Smoking ‘leaves a footprint on your DNA, altering 7,000 genes linked to cancer and heart disease’
Scientists at Harvard found the change to a smoker's DNA can have an effect on their genes, which could increase the risk of chronic diseases
Smoking alters a person's DNA, leaving a footprint that could explain how lighting up increases a smoker's risk of developing cancer and heart disease.
A team of scientists believe tobacco smoke changes a chemical code on the DNA molecule that can sometimes change gene activity.
Some of these molecular changes revert to their original state when a smoker quits, but others persist in the long-term.
Experts have known for some time that smoking causes changes of the DNA molecule, but they are now learning more about how widespread the changes are, and what they may mean, said senior author Dr Stephanie London, from the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina.
“We don’t really know whether it means ‘damage’ to the DNA,” she told Reuters.
“That requires more study, using data outside what we have here.
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"What we’re saying is that it’s a change to your DNA that can have a downstream effect on what genes are expressed at what levels.”
The researchers combined data from 16 sets of participants in a previous study of ageing, totalling more than 15,000 people who had provided blood samples that were analysed for a type of DNA change known as methylation.
The DNA molecule contains instructions for growth and development in the form of genes, and so-called methyl groups along the molecule's surface - collections of hydrogen and carbon atoms - can determine which genes get activated.
The study team compared 2,433 current smokers - those who said they smoked at least once a day sometime over the last year - to 6,518 former smokers who had stopped at least one year before the blood draw and 6,596 never smokers.
Current smokers had 2,623 different methylated locations on their genes compared to never smokers.
That corresponds to 7,000 potentially affected genes, many of which are implicated in various cancers, high blood pressure and other health outcomes of smoking, said lead study author Roby Joehanes of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston.
But future studies will need to complete the chain from DNA changes to gene expression to disease outcome, he said.
Only 185 of the methylated locations were still significantly different between former smokers and never smokers, according to the results reported in Circulation: Cardiovascular Genetics.