Smoking Cigarettes Can Alter DNA for Decades

Smoking may alter your DNA decades after quitting, says the American Heart Association. According to the study published in Circulation: Cardiovascular Genetics, smoking directly impacts the human genome, which includes the entire genetic makeup in a person. This is done through DNA methylation, a process where cells change the gene’s functions and activity. “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 J. London, deputy chief of Epidemiology at the National Institute of Health Sciences. London is also credited as an author on the study. THE STUDY Researchers took blood samples from around 16,000 subjects, and compared the DNA of long-term smokers to lifelong non-smokers. They discovered that DNA methylation sites in smokers were linked to over 7,000 genes. That is one third of all known human genes. “Equally important is our finding that even after someone stops smoking, we still see the effects of smoking on their DNA,” London added. For the most part, results suggest that DNA methylation sites in previous smokers returned to the levels of a non-smoker within five years of quitting. However, researchers note that some methylation sites stayed three decades past an individual’s quit date. The genes affected could even lead to the development and diagnosis of smoking-related diseases like cardiovascular disease, pulmonary disease, cancer and stroke. TOBACCO USE IN THE UNITED STATES Currently, around 45 million adults smoke cigarettes in the United States. According to the American Cancer Society, tobacco use is still the leading cause of preventable disease and early death. One out of every two smokers will die from a tobacco-related illness. Researchers did find hope for those who quit smoking. “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,” said Roby Joehanes, a Ph.D. from Harvard Medical School. THE DECLINE OF SMOKING The percentage of smokers in America has steadily declined since the mid 1960s. In 1965, 42 percent of the nation regularly smoked cigarettes. Today, it has dropped to 15 percent – a significant change in half a century. Tom Frieden, director of the Center for Disease Control, believes there is still room for improvement. “There’s still far too many adults and kids using tobacco, but this is real progress,” Frieden said, “Tobacco remains the leading preventable cause of death in this country. It continues to kill nearly half a million people per year. And we have much further to go to help smokers quit and to reduce the number of kids who get addicted every day.”