Study Finds Smoking May Permanently Damage Genes

How harmful is smoking to the human body? U.S. researchers have found that smoking can damage genetic material. Although most genes can return to normal after quitting, some of the damage may last a lifetime. Roby Joehanes of Harvard Medical School said: “Our study provides strong evidence that smoking has a long-term impact on the body’s molecular mechanisms, lasting for more than 30 years.”

The research team analyzed blood samples from 16,000 participants across multiple studies conducted since 1971, along with questionnaires they completed about smoking, diet, lifestyle habits, and health history. They found methylation in more than 7,000 DNA sites among smokers. In other words, methylation affected about one-third of known human genes, many of which are associated with heart disease and cancer. Gene methylation can suppress gene expression and alter gene function.

The researchers also found that five years after quitting smoking, most methylated genes had recovered to the same state as those of people who had never smoked. However, 19 methylated genes, including the lymphoma-related TI-AM2 gene, had still not recovered even 30 years after quitting.