Scientists have concluded that the effects of tobacco on your genes can still be seen even decades after you kick your cigarette habit
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You know that smoking is pretty much the worst thing you can do to your body-from the inside out, tobacco is just horrible for your health. But when someone quits the habit for good, just how much can they "undo" when it comes to those deadly side effects? Well, a new study published in an American Heart Association journal, Circulation: Cardiovascular Genetics, is shedding light on smoking's long-term footprint...and tbh, it's not great.

Researchers analyzed almost 16,000 blood samples from smokers, former smokers, and nonsmokers. They found that tobacco smoke was linked to damage to the surface of DNA-even for people who quit decades earlier.

"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 study author Roby Joehanes, Ph.D. The study specifically looked at DNA methylation, a process by which cells have some control over gene activity, in turn affecting how your genes function. This process is one such way in which tobacco exposure can predispose smokers to cancer, osteoporosis, and lung and cardiovascular diseases.

Although the results are disheartening, the study author said they see an upside to their findings: This new insight could help researchers develop treatments that target these affected genes and perhaps even prevent some smoking-related diseases.

In the U.S. alone, an estimated 40 million adults currently smoke cigarettes, according to CDC data from 2014. (We can only hope that number has continued to decrease since.) Cigarette smoking is also the leading cause of preventable disease and death-more than 16 million Americans live with a smoking-related disease. (Social smokers listen up: That Girls Night Out Cigarette Isn't a Harmless Habit.)

"Although this emphasizes the long-term residual effects of smoking, the good news is the sooner you can stop smoking, the better off you are," said study author Stephanie London, M.D., deputy chief of the National Institute of Environmental Health Sciences. Joehanes seconds that, explaining that once people quit, the majority of DNA sites in question returned to "'never smoker' levels after five years, which means your body is trying to heal itself of the harmful impacts of tobacco smoking."

Read: It's never too late to quit.