Study published in British Journal of Cancer found women who used to smoke were still 7% more at risk of disease
Smoking increases the risk of breast cancer in older women by almost a fifth, a study has found. The discovery adds to a growing weight of evidence linking exposure to tobacco smoke with the disease.
US scientists who tracked the progress of around 186,000 women aged 50 to 71 found that those who smoked were 19% more likely to develop breast cancer than those who had never smoked. Women who once smoked but then kicked the habit were still 7% more at risk.
The results held true even after accounting for alcohol consumption, which is a breast cancer risk factor that is more common among smokers.
In 2009 the International Agency for Research on Cancer concluded there was “limited evidence” that smoking tobacco could trigger breast cancer. But in the last few years findings have led to a U-turn in expert opinion.
Last year, researchers from the American Cancer Society reported results showing a 24% higher rate of breast cancer among women who smoked.
The risk was much greater among those who started smoking young, either before they started menstruating or before having their first child.
The new study, published in the British Journal of Cancer, covered a period of around 10 years. During this time, 7,500 of the women were diagnosed with breast cancer.
Dr Sarah Nyante, from the US National Cancer Institute in Bethesda, Maryland, said: “Our study adds to a growing body of evidence that suggests an association between cigarette smoking and increased breast cancer risk.
“Previous studies have investigated this relationship, but questions remained regarding the extent to which other breast cancer risk factors, such as alcohol intake, might influence the results. More work is now needed to understand the mechanisms behind the link between smoking and breast cancer in post-menopausal women.”
While other lifestyle factors such as being overweight, drinking alcohol and lack of exercise are all known to increase breast cancer risk in post-menopausal women, the role of smoking has been more difficult to unravel.
Smoking is the biggest preventable cause of cancer worldwide. The habit is linked not only to lung cancer but cancers of the larynx, oesophagus, oral cavity, pharynx, bladder, pancreas, kidney, liver, stomach and bowel.