Reviewing results from blood samples taken from nearly 16,000 people in 16 prior studies, the researchers also found that for those who stopped smoking, most genes “recovered” within five years of quitting.
“Although this emphasizes the long-term residual effects of smoking, the good news is the sooner you can stop smoking, the better off you are,” said study author Dr. Stephanie London. She is deputy chief of the epidemiology branch of the U.S. National Institute of Environmental Health Sciences.
Even so, London’s team found that some genetic changes remained, even 30 years after quitting smoking.
London and her colleagues zeroed in on a process called DNA methylation — genetic changes that don’t alter genes’ underlying code but can change how they’re expressed, or turned on.
Known to contribute to an array of health problems including cancer,heart disease and stroke, cigarette smoking remains the leading preventable cause of death worldwide, accounting for nearly 6 million deaths each year, according to the study.