Measuring the impact of socioeconomic status on biological aging, now in real-time
A second study, by Laurel Raffington, PhD, of the University of Texas at Austin, and colleagues, evaluated the relationship between socioeconomic disadvantage in childhood and pace of biological aging.
To do so, they used the DunedinPoAm DNA methylation algorithm, a relatively new tool that was developed by analyzing changes in organ system integrity over time among adults with the same chronological age.
“Whereas epigenetic clocks quantify the amount of aging that has already occurred up to the time of measurement, DunedinPoAm quantifies how fast an individual is aging,” Dr. Raffington and colleagues wrote. “In other words, whereas epigenetic clocks tell you what time it is, pace-of-aging measures tell you how fast the clock is ticking.”
The investigators measured pace of aging in 600 children and adolescents (8-18 years of age) from the Texas Twin Project, “an ongoing longitudinal study that includes the collection of salivary samples.” The final dataset included 457 participants who identified as White, 77 who identified as Latinx, and 61 who identified as both White and Latinx.
The investigators evaluated pace of aging compared with family-level and neighborhood-level socioeconomic status, and tested for confounding by tobacco exposure, BMI, and pubertal development.
This analysis revealed that children experiencing socioeconomic disadvantage were aging more quickly than their peers, in terms of both family-level and neighborhood-level inequity (both levels, r = 0.18; P = .001).
Children who identified as Latinx aged faster than did those who identified as White only or White and Latinx, “consistent with higher levels of disadvantage in this group,” the investigators wrote. “Thus, our findings are consistent with observations that racial and/or ethnic socioeconomic disparities are an important contributor to racial and/or ethnic disparities in health.”
Higher BMI, greater tobacco exposure, and more advanced pubertal development were also associated with more rapid aging. After adjustment for these covariates, however, the significant correlation between socioeconomic disadvantage and rapid aging remained, the investigators noted.
“Our results suggest that salivary DNA methylation measures of pace of aging may provide a surrogate or intermediate endpoint for understanding the health impacts of [childhood] interventions,” the investigators concluded. “Such applications may prove particularly useful for evaluating the effectiveness of health-promoting interventions in at-risk groups.”
Still, more work is needed to understand exactly how socioeconomic disadvantage is associated with accelerated aging.
“Ultimately, not only longitudinal repeated-measures studies but also natural experiment studies and randomized controlled trials of social programs are needed to establish causal effects of social disadvantage on DunedinPoAm-measured pace of aging and to establish DunedinPoAm as a mediator of the process through which childhood disadvantage leads to aging-related health conditions,” the investigators wrote.
In his editorial, Dr. Notterman emphasized this point.
“[I]t is worth remembering that associations with either methylation age or pace of aging and health or longevity may represent the effect of an exposure on both the measure and the outcome of interest rather than a causal pathway that runs from the exposure (low socioeconomic status, adversity) to health outcome (i.e., cancer, vascular disease),” he wrote.
Paul Chung, MD, professor and chair of health systems science at Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, Calif., and adjunct professor at the University of California, Los Angeles, called the findings “preliminary,” but noted that confirmation through further research could “fill in some really important gaps.
“Right now, to some degree, we’re at a little bit of an impasse,” Dr. Chung said.
Adverse childhood experiences are “associated very strongly” with mental and physical health issues, Dr. Chung said, “but we don’t know exactly why, and because of that, it’s really hard to come up with social policy solutions that aren’t anything but extremely sort of blunt-ended. We just say, ‘Well, I guess you gotta fix everything.’ And it’s a hard place to be, I think, in the field.”
Although the present study doesn’t resolve this issue, Dr. Chung suggested that the findings “really open the door to a lot of really exciting research that could have a lot of impacts on practice and policy.”
“Sometimes the only way to get people to pay attention enough to generate the level of excitement that would allow you to even do these sorts of studies ... is to generate some initial exploratory data that makes people perk up their ears, and makes people go, ‘Hey, wow, maybe we should be looking into this.’ ”
The study by Dr. Raffington and colleagues was funded by the National Institutes of Health and the Jacobs Foundation, with additional support from the German Research Foundation, Russell Sage Foundation Biology and Social Science Grant, the Canadian Institute for Advanced Research Child and Brain Development Network, and others. The study by Dr. Lieshout and colleagues was supported by Canadian Institutes of Health Research. Dr. Factor-Litvak and Dr. Notterman reported funding from the National Institutes of Health. All of the investigators and interviewees reported no conflicts of interest.