Smoking clearly damages human DNA, researchers found, and only some of the damage done will fade over time.
Researchers from the Harvard Medical School studied 16,000 people and discovered that while most disease-causing genetic effects from smoking may clear up in five years if smokers quit the habit, many remain in the human body for good.
These genetic marks are created in a process called methylation, wherein DNA is altered so that a gene can be inactivated or changed. Roby Joehanes of Harvard and Hebrew SeniorLife, says,
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.
Cancer and heart disease – two of the biggest causes of mortality in the United States – are caused by damage to genes. Some of these genetic anomalies are hereditary, but most come from lifestyle, with smoking one of the biggest negative factors, NBC News reports.
Joehanes points out, “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.”
The researchers analyzed blood samples from people that had participated in studies from as far back as 1971. The participants had filled out questionnaires on their diets, medical histories, smoking habits and general lifestyles.
Among the participants, the team found that smokers showed a pattern of methylation changes impacting over 7,000 genes – that’s one-third of all human genes. Many of these genes were closely associated with heart disease and cancers proven to likewise have been caused by smoking.
For those who quit smoking, most of the genetic changes reverted back to the same patterns seen in non-smokers after around five years, the researchers reported. However, in at least 19 genes, including the TIAM2 gene linked to lymphoma, remained for as long as 30 years.
Some of the genes the researchers observed had not been previously been linked to smoking. These could be used as markers to check on who are at higher risk for smoking-related diseases in the future, the researchers said. They could also be used to create new drugs to treat any damages caused by smoking.
The US Centers for Disease Control and Prevention reports that smoking is the foremost cause of preventable diseases, killing over 480,000 Americans yearly. The habit kills about 6 million people a year in related illnesses such as cancer, lung and heart diseases.
On the bright side, smoking seems to be on the decline in the USA, with only about 15% of adults and just 11% of teenagers reportedly smoking traditional cigarettes, while the rise in the use of electronic cigarettes, or vaping, continues.
The study was published in the American Heart Association journal Circulation: Cardiovascular Genetics.
