While most of the DNA damage caused by smoking cigarettes can reverse itself within five years after quitting, findings of a new study have revealed that the habit may still leave lasting imprint on the DNA of smokers.
Researchers have found that while most of the damage caused by smoking to the DNA fades over time, changes in at least 19 genes can last for decades.
For the new study published in the journal Circulation: Cardiovascular Genetics on Sept. 20, researchers looked at the blood samples of 16,000 people who also provided information about their diet, lifestyle and smoking.
The researchers found that smokers have a pattern of methylation, changes in the DNA that can inactivate a gene or alter how it functions and this affects over 7,000 genes.
The researchers found that after people quit smoking, some of the DNA damage disappears within five years. Smoking-related changes in some genes, which include the TIAM2 gene associated with lymphoma, however, persisted 30 years later.
"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 study researcher Dr. Stephanie London, from the National Institute of Environmental Health Sciences.
London added that their findings show that even after a smoker stops smoking, the smoking-related effects on their DNA are still visible.
The researchers said that identifying smoking-related changes to the DNA can lead to the development of diagnostic tests that can more accurately assess the smoking history of a person.
While some of the affected genes are not linked to smoking-related damages, they can serve as markers to determine who have high risk of developing smoking-related diseases in the future. These may also help in the development of new drugs that can treat the damages caused by cigarette smoke.
"Many of the differentially methylated genes were novel genes with respect to biologic effects of smoking, and might represent therapeutic targets for prevention or treatment of tobacco-related diseases," London and colleagues wrote in their study.
The study provides another reason why people should not get started smoking in the first place.
"The message here is that smoking has an enormous, widespread impact on your genes," said American Lung Association senior scientific advisor Norman Edelman. "Most of it is reversible, but some is not. So if you smoke, you're going to alter your genetic makeup in a way that's not totally reversible."
