Stress can leave damaging and lasting imprints on the genes of the urban poor.

This is according to a new study that claims poor people's DNA is declining in quality as a result of difficult upbringings.

The results are based on the finding that people in disadvantaged environments have shorter telomeres — DNA sequences that generally shrink with age — than their advantaged peers.

The study looked at the telomeres (pictured) of poor and lower middle-class black, white, and Mexican residents of Detroit. Telomeres are the protective caps on the ends of the strands of DNA called chromosomes, which house our genomes

WHAT ARE TELOMERES? Telomeres are the protective caps on the ends of the strands of DNA called chromosomes, which house our genomes. In young humans, telomeres are about 8,000-10,000 nucleotides long. They shorten with each cell division, however, and when they reach a critical length the cell stops dividing or dies. This internal 'clock' makes it difficult to keep most cells growing in a laboratory for more than a few cell doublings. Previous research has found telomere length can reliably predict life expectancy in humans. Advertisement

The study looked at the telomeres of poor and lower middle-class black, white, and Mexican residents of Detroit.

Telomeres are the protective caps on the ends of the strands of DNA called chromosomes, which house our genomes.

In young humans, telomeres are about 8,000-10,000 nucleotides long. They shorten with each cell division and as a result of stress.

Previous research has found telomere length can reliably predict life expectancy in humans.

The study found that low-income residents of Detroit, no matter their race, have shorter telomeres than the national average.

'There are effects of living in high-poverty, racially segregated neighbourhoods,' Dr Arline Geronimus, a visiting scholar at the Stanford Center for Advanced Study said in an interview with The Huffington Post.

Within this group, how race-ethnicity and income were associated with telomere length varied dramatically.

The shortest telomeres belonged to poor white people, while white Detroit residents who were lower-middle-class had the longest telomeres in the study.

Black residents had about the same telomere lengths regardless of their income level while poor Mexicans had longer telomeres than Mexicans with higher incomes.

Geronimus claims poor Mexicans in this study have longer telomeres than the non-poor Mexicans possibly because they grew up in less stressful environments.

Stress can leave damaging and lasting imprints on the genes of the urban poor. This is according to a new study that claims poor people's DNA is declining in quality at an alarming rate

'They come with a set of support systems and with a cultural orientation that doesn't undermine their sense of self-worth,' she said.

To explain the results of telomere length on the black population, the authors said: 'The separation between poor and non-poor black in everyday life is less marked than between poor and non-poor whites.'

The research follows a similar study by Princeton University and Pennsylvania State University last year which found stressful environments can impact the DNA of children as young as nine.

The study of 40 9-year-old black boys, published in the Proceedings of the National Academy of Sciences, showed that those who grow up in disadvantaged environments have shorter telomeres.

The researchers also reported that boys with genetic sensitivities to their environment have shorter telomeres after experiencing stressful social environments than the telomeres of boys without the genetic sensitivities.

These sensitivities are based on gene variants related to the serotonin and dopamine pathways — neurotransmitters essential for relaying information between the brain and body.

'I think it's very striking that these findings are in children at age nine, because you are talking about accelerated aging or stress-mediated wear and tear on your body, which make you more vulnerable to all kinds of illnesses and diseases,' said Geronimus of the previous study.