Smoking May Cause Permanent DNA Damage: Study

It has been known for decades that smoking is bad for the health, but new research suggests that while some damage may be reversible, smoking may permanently damage DNA. 

In a study published this week by the American Heart Association, in the medical journal Circulation: Cardiovascular Genetics, researchers note that smoking affects the DNA of more than 7,000 human genes. Most of the damage to the genes from smoking healed after five years, but at least 19 genes were scarred permanently.

Researchers conducted an analysis of nearly 16,000 samples of DNA. The blood samples were taken from participants in 16 studies. It included more than 2,400 current smokers, 6,500 former smokers and nearly 7,000 people who never smoked. The studies went back to 1971.

Samples of blood were taken from participants. They also filled out questionnaires about their diet, smoking habits, lifestyles and heart history.

The study indicated smoking caused a pattern of persistent altered methylation, or scarring of the DNA. Methylation marks DNA and can change how it functions, activating diseases and other illness, such as cancer.

The scarring affected more than 7,000 genes, or one-third of known human genes.

Researchers determined most of the damage to the DNA faded over time, within about four years for most people if they quit smoking. However, not all of the damage from smoking was reversed.

“Cigarette smoking has a broad impact on genome-wide methylation that, at many loci, persists many years after smoking cessation,” wrote study authors.

In 19 genes, smoking caused permanent damage. Many of the genes affected are genes with known links to heart disease and cancer. The TIAM2 gene is linked to lymphoma, and the damage to that gene can last more than 30 years.

Many diseases have a genetic basis, but can be triggered by daily habits that affect health, including smoking. However, once a person stops smoking the methylation begins to stop and after five years genes can return to the healthy levels seen in a person who has never smoked. It’s one of the many ways the body attempts to heal itself.

Experts say smoking causes more preventable illnesses than any other substance or habit. More than 480,000 American’s die every year from smoking related illnesses, according to the U.S. Centers for Disease Control and Prevention. More than 6 million people are killed globally from smoking, after getting cancer, heart disease and lung disease each year.

Despite the recent drops in smoking rates, about 15 percent of adults in the U.S. smoke and 11 percent of high school students. A large portion of the population is still at risk of permanent DNA damage and future disease as a result.