Study: Smoking can permanently damage DNA

A new study published Tuesday finds that most DNA damage caused by smoking reverses itself five years after a person quits, but changes in at least 19 genes can last decades.

The team studied 16,000 people, with some participating in studies as far back as 1971. They supplied blood samples, shared their health histories, and filled out questionnaires regarding smoking, diet, and lifestyle. Researchers discovered that smokers had a pattern of methylation, an alteration of DNA that can change how a gene functions, affecting more than 7,000 genes. While researchers found that after people quit, most of the DNA damage disappears after five years, some genes, including the TIAM2 gene linked to lymphoma, still had changes caused by smoking 30 years later.

"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," Roby Joehanes of Hebrew SeniorLife and Harvard Medical School told NBC News. "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." Writing in the journal Circulation: Cardiovascular Genetics, researchers said that by finding affected genes not previously associated with smoking, they could be used to determine who is at risk of developing diseases caused by smoking in the future. They could also be used to create new drugs to treat damage caused by cigarette smoke. Every year, more than 480,000 Americans are killed by smoking, the Centers for Disease Control and Prevention says.

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