Cigarette smoking changes the way certain genes are expressed, leading to an increased risk of cardiovascular diseases, inflammatory illnesses, and cancer, according to a study published recently in the journal Circulation: Cardiovascular Genetics.
An international team of researchers took blood samples from 15,907 people, including almost 9,000 current and former smokers and just under 7,000 non-smokers. Analyzing the DNA of each participant, the study authors began looking for statistically significant epigenetic differences between the three groups, and found that around 7,000 separate genes appear to be affected by smoking.
The term epigenetics refers to the ways in which genes are modified in order to alter their activation. A common modification occurs in the form of methylation, whereby methyl groups are added to DNA, changing the way that certain genes function.
While conducting their analysis, the researchers discovered major differences in DNA methylation between smokers and non-smokers, and noted that the majority of the genes affected are associated with the sorts of diseases normally attributed to smoking – namely cancer and pulmonary disorders.
Fortunately, the team found that once people stop smoking, most DNA methylation sites return to the sorts of levels seen in those who have never smoked. However, a small number of genes remain altered several decades after quitting smoking, suggesting that cigarette use may leave a permanent genetic footprint, resulting in a lifelong susceptibility to certain diseases.
“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 study co-author Roby Joehanes in a statement. “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.”