Researchers analyzed cells that line the airway from healthy non-smokers and smokers with no detectable lung disease. The smokers' cells showed early signs of changes similar to those found in lung cancer.
"When you smoke a cigarette, some of the genetic programming of your lung cells is lost," senior investigator Dr Ronald Crystal, chairman and professor of genetic medicine at Weill Cornell Medical College in New York City, said in a college news release.
"Your cells take on the appearance of a more primitive cell. It doesn't necessarily mean you will develop cancer, but that the soil is fertile to develop cancer," he explained.
The results of the study, published July 16 in the journal Stem Cell, show that smoking causes harm, even when there is no clinical evidence that anything is wrong.
"The study doesn't say these people have cancer, but that the cells are already starting to lose control and become disordered," Crystal said. "The smoker thinks they are normal, and their doctor's exam is normal, but we know at the biologic level that all cigarette smokers' lungs are abnormal to some degree."
These very early changes can't be detected through physical examinations, lung function tests or X-rays. "The take-home message is: Don't smoke. Smoking is bad, and if you smoke, you're at risk," Crystal said.
Further research is needed to learn why smoking causes these changes. This could help scientists create treatments to prevent lung cancer.
The U.S. National Cancer Institute has more about lung cancer prevention.