylation in cancer cases (P = 0.0003) 10 to 13 years prediagnosis. Hypermethylation of IFN and ICAM-1 may play important roles in early carcinogenesis, particularly that of prostate cancer. These methylation changes could inform the development of early detection biomarkers and potential treatments of inflammation-related carcinogenesis.

Cumulative lead exposure is associated with reduced olfactory recognition performance in elderly men: The Normative Aging Study

IntroductionOlfactory dysfunction has been identified as an early warning sign for Alzheimer's disease, Parkinson's disease, dementia and more. A few occupational and environmental exposures have also been associated with reduced olfactory function, although the effects of long term environmental exposure to lead on olfactory dysfunction have not been explored. Here we performed olfactory recognition testing in elderly men in a community-dwelling cohort and examined the association with cumulative lead exposure, as assessed by lead in tibial and patellar bone. MethodsOlfactory recognition was measured in 165 men from the Normative Aging Study (NAS) who had previously taken part in bone lead measurements using K-X-ray fluorescence (KXRF). Olfactory recognition was measured using the University of Pennsylvania Smell Identification Test (UPSIT). Associations between olfactory recognition, global cognition and cumulative lead exposure were estimated using linear regression, with additional adjustment for age, smoking, and functional polymorphism status for hemochromatosis (HFE), transferrin (TfC2), glutathione-s-transferase Pi1 (GSTP1) and apolipoprotein E (APOE) genotypes. Sensitivity analyses explored olfactory recognition in men with high global cognitive function as measured using the Mini-Mental Status Exam (MMSE). ResultsThe average age of the NAS participants at the time of olfactory recognition testing was 80.3 (standard deviation or SD=5.7) years. Mean tibia lead was 16.3 (SD=12.0)μg/g bone, mean patella lead was 22.4 (SD=14.4)μg/g bone, and mean UPSIT score was 26.9 out of 40 (SD=7.0). Consistent with previous findings, age at olfaction testing was negatively associated with UPSIT score. Tibia (but not patella) bone lead was negatively associated with olfaction recognition (per 15μg/g tibia lead: β=−1.57; 95% CI: −2.93, −0.22; p=0.02) in models adjusted for smoking and age. Additional adjustment for education did not significantly change results. Of all the genes explored, only the presence of one or more HFE variant alleles was significantly associated with olfaction recognition (HFE β=2.26; 95% CI: 0.09, 4.43; p=0.04). In a model containing the HFE term and a lead term, the tibia lead parameter estimate dropped by 21% (per 15μg/g tibia lead: β=−1.25; 95% CI: −2.64, 0.14; p=0.08) while the HFE term dropped 15% (β=1.91; 95% CI: −0.28, 4.10; p=0.09). None of the other gene terms were associated with olfactory recognition in this cohort, nor were any gene–lead interaction terms significant. Additional sensitivity analysis in men with MMSE scores of 25 or higher (n=149) showed a similar but slightly attenuated association between lead and olfactory recognition (per 15μg/g tibia lead β=−1.39; 95% CI: −3.00, 0.22; p=0.09). ConclusionCumulative exposure to lead is associated with reduced olfactory recognition in a cohort of elderly men. The association was similar but not significant in men with better cognitive function as measured by the MMSE. Iron metabolism gene status may also affect olfactory function.

Leukocyte Telomere Length and Cancer Risk: A Dynamic Problem

Leukocyte Telomere Length and Cancer Risk: A Dynamic Problem

Blood Telomere Length Attrition and Cancer Development in the Normative Aging Study Cohort

BackgroundAccelerated telomere shortening may cause cancer via chromosomal instability, making it a potentially useful biomarker. However, publications on blood telomere length (BTL) and cancer are inconsistent. We prospectively examined BTL measures over time and cancer incidence. MethodsWe included 792 Normative Aging Study participants with 1–4 BTL measurements from 1999 to 2012. We used linear mixed-effects models to examine BTL attrition by cancer status (relative to increasing age and decreasing years pre-diagnosis), Cox models for time-dependent associations, and logistic regression for cancer incidence stratified by years between BTL measurement and diagnosis. FindingsAge-related BTL attrition was faster in cancer cases pre-diagnosis than in cancer-free participants (pdifference=0.017); all participants had similar age-adjusted BTL 8–14years pre-diagnosis, followed by decelerated attrition in cancer cases resulting in longer BTL three (p=0.003) and four (p=0.012) years pre-diagnosis. Longer time-dependent BTL was associated with prostate cancer (HR=1.79, p=0.03), and longer BTL measured ≤4years pre-diagnosis with any (OR=3.27, p<0.001) and prostate cancers (OR=6.87, p<0.001). InterpretationAge-related BTL attrition was faster in cancer cases but their age-adjusted BTL attrition began decelerating as diagnosis approached. This may explain prior inconsistencies and help develop BTL as a cancer detection biomarker.

Modifying roles of glutathione S-transferase polymorphisms on the association between cumulative lead exposure and cognitive function

BackgroundGlutathione-S-transferase gene (GST) polymorphisms can result in variable ability of these enzymes to remove electrophilic substrates. We investigated whether the GSTP1 Val105 and GSTM1 deletion polymorphisms modify the lead-cognitive function association. MethodsWe used repeated measures analysis to compare the association between cumulative lead biomarkers—bone lead measured using K-shell X-Ray Fluorescence—and Mini-Mental State Exam (MMSE) score by GST variants, adjusted for covariates, among Normative Aging Study participants, a Boston-based prospective cohort of men. We had complete data for 698 men (providing 1292 observations) for GSTM1 analyses and 595 men (providing 1142 observations) for GSTP1 analyses. ResultsA 15μg/g higher tibia lead concentration (interquartile range of tibia lead) was associated with a 0.24 point decrement in MMSE score among GSTP1 Val105 variant carriers, which was significantly stronger than the association among men with only wild-type alleles (p=0.01). The association among GSTP1 Val105 carriers was comparable to that of 3 years of age in baseline MMSE scores. The association between tibia lead and MMSE score appeared progressively steeper in participants with increasingly more GSTP1 Val105 alleles. A modest association between tibia lead and lower MMSE score was seen among participants with the GSTM1 deletion polymorphism. Neither of the glutathione S-transferase variants was independently associated with cognitive function, nor with lead biomarker measures. The results pertaining to patella lead were similar to those observed for tibia lead. ConclusionOur results suggest that the GSTP1 Val105 polymorphism confers excess susceptibility to the cognitive effects of cumulative lead exposure.

Long-term Exposure to Black Carbon and Carotid Intima-Media Thickness: The Normative Aging Study

Background: Evidence suggests that air pollution is associated with atherosclerosis and that traffic-related particles are a particularly important contributor to the association.Objectives: We investigated the association between long-term exposure to black carbon, a correlate of traffic particles, and intima-media thickness of the common carotid artery (CIMT) in elderly men residing in the greater Boston, Massachusetts, area.Methods: We estimated 1-year average exposures to black carbon at the home addresses of Normative Aging Study participants before their first CIMT measurement. The association between estimated black carbon levels and CIMT was estimated using mixed effects models to account for repeated outcome measures. In secondary analyses, we examined whether living close to a major road or average daily traffic within 100 m of residence was associated with CIMT.Results: There were 380 participants (97% self-reported white race) with an initial visit between 2004 and 2008. Two or three follow-up CIMT measurements 1.5 years apart were available for 340 (89%) and 260 (68%) men, respectively. At first examination, the average ± SD age was 76 ± 6.4 years and the mean ± SD CIMT was 0.99 ± 0.18 mm. A one-interquartile range increase in 1-year average black carbon (0.26 µg/m3) was associated with a 1.1% higher CIMT (95% CI: 0.4, 1.7%) based on a fully adjusted model.Conclusions: Annual mean black carbon concentration based on spatially resolved exposure estimates was associated with CIMT in a population of elderly men. These findings support an association between long-term air pollution exposure and atherosclerosis.Citation: Wilker EH, Mittleman MA, Coull BA, Gryparis A, Bots ML, Schwartz J, Sparrow D. 2013. Long-term exposure to black carbon and carotid intima-media thickness: the Normative Aging Study. Environ Health Perspect 121:1061–1067; http://dx.doi.org/10.1289/ehp.1104845 [Online 2 July 2013]

Modifying Influence of the Delta-Aminolevulinic Acid Dehydratase Polymorphism on Lead in Bone, Erythrocytes, and Urine

ISEE-551 Objective: The delta-aminolevulinic acid dehydratase (ALAD) polymorphism has been shown in some studies to alter the impact of lead on kidney function and other health outcomes, which may be due to associated effects on lead binding and tissue distribution kinetics. We evaluated the modifying influence of the ALAD polymorphism on the interrelations between erythrocyte lead, urine lead, and bone lead, and ALAD interaction with bone and erythrocyte lead in association with plasma lead among older community-exposed men. Materials and Methods: Information on ALAD genotype, lead levels in blood, bone (measured using K-shell x-ray fluorescence), and urine were collected for 727 Normative Aging Study participants. We created a structural equation model (SEM) to simultaneously evaluate the association between erythrocyte lead (estimated from whole blood lead) and bone lead, and between urine lead with erythrocyte lead by ALAD genotype (1–2/2–2 vs. 1–1). A second SEM assessed the relation between a latent plasma lead covariate, using urine lead as a surrogate measure, and bone and erythrocyte lead among ALAD 1–2 and 1–1 carriers. Potential predictors of lead levels in urine, erythrocytes, and bone were included in the SEMs. Results: Of the 727 participants, 16% (113) were heterozygous (1–2) and 1% (7) were homozygous (2–2) for the ALAD-2 allele, respectively. Among both ALAD 1–2/2–2 and 1–1 carriers, patella bone lead was associated with higher erythrocyte lead (P<0.05). We observed significant associations between erythrocyte lead and higher urine lead (P<0.05), and between erythrocyte lead and higher plasma lead (P<0.05), respectively, which did not vary with respect to ALAD genotype. Conclusions: The results of this study do not provide evidence that the ALAD genotype modifies the association between erythrocyte lead and plasma lead. These findings should be confirmed in populations with different exposure profiles and account for potential temporal changes in the internal distribution of lead.