Smoking may permanently damage DNA—an effect that could lead to the proliferation of life-threatening, smoking-related illnesses, according to a study published Tuesday in Circulation: Cardiovascular Genetics.
Researchers drew their results from a wide analysis of genome-wide DNA. They found that smoking had a significant effect on DNA methylation, a mechanism that impacts how genes are expressed, even years after an individual has stopped smoking.

But, encouragingly, researchers found that once a smoker kicks the habit, the majority of DNA methylation signals return to normal levels after five years, first study author Dr. Roby Joehanes, assistant scientist and medicine instructor at the department of medicine at Beth Israel Deaconess Medical Center and Harvard Medical School, said in the release.“These results are important because methylation, as one of the mechanisms of the regulation of gene expression, affects what genes are turned on, which has implications for the development of smoking-related diseases,” last study author Dr. Stephanie J. London, deputy chief of the epidemiology branch at the National Institute of Environmental Health Sciences at the National Institutes of Health, said in the release. “Equally important is our finding that even after someone stops smoking, we still see the effects of smoking on their DNA.” They found those effects lasted nearly 30 years.

“[This] means your body is trying to heal itself of the harmful impacts of tobacco smoking,”  he said.
Study authors said their findings are significant because knowing these DNA methylation sites may aid in the development of new treatments for smoking-related illnesses. Smoking remains the leading cause of preventable death worldwide, they noted.