According to a recent study, smokers have a “footprint” of their addiction on their DNA. The DNA damage may be used to identify and develop treatments for smoking-related diseases such as cancer and cardiovascular disease.
The analysis took 16,000 blood samples from smokers, former smokers and nonsmokers. They found that tobacco smoke leaves a lasting impression of their addiction on the surface of their DNA. Even those that kicked the habit 30 years ago show changes in their genes.
This legacy appears as chemical changes to the surface of DNA. The changes affect how certain genes function, known as epigenetic changes.
The modification in this study was DNA methylation. DNA methylation is when a molecule referred to as a methyl group remains on the surface of DNA. It influences whether genes are silent or active. Studies show that smoking causes these surface changes to DNA. These changes could measure the risk of diseases, such as cancer.
However, the new study identifies the diversity of these genes, what genes are involved in someone’s risk of disease, and the strength of the association with smoking.
“The genes we found to be impacted were ones associated with smoking-related diseases,” she said.
Analyzing The Genome
To determine the difference in gene changes between smokers and nonsmokers, the researchers reviewed 15,907 blood samples from 16 groups of people and searched their genomes for sites that had methyl groups attached.
Over 2,600 areas were discovered by the team that showed a statistical difference between nonsmokers and smokers. This showed over 7,000 genes, equaling one-third of the known human genes.
Among people who had quit smoking within the last five years, the majority had returned to normal levels. However, some surface gene changes continue even 30 years after quitting. When comparing former smokers with nonsmokers, 185 of the 2,600 sites identified as different in smokers continued to show these chemical changes.
Smoking is the number one cause of preventable death worldwide. Despite a recent decline, nearly 17% of US adults report that they smoked in 2014, equaling 40 million adults.
Worldwide, over 1.1 billion people smoked in 2015, with 80% of them living in low to middle-income countries. Once someone quits, they continue to be at risk of developing an obstructive pulmonary disease, some cancers, and stroke.
The team believes their new findings mean the smoking history of an individual could be revealed by the use of testing DNA. This knowledge will help researchers view risk factors for diseases like lung cancer and heart disease. “These would be useful to identify the effects of smoking in (other) studies,” said London.
Understanding these gene changes also provides the opportunity to develop and target new cures.
“We identified many genes affected by smoking,” London said, adding that new therapies could target these genes to prevent smoking-related diseases. “(If) we understand what smoking does, we can potentially intervene.”
Some experts believe the findings will remind people of how harmful smoking can be.
“It further emphasizes the point that while giving up smoking is a very important way to reduce the risk of serious disease, it is even better not to start at all,” said Jeremy Pearson, associate medical director at the British Heart Foundation said.