Poverty, it turns out, is etched into our DNA.
That's not a metaphorical statement. Growing up poor leaves a permanent mark on our permanent genetic code, according to new research.
"For each decrease of one year in parental home ownership, the participants' odds of developing a cold increased by approximately 9 percent."
Socioeconomic status during childhood correlates with shorter sections of DNA, known as telomeres, later in life, explains a study published in the November issue of the journal Brain, Behavior, and Immunity. Telomeres are the caps to a strand of DNA and, like a case covering an external hard drive, they protect the internal data from corrosion. Without getting too deep into the science, the length of the telomere is a rough indicator of the age and health of a human cell. Every time a cell splits into two, the telomere is slightly shortened. So DNA degrades as it divides. It's a component of human aging. It's also the reason why cloned animals like Dolly the sheep don't live as long as the originals—you make a baby animal with old DNA, and it ages faster.
More broadly, the telomere "is a marker of the functionality of certain immune cells," lead researcher Sheldon Cohen says. "The shorter these telomeres, the less functional these immune cells are. " And somehow poverty is inscribing itself on the code of mankind.
Cohen's study found that for each year a person spent living in a home their parents didn't own (a rough, yet relatively reliable indicator of socioeconomic status), the telomere length decreased by 5 percent.
And what can be seen under the microscope is reflected in daily life. In the study, participants were asked to take a dose of a cold virus (apparently, to get people to agree to get sick for science, you have to offer them $1,000 for their efforts). Those who indicated a lower socioeconomic status as a child were more likely to be infected by the virus and show symptoms. "For each decrease of one year in parental home ownership, the participants' odds of developing a cold increased by approximately 9 percent," the study concluded.
Cohen explains that in research regarding cold outcomes, scientists must measure whether a person was infected by the disease in the first place, and then measure that person's immune response to the disease. It's rare for both systems to be affected by the same variable, Cohen says. But that's what is happening here.
"And we virtually never find that," Cohen says.
Cohen says the research hasn't found anything more specific than socioeconomic status during childhood to correlate with these health outcomes. That is, he and his team tried to control for factors like divorce, home stability, the likelihood of people of low socioeconomic status smoking or drinking later in life, body mass index, and so on. No other variable correlated with decreased telomere length or cold outcomes.
There are many ways poverty could affect the human body—limited access to health care, a more stressful home environment, a more violent neighborhood, and poorer nutrition can all lead to poor health outcomes. "Whatever it is," Cohen says of the exact mechanism, "it is having a big effect and it is having a broad effect on the biological system." And improving someone's placement on the socioeconomic ladder would not reverse the changes children low on the rungs experienced while growing up. The effects held no matter how well-off people became in adulthood.
A 2009 study from the National Institutes of Health found that psychological stress and trauma in youth can translate to lower telomere length later on. "Both emotional neglect and physical neglect were linked to shorter telomeres," the paper concluded, "thus it is possible that in addition to the psychological effects of stress, physical stressors such as inadequate nutrition or illness contributed to the findings."
If all this seems kind of bleak—that poor children have a biological inequality etched into their cells that they can't get rid of—well, it is—for now. Cohen calls the data preliminary, and his research field will work in the future to determine which variables, if any, variable can intervene in the process. (Other researchers working on this question have found inconclusive evidence that socioeconomic status decreased telomere length—though that study didn't use parental home ownership as its self-selecting variable.)
While DNA provides the framework to our lives, our experiences can dictate how that frame fills in. Take language learning as a similar concept. There's the oft-reported "30 million word gap" study, which found that children in wealthier homes know hundreds more words than children growing up in families that receive welfare benefits. This disconnect causes a gap in language and learning development that widens further when children start school.
The language acquisition is a different process, but it tells a similar story about the impact of environment.
Cohen sums it up: "Trajectories are set in childhood and at least are not easily susceptible for change."