This article is produced and financed by UiT The Arctic University of Norway - read more
Women who smoke have a higher risk of developing lung cancer compared to men
If a man and a woman smoke the same amount of cigarettes in their lives, the woman is at a greater risk of both getting lung cancer and dying from it.
It is well known that smoking is the leading cause of lung cancer, the most deadly form of cancer in the world. However, there has been uncertainty around whether there are differences between women and men when it comes to the risk of the disease.
Merethe Selnes Hansen has used data from around 600,000 Norwegian men and women in her PhD from UiT the Arctic University of Norway in order to answer this important question.
Greater risk than men
"We found that if women and men smoke the same amount throughout their lives, then women have a greater risk of getting lung cancer", says Selnes Hansen.
She is now back in her job as senior physician at the Department of Pulmonary Medicine at the University Hospital of Northern Norway (UNN).
"Men smoke more and longer than women", says Selnes Hansen.
Men have actually smoked 70 per cent of all cigarettes in Norway to date, according to the researcher.
But if you use statistical methods based on tobacco consumption where men and women have smoked the same amount and for the same length of time - and compare women and men - then women have a greater risk of getting lung cancer.
"One of the reasons for this may be that men have a greater chance of getting cardiovascular disease than women, and thus may become ill or die from other reasons than cancer", says Selnes Hansen.
In addition, there may be other factors that we do not know of.
Participants from several large studies
The 600,000 participants were recruited from all over Norway via three health surveys conducted between 1974-2003.
Selnes Hansen explains that at the time the participants replied to a questionnaire in which they answered questions about smoking status and other lifestyle factors such as physical activity.
The participants were then followed via their social security number, to determine whether or not they got lung cancer via the Cancer Registry, and emigration or death was registered via the National Population Register.
Of the 600,000 who participated in the study, there were 6,534 lung cancer cases, of which 43 percent were women, and 5,702 deaths from lung cancer, of which 42 percent were women.
The risk of death also higher for women
"We also found that women are at greater risk than men of actually dying from lung cancer. This may well be related to the fact that men have an increased risk of dying from other diseases, before they experience the result of lung cancer", says Selnes Hansen.
She explains that during the study, just over 40,000 men, and just over 30,000 women died for various reasons, so men have a higher risk of death overall, from many different diseases.
Research has shown that the lower your education, the more likely you are to smoke. The results of Selnes Hansen were consistent with what previous research has shown, namely that both women and men with lower education have a greater risk of getting lung cancer than those with medium or high education.
Lower education also leads to an increased risk of dying from lung cancer. Also among women, there is a significantly higher risk of dying from lung cancer if you have a lower education.
"The reason is most likely that those with lower education are also the ones who smoke the most", says Selnes Hansen.
She also says that those with low education have a greater chance of being exposed to passive smoking, air pollution, and other occupational risk factors that can contribute to lung cancer.
85% of cancer cases could have been avoided
Selnes Hansen also used data from The Norwegian Women and Cancer study (NOWAC), following 142,000 Norwegian women from all over Norway who were recruited between 1991 and 2007.
At the time of recruitment, the women received a questionnaire in which they answered questions about smoking status; such as how old they were when they started smoking, how many years they have smoked, how many cigarettes they smoke a day, whether they lived with someone who smoked as a child, and if they as adults live with someone who smokes.
"We found that in Norway, 85 per cent of lung cancer cases among women could have been avoided if the women did not smoke, so more than eight out of ten cases", Selnes Hansen says.
One thing is worth noting: those who actually continue to smoke are at the highest risk of developing lung cancer, if you compare with those who have smoked before but have now quit.
Quitting smoking pays
"Our study showed a clear relationship between how much and for how long you have smoked, and whether you stopped smoking or continued. Those who stopped smoking during the last 9 years had a 63 per cent lower chance of getting lung cancer compared to those who still smoke", says Selnes Hansen.
So it pays to quit smoking.
Selnes Hansen says that the strict tobacco regulation that has been in place in Norway has worked, as it has contributed to many people quitting smoking.
She believes that the results from her doctoral degree emphasize the importance of continuing strict tobacco campaigns. The researcher further believes that we should intensify anti-tobacco work and tobacco should become even more inaccessible and more expensive.
"It's about time that we stop selling tobacco along with milk and bread in regular grocery stores", concludes Selnes Hansen.
