Smoking is associated with three of every ten cancer deaths. Eight of every ten lung cancer deaths in men and just under that in women are due to smoking. Other cancers associated with smoking include cancers of the head and neck region, bladder, kidney and pancreatic cancers. Smoking has been implicated in leukaemia and in the development of polyps in the large bowel.
Although we tend to focus on smoking and cancer, just as deadly are the heart disease, airways disease and strokes which are more likely in tobacco smokers. It has been estimated that one in every four smokers dies as a result of smoking. Those who smoke more than twenty cigarettes every day reduce their lifespan by around fifteen years as compared with non-smokers.
The good news is that if you give up cigarette smoking there is a gradual fall in your risk of death from lung cancer. This does not happen immediately and the risk may be higher than for non-smokers for as long as 25 years. Giving up smoking at a younger age has more impact on reducing the risk of cancer than if you wait until you are older. The benefit in reducing the risk of heart disease becomes apparent more quickly, possibly by one year.
Smoking, unfortunately, does not impact only on the smoker. Probably two-thirds of the smoke from a cigarette goes into the atmosphere and can affect those around the smoker. So-called passive smoking has been more difficult to isolate as a risk factor for cancer. Certainly, breakdown products from tobacco smoke can be measured in the bodies of the partners of smokers. They may have about one-third higher risk of lung cancer than non-smokers.
Why does smoking cause cancer? Cigarette smoke contains chemical carcinogens. These chemicals can promote cancer by causing mutations in the cells’ genes. Although we are talking here about environmental causes of cancer, there are inherited factors that determine whether a person can break down these cancer-causing chemicals. Indeed, some people can inherit the ability to activate these carcinogens. These chemicals will ultimately cause changes in the genes which may add to other inherited or acquired changes over time and eventually promote the development of cancer. Many gene mutations have been found to be associated with lung cancers.
Whether cancer results from exposure to these carcinogens may depend on whether the cell can repair the damage in time. The rate of repair is another factor that can be inherited. Therefore, some people who smoke will be more prone to developing cancer than others, depending on what tendencies they have inherited. The fact that an individual lives a full life span despite smoking heavily is his good genetic fortune, rather than support for claims that cigarette smoking does not cause cancer.