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DNA Methylation-Based 'Biological' Age Associated With Race, Poverty

NEW YORK – Household income below the poverty level and African American racial identity are associated with faster epigenetic aging, according to a new study.

"Environmental factors, including psychological stress, alter gene expression and physiological response through changes in the epigenome," the authors wrote. "DNA methylation may be the mediation mechanism for the negative consequences of environmental and psychosocial risk factors." 

Researchers at the National Institutes of Health's National Institute on Aging used a new DNA methylation biomarker called the Dunedin Pace of Aging Calculated from the Epigenome (DunedinPACE) score to capture the rate of aging in adult subjects. 

DunedinPACE scores are values scaled to a mean of 1, interpretable with reference to a rate of 1 year of biological aging per 1 year of chronological aging, according to the researchers. The DunedinPACE measure was trained on longitudinal clinical data over 20 years using 19 biomarkers among participants from the Dunedin Birth Cohort Study, a cohort of white individuals with chronological ages ranging from 26 to 45 years who were from Dunedin, New Zealand.

For their study, published in JAMA Network Open on Friday, the researchers used the data of 470 participants from the Healthy Aging in Neighborhoods of Diversity Across the Life Span (HANDLS), a population-based study of socioeconomically diverse African American and white adults aged 30 to 64 years at baseline in Baltimore, Maryland.

The researchers collected blood samples of these participants at two time points — Aug. 14, 2004, and June 22, 2009 — and profiled their DNA methylation levels using Illumina Human MethylationEPIC BeadChips.

The results revealed a mean DunedinPACE score for all study participants of 1.07, translating to 7 percent faster biological aging than chronological aging. However, individuals whose income was below the poverty level had higher DunedinPACE scores at the initial visit than individuals with income above poverty levels. Sex was not significantly associated with DunedinPACE scores in these analyses.

The findings also showed white Americans with higher household incomes had lower DunedinPACE scores suggesting that they could be biologically aging slower compared to all people with lower incomes. However, this wasn't the case with African Americans. Regardless of poverty status, African Americans had DunedinPACE scores higher than 1.

"DunedinPACE scores appeared to exhibit the consequences of adverse exposures for biological aging, particularly underscoring the added liability of race borne by African American participants," the authors wrote.

According to the authors, social determinants such as discrimination, education, class inequality, economic opportunity, and housing, in addition to poverty, could be associated with faster biological aging among African Americans. "Pinpointing the molecular factors that trigger this disjunction may help identify those at greatest risk of poor health outcomes," they wrote.

Highlighting the limitations of this study, the authors said that the sample size was relatively small, noting that a larger sample may provide greater power to detect the associations of other covariates, such as sex differences.

They also said that data collection from time points five years apart may be too short for the relatively young age group of the participants. "Collection of further data from additional time points will be important to test the associations over time and to confirm the curvilinearity of biological age," they wrote.