Breast Cancer Risk is Lower among Obese Smoking Women

Smoking raises the risk of breast cancer, but the risk varies by obesity status in postmenopausal women, according to findings presented by the Women's Health Initiative observational study.

An important association between smoking and breast cancer risk was observed in skinny women, but not in obese women. The results were similar despite of whether obesity was characterized by body mass index (BMI) or waist line.

Juhua Luo, Ph.D., professor at West Virginia University, analyzed the relationship between obesity, smoking and breast cancer. Luo demonstrated these research results at the American Association for Cancer Research meeting, held April, 2.

“We found a connection between smoking and breast cancer risk among non-obese women, which is comprehensible because tobacco is a known carcinogen. However we didn’t depict the same connection between smoking and breast cancer risk among obese women. All those results were surprising,” Dr. Luo stated.

The study surveyed 76,628 women aged 50 to 79 years who did have previous history of cancer. All participants were part of the Women's Health Initiative observational study. They were recruited between 1993 and 1998 and supervised until 2009.

The level of obesity was measured by BMI and by waist-line, and the all results were fixed for other breast cancer risk factors.

The results of the research demonstrated that skinny women with a BMI less than 30 who have smoked, had a rather increased risk for breast cancer. Those who started to smoke at the age of 10-29 had a 16% excess risk; those with a 30- to 49 year history of smoking demonstrated a 25% excess risk; and those with 50 or more years of regular smoking showed a 62% excess risk. However, this same connection was not depicted among women with a BMI higher than 30.

Subsequently researches analyzed the findings according to waist-line in order to ascertain if the type of fat distribution – usually compared with central obesity – affected the results. When obesity status was defined by the waist-line higher than 88 cm, similar results were found.

Despite the research finding that smoking didn’t affect breast cancer risk among obese postmenopausal women, Luo underlined that she does not want to misinform public. Previous study has demonstrated that obesity alone is a risk factor for postmenopausal breast cancer.

“Smoking and obesity are among the main causes of death, both of which have essential consequences on health. This is only the first study to analyze the correlation between smoking, obesity and breast cancer risk. Probably one conclusion that can be made from this study is that more and more researches are needed in order to proof these results,” she concluded.