The genes in the cells of the lining of your airways are altered for a long time if you are a smoker, the tumor suppressor genes (the ones that protect you from cancer) are altered for much longer than we had thought. This probably means that an ex-smoker may be at a much higher risk of developing lung cancer for quite a long time.

In this new study, led by Dr. Avrum Spira, Boston University Medical School, genes normally expressed in airways cells were identified. The team then observed how smoking altered gene expression in those cells. They then looked at whether the changes could be reversed if the person gave up smoking.

They found that smokers had a 97% change in the way their genes were expressed in comparison to non-smokers (people who had never smoked).

You can read about this study in The Proceedings of the National Academy of Sciences.

They found that the 97% figure went down the longer the person had given up. However, they also found that 13 genes did not go back to normal after a smoker had given up, even if that smoker had given up 30 years ago.

The bad news for the ex-smoker is that among those 13 genes are some tumor-suppressor genes - those genes seemed to be permanently suppressed. Other oncogenes were permanently increased. Oncogenes are cancer-related genes (not good ones).

The researchers also went on to say that gene testing of airway cells may help us to identify those who are more likely to develop lung cancer (cancer in the airways).