11.01am
LONDON - Women who start smoking when they are teenagers are 70 per cent more likely to develop breast cancer than non-smokers, say Canadian scientists.
But those who take up the habit later in life, after their first pregnancy, have a reduced chance of suffering from the illness.
Dr Pierre Band of
Health Canada in Quebec and colleagues from the British Columbia Cancer Agency in Vancouver questioned 2000 women, with and without breast cancer, in a survey to determine the impact of smoking on the risk of the disease.
About 1400 women had gone through the menopause and the others had not.
"Our results suggest that cigarette smoke exerts a dual action on the breast, with different effects in premenopausal and post menopausal women," Band said in the research published in The Lancet medical journal.
The scientists found that in younger women the risk of breast cancer increases if they start smoking within five years of puberty.
But in older women, smoking does not increase the chances of suffering from the disease regardless of when smoking starts. They found a reduced risk in women who took up the habit after their first pregnancy.
Band and his team believe that breast cancer tissue could be particularly sensitive to cancer-causing agents during puberty when the breasts are developing.
"Our observations reinforce the importance of smoking prevention, especially in early adolescence," he said.
But Dr Stephen Duffy of the charity Cancer Research UK said the impact of smoking on breast cancer risk was still unclear and further research was needed.
"This study suggests an increased risk of breast cancer for women who smoke in their teens and a decreased risk of the disease for women who take up smoking later in life, after their first pregnancy. Both of these could be chance findings since the study is relatively small," Duffy said in a statement.
He added that the overall effect of smoking on the risk of other illnesses such as heart disease, respiratory problems and lung and other cancers by far outweigh any possible protective effect.
Further reading
nzherald.co.nz/health
