Poverty Is Stamped Into DNA in Childhood — And Stays There

A poorer upbringing increases people’s susceptibility to colds later in life, something they can’t shake even if they climb the socioeconomic ladder.

National Journal
Brian Resnick
Nov. 5, 2013, 9:04 a.m.

Poverty, it turns out, is etched in­to our DNA.

“For each de­crease of one year in par­ent­al home own­er­ship, the par­ti­cipants’ odds of de­vel­op­ing a cold in­creased by ap­prox­im­ately 9 per­cent.”

That’s not a meta­phor­ic­al state­ment. Grow­ing up poor leaves a per­man­ent mark on our per­man­ent ge­net­ic code, ac­cord­ing to new re­search.

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 (in this case, eco­nom­ic status), 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.”

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