Smoking woman
Smoking harms the DNA even after 30 years of quitting researchers from the Harvard Medical School in Massachusetts, US, revealed.Reuters

A smoker's DNA gets affected even 30 years after quitting smoking, a recent study has revealed. Smoking leaves its effects on the human body in the form of DNA methylation - a process by which cells regulates gene activity.

The study was conducted by researchers from Harvard Medical School. "Our study has found compelling evidence that smoking has a long-lasting impact on our molecular machinery, an impact that can last more than 30 years," said lead author Roby Joehanes.

It was observed that within a time span of five years, most of the DNA methylation sites of people who left smoking returned to the levels which are found in non-smokers. But some DNA methylation sites didn't return to that level even after 30 years of leaving smoking.

Heart stroke, cancer and chronic obstructive pulmonary disease are some long-term ailments which former smokers remain prone to despite quitting smoking long time back. The genes associated with various ailments such as cancer and heart diseases, which are caused by smoking, were mostly linked to methylation sites.

Around 16,000 participants were analysed in the study. The meta-analysis of DNA methylation sites was conducted across the genome and blood samples of the partakers were used. The team of researchers then compared the DNA methylation of people who never smoked with those who left smoking.

Smoking-associated DNA methylation sites were related to one-third of known human genes, which is equal to more than 7,000 genes.

"Some of these long-lasting methylation sites may be marking genes potentially important for former smokers who are still at increased risk of developing certain diseases," the researchers suggested.

DNA methylation could be crucial evidence which reveals the smoking history of a person and aid in providing researchers with important targets for coming up with new therapies.

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