Poverty can leave a mark on our DNA

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A team at Northwestern University, Illinois, USA, have announced that experience of poverty can leave a mark on a person’s DNA, specifically in the epigenetics of their genome.

Poverty, discussed here as a low socioeconomic status (SES), has long been associated with poor health and reduced life expectancy. This has been used in practice, with low educational attainment and/or income level, to predict increased risk of heart disease, diabetes, cancers, and infectious diseases.

The relationship between low SES and poor health has frequently been blamed on the people it affects by the insinuation that they’re stereotypically poorer lifestyles is the cause of poor health. Part of this stereotype includes the preconceptions that poor health may be caused by consumption of nutritionally poor food, increased smoking and alcohol use, and leading a more sedentary lifestyle.

Misconceptions and stereotypes appear to have meant that the poor health experienced by those in poverty is not often discussed as a public health issue. One factor not usually attributed to the individual is that in some parts of the world they might have limited access to information and basic healthcare.

A 2017 Lancet study by the Imperial College, London, reported that low SES has almost the same impact on health as smoking or a sedentary lifestyle and is associated with a reduction in life expectancy of 2.1 years. This reduction in life expectancy among people living in poverty may be caused by infectious disease, which the charity Health Poverty Action reports is prevalent in communities with high levels of poverty. Other conditions which may reduce life expectancy include cancers, heart disease, and diabetes, among others.

Misconceptions and stereotypes appear to have meant that the poor health experienced by those in poverty is not often discussed as a public health issue

These conditions and others like them may be the cause of death and ill health, but the research being done is implying that the conditions affect people living in poverty more than those who don’t because they are living in poverty. This is what makes low SES a public health issue, because it may be making people more susceptible to these conditions.

New research by a team at Northwestern University have linked the effects of low SES to changes to the DNA caused by DNA methylation, a process often referred to as epigenetics. This may shed some light on how low SES promotes life-limiting conditions and poor health.

DNA methylation is a mechanism used in all cells to alter gene expression, meaning whether or not a gene is transcribed and used by the cell. Methylation is the addition of a methyl group to a cytosine base in the DNA code. This addition blocks transcription machinery from making a copy of the DNA which would be then used to make whatever that gene encodes. By blocking this process, the gene in question is essentially ‘turned off’.

[…] the research being done is implying that the conditions affect people living in poverty more than those who don’t because they are living in poverty. This is what makes low SES a public health issue, because it may be making people more susceptible to these conditions

Healthy cells do this for efficiency. For example, liver cells and brain cells are vastly different in function, and therefore use a different set of genes to carry out their functions. For efficiency, they ‘turn off’ the genes they don’t need to use. This leaves these stretches of DNA intact, but dormant.

Epigenetics may be implicated in the link between low SES and poor health because the team discovered an association between levels of methylation at more than 2,500 sites across over 1500 genes. This is consistent with a wide range of biological systems known to be altered by low SES, including chronic inflammation, insulin resistance and cortisol deregulation. These changes to the DNA may predispose the person to conditions which can reduce quality of life or life expectancy.

This is an important finding in terms of solving the mechanism by which low SES may cause poor health, but it does not explain why these elements in the genome are affected. What it does show is that people living in poverty may be set up for long term effects, because of something they have little control over. People do not choose to live in poverty but their experience can be improved with systemic change. As Dr Silvia Stringhini argued with the Lancet (2017) paper, this data should be used to urge governments to take action to combat poverty and to take steps to prevent this from happening in the genomes of future generations.

Thomas McDade, the lead author of the paper published in the American Journal of Physical Anthropology, said that there “is no nature vs nurture.” They impact each other. If methylation is a mechanism by which low SES impacts health, it is something out of the control of the person, because poverty is not a choice.

As Dr Silvia Stringhini argued with the Lancet (2017) paper, this data should be used to urge governments to take action to combat poverty and to take steps to prevent this from happening in the genomes of future generations

This study is not conclusive and follow-up work is required to determine the health consequences of methylation at sites researchers have identified. Many of the sites already identified are associated with processes related to immune responses to infection, skeletal development, and development of the nervous system. These have the potential to further contribute to poor health.

This post was written by Molly Eastol and edited by Karolina Zieba.

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