There's a significant link between smoking and breast cancer risk in postmenopausal women, but it depends on their body weight, researchers report.
Breast cancer risk was higher than normal among female smokers who were not obese, but this strong association was not evident in obese female smokers, according to a new study.
Researchers analysed data from 76,628 women, aged 50 to 79, who had no previous history of cancer. They were participants in the Women's Health Initiative study and were recruited between 1993 and 1998 and followed until 2009.
Non-obese smokers with a body-mass index (BMI) of less than 30 had a significantly increased risk of cancer compared to nonsmokers. Those who smoked for 10 to 29 years had a 16% higher risk, those who smoked for 30 to 49 years had a 25% increased risk, and those who smoked for 50 years or more had a 62% greater risk.
But obese women who smoked didn't appear to be at increased risk for breast cancer.
Obesity still a risk despite findings
"We found an association between smoking and breast cancer risk among non-obese women, which is understandable because tobacco is known carcinogen. However, we did not find the same association between smoking and breast cancer risk among obese women. This result was surprising," Juhua Luo, an assistant professor in the department of community medicine at West Virginia University, said.
People should not take the wrong message from these findings, said Luo, who emphasised that previous research has shown that obesity alone is a risk factor for breast cancer in postmenopausal women.
"This is only the first study to examine the interaction between smoking, obesity and breast cancer risk. The main conclusion from this research is that more studies are needed to confirm these results," Luo said.
Since the findings are to be presented at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.
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