Among older Americans, many age-related health outcomes disparities are extensive and persistent. It reflects weathering, the biologically accelerated aging of Black Americans compared to White Americans. The factors in the environment that affect weathering are poorly understood. A strong correlation exists between higher biological age—determined by DNA methylation (DNAm)—than chronological age and worse age-related outcomes and increased social adversity.
A new study published in PLoS One suggests that individual socioeconomic status (SES), neighborhood social environment, and air pollution exposures contribute to racial disparities in DNAm aging according to GrimAge and Dunedin Pace of Aging methylation (DPoAm).
According to social epigenetics, DNA methylation (DNAm) mediates the relationship between social and structural health determinants, age-related health outcomes, and health disparities. The circumstances in which people are born, live, learn, work, and age are social and structural health determinants. Although it is well established that these factors play a significant role in aging-related health and health disparities, little is understood about the biological processes through which they influence health outcomes. There is evidence to suggest that one of these mechanisms is DNA aging.
The neighborhood’s social and physical environments are important determinants of age-related health. Neighborhood socioeconomic deprivation, perceived neighborhood disorder, and air pollution exposure have all been linked to health status and decline in older adults. A growing body of research shows that living in a neighborhood with a more significant proportion of people with low socioeconomic resources is associated with many adverse health outcomes for older adults regardless of their individual.
There are mixed results on the health effects of perceived social and physical disorder in one’s neighborhood. Still, the disorder is associated with a risk of functional decline, cardiovascular disease, and dementia. Exposure to fine particulate matter (PM2.5) air pollution is an established risk factor for mortality and several age-related diseases, and nitrogen dioxide (NO2) is associated with several of these outcomes.
In this study, scientists examined the extent to which racial differences in DNA aging are caused by differing levels of neighborhood exposure and associated risks among older Black and White Americans.
Scientists conducted retrospective cross-sectional analyses on 2,960 non-Hispanic participants from the Health and Retirement Study (82% White, 18% Black), whose 2016 DNAm age is connected to survey responses and geographic information.
866,091 CpG sites had their DNAm evaluated using the Infinium Methylation EPIC BeadChip. Samples were run in duplicate, randomized among plates, and quality-controlled. Based on published CpG sites and weights, values for the GrimAge and Dunedin Pace of Aging methylation (DPoAm) were estimated.
They used census-tract-level data based on participants’ census tract of residence in 2014, the most recent year before the outcome measurement, for exposure to neighborhood socioeconomic deprivation and air pollution.
Scientists measured reported local social and physical disorders using participant assessments of their neighborhood from the Psychosocial and Lifestyle Questionnaire. Respondents indicated how much they agreed with each of the eight assertions on a seven-point scale. Four comments in their area are about social dysfunction, and four are about physical disorders. Higher scores indicate a greater perceived disorder.
Excluded from the study were those who identified as Hispanic, Latino, or a race other than Black or White. The HRS poll does not differentiate between assigned sex and gender identification and sees gender as a binary. Since “sex-mismatched” blood samples were excluded from DNAm measurement, this dataset likely lacks trans or intersex persons. The number of years of formal schooling completed determines the category of education.
To prevent collinearity, scientists employed an indicator of household wealth and income.
The results showed that Black individuals have significantly accelerated DNAm aging on average compared to White individuals, according to GrimAge (239%) and DPoAm (238%).
When implementing multivariable linear regression models and threefold decomposition to identify exposures contributing to this disparity, scientists found that individual-level SES is strongly associated with and accounts for a large portion of the disparity in GrimAge and DPoAm aging.
Scientists noted, “Higher neighborhood deprivation for Black participants significantly contributes to the disparity in GrimAge aging. Black participants are more vulnerable to fine particulate matter exposure for DPoAm, perhaps due to individual- and neighborhood-level SES, which may contribute to the disparity in DPoAm aging. DNAm aging may play a role in the environment “getting under the skin,” contributing to age-related health disparities between older Black and White Americans.”