Nothing is permanent, not even your genes. More specifically, neither is the expression of genes as influenced by the environments that allow for development, or epigenetics. With this notion, researchers are interested in how experiences and social influences throughout development affect one’s health outcomes. Professor Thomas McDade, along with colleagues in Northwestern’s anthropology department and the Institute for Policy Research are interested in “how social environments, how economic environments shape our physiology and our health over the life course.”
"We’ve known for a long time that individuals and their families – the level of access to resources that they have – their wealth, their education, income, appearance – are really strong predictors of health and how long someone’s gonna live," McDade said. “They’re probably the most powerful predictors of health, but we don’t know how that happens.”
To begin to uncover these relationships, McDade and colleagues analyzed how patterns of DNA methylation interacts with patterns of socioeconomic status. This methylation is a biochemical marker laid down on top of genes that influences the likelihood of these genes being expressed; for example, DNA methylation plays a role in the development of an organism based on which genes are expressed and which are not, and whether this leads to positive outcomes or potentially negative ones such as tumors forming. An observational study was conducted through an ongoing cohort study, which follows a defined group of participants to draw associations between biological outcomes and factors affecting the lives of the participants.
In the case of this study, DNA methylation and socioeconomic status were compared, with results showing that lower socioeconomic status is associated with DNA methylation. To achieve this result, the study was conducted in the Philippines, in which pregnant women and their children had been studied since 1983. The researchers monitored their health and recorded their socioeconomic status. Due to recent advancements in genetic analysis, researchers at the University of British Columbia, who also collaborated in the study, were able to analyze DNA methylation at 450 thousand sites in the genome. These data allowed for McDade and colleagues to draw conclusions about how socioeconomic status affects genes.
Despite the current study showing that lower socioeconomic status correlates with greater DNA methylation, it only separated kids into two socioeconomic groups: high and low. Future studies will determine if methylation and socioeconomic status change along a gradient.
In addition, McDade would like to study how methylation occurs as a proxy for life experiences via socioeconomic status in other locations and cultures. However, there are challenges to this since not many longitudinal cohort studies, such as the one in the Philippines, are available in other countries. With that in mind, McDade predicts that the fewer methylation sites will be associated with socioeconomic status in countries like the United States than the Philippines. He hypothesizes that the discrepancy will be due to the differences in what constitutes poverty in the different countries and what this would entail for lifestyle.
These findings have fascinating implications for health outcomes as a result of childhood growth experiences.
“Individuals who grow up in the context of socioeconomic adversity – even if they graduate from Northwestern...or in other ways become very upwardly mobile, compared to their peers who didn’t grew up in adversity – they will still be at a health disadvantage later in life," McDade said. "We don’t know exactly how that happens, but we think that epigenetic processes could be part of the ways in which our bodies remember, in a sense, those early experiences of adversity and shape our health later in life.”
Nonetheless, McDade also reminds readers that the relationship between socioeconomic status and epigenetics is just one factor in what contributes to health outcomes.
“[The findings don’t] mean that just because you may have grown up in poverty or with adversity that your genes are dysfunctional," McDade said. "There are lots of other things that you can do to help promote your health later in life, but [epigenetics] is a potentially important of the process in which early environments have a lasting effect on life later in life.”