The authors said this is the first study to consider age at smoking initiation as a potential predictor of smoke-related DNA damage in former smokers. The research was funded by the National Cancer Institute, the National Institute of Environmental Health Sciences, the National Institutes of Health and the Department of Health and Human Services. If you quit smoking, the most significant factor in determining the damage level in the lung is the age you started to smoke, and not the amount or time that you smoked. In an editorial accompanying the study, researchers from the M.D. Anderson Cancer Center at the University of Texas in Houston said the new finding is one more piece in the lung cancer risk assessment puzzle. They said it is likely that multiple susceptibility factors have to be taken into account to fully understand interactions between the environment and genetics.
Cigarette smoking is the most important risk factor in lung cancer.
Some 171,600 new cases of lung cancer will be diagnosed in 1999, or 14 percent of all cancer diagnoses, according to the American Cancer Society. Wiencke said all smokers develop some DNA damage, a known risk factor for lung cancer, and all smokers who quit see some degree of DNA repair. The new study suggests that less repair or less successful repair occurs in people who smoked as adolescents. Wiencke said it appears that carcinogen chemicals called polynuclear aromatic hydrocarbons in cigarette tar attach themselves like a film over DNA, causing some cells to mutate. Lung tissue continues to develop until age 20, making younger smokers more susceptible to damage, he said.