Cigarette Smoke Can Permanently Damage Your DNA

Smoking may have a longer, more harmful impact on your health than previously thought. In fact, it can permanently damage a person’s DNA, according to a new study.

Scientists examined blood samples given by 16,000 people dating back to 1971. They found that a lot of the harmful, disease-causing genetic changes done by smoking faded after five years, but some of them stayed in the DNA forever.

“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 study found that smoking a pack a day can cause about 333 DNA mutations per year, and only about 150 of those mutations are in the lungs. The rest spread to the larynx, pharynx, mouth, bladder, and liver. Most of the mutations are not dangerous, but smokers are essentially playing a game of Russian Roulette with each puff, triggering an avalanche of gene damage that could potentially lead to cancer.

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Researchers found that smokers had a pattern of methylation changes to over 7,000 genes, and many of those impacted genes were linked to heart disease and cancer. Methylation changes are alterations to the DNA that can change how a gene functions.

“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,” said Dr. Stephanie London of the National Institute of Environmental Health Sciences, who directed the team. “Equally important is our finding that even after someone stops smoking, we still see the effects of smoking on their DNA.”

Many of those genetic changes were reversed within five years of quitting smoking. However, about 19 smoking-related changes in the genes, such as the gene linked to lymphoma, lasted 30 years, according to the study.

“If you smoke four to five packs of cigarettes in your lifetime, it doesn’t sound that much, but you still get several mutations in every cell in your lungs, and these are permanent, they do not go away,” said Ludmil Alexandrov, a theoretical biologist at Los Alamos National Lab in New Mexico and the first author of the study. “There are a lot of things that do revert back when you stop smoking, and this shouldn’t discourage people from giving up, but the specific mutations in the lung cells are like scars. If you stop smoking, they’ll still be there.”

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By studying the impact smoking has on DNA, scientists may be able to create new drugs that can specifically target genetic damage done by cigarette smoke.

Smoking remains one of the leading causes of preventable illness, and kills more than 480,000 Americans each year, according to the Centers for Disease Control and Prevention. Internationally, smoking-related illnesses such as cancer and heart disease kill about 6 million people a year.