(NBC News/Maggie Fox) — Smoking changes DNA in clear patterns,researchers reported Tuesday. Most of the damage fades over time, they found — but not all of it.
Their study of 16,000 people found that while most of the genetic footprints left by smoking fade after five years if people quit, some appear to stay there forever.
The marks are made in a process called methylation, which is an alteration of DNA that can inactivate a gene or change how it functions.
"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 Roby Joehanes of Hebrew SeniorLife and Harvard Medical School.
"The encouraging news is that once you stop smoking, the majority of DNA methylation signals return to never-smoker levels after five years, which means your body is trying to heal itself of the harmful impacts of tobacco smoking," Joehanes said.
The team examined blood samples given by 16,000 people taking part in various studies going back to 1971. In all the studies, people have given blood samples and filled out questionnaires about smoking, diet, lifestyle and their health histories.
They found smokers had a pattern of methylation changes affecting more than 7,000 genes, or one-third of known human genes. Many of the genes had known links to heart disease and cancers known to be caused by smoking.
Among quitters, most of these changes reverted to the patterns seen in people who never smoked after about five years, the team reported in the American Heart Association journal Circulation: Cardiovascular Genetics.
But smoking-related changes in 19 genes, including the TIAM2 gene linked to lymphoma, lasted 30 years, the team found.
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