The discovery adds to a growing weight of evidence linking exposure to tobacco smoke with the disease.
The results held true even after accounting for alcohol consumption, which is a breast cancer risk factor that is more common among smokers. In the International Agency for Research on Cancer concluded there was "limited evidence" that smoking tobacco could trigger breast cancer.
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But in the last few years findings have led to a U-turn in expert opinion. 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, 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.
More work is now needed to understand the mechanisms behind the link between smoking and breast cancer in post-menopausal women.
Smoking is the biggest preventable cause of cancer worldwide. The habit is linked not only to lung cancer but cancers of the larynx, oesophagus, hasnyálmirigy cukorbetegseg cavity, pharynx, bladder, pancreas, kidney, liver, stomach and bowel.
In the past 50 years, it is estimated that 6. Dr Julie Sharp, head of health information at Cancer Research UK, which owns the British Journal of Cancer, said: "Evidence remains inconsistent as to whether smoking causes breast cancer after as well as before the menopause, but this study suggests it may increase a post-menopausal woman's risk of breast cancer if she smokes or has smoked in the past.