(RxWiki News) Smoking increases the risk of getting many kinds of cancers. In the case of breast cancer, smoking combined with other factors can make that risk much greater.
The association between smoking and breast cancer has been difficult to sort out because of other factors that may be at play. Alcohol use, weight, family history and reproductive history have all been identified as additional factors that could increase the risk of getting breast cancer even more in smokers.
A recent study found that smokers had an increased risk of postmenopausal breast cancer — a risk that was even higher in smokers without a family history of breast cancer or those who began having periods on or after age 15.
"Talk to your doctor about ways to quit smoking."
This research team was led by Dr. Sarah J. Nyante, from the Division of Cancer Epidemiology and Genetics at the National Cancer Institute in Bethesda, MD.
Dr. Nyante’s team used information collected on 186,150 women who participated in the NIH-AARP Diet and Health Study.
From 1995 to 1996, the women in the study, aged 50 to 71, had completed a health and nutrition questionnaire. The questionnaire asked whether the women were current, former or never smokers, the amount of exercise they got, about their alcohol use and reproductive history.
The research team collected information on cases of breast cancer in the women for over nine years. They analyzed the association of factors on the questionnaire with the risk of postmenopausal breast cancer.
The results showed a 19 percent increase in risk of postmenopausal breast cancer in women who smoked and a 7 percent increase in women who used to smoke, compared to never smokers.
The risk of postmenopausal breast cancer was increased further in women who were smokers and did not have a family history of breast cancer. The risk in these women was 24 percent higher than in those who smoked and did have a family history of breast cancer.
Smokers who started having periods at age 15 or older had a 52 percent higher risk of postmenopausal cancer than women who started having periods at age 12 or younger.
The researchers found no clear relationship between the number of cigarettes smoked per day and the risk for breast cancer.
No association was found between alcohol consumption and the risk for postmenopausal breast cancer.
The authors noted some limitations of their research. Since the participants were not asked how long they had been smoking on the first questionnaire, the researchers could not relate the effect of the number of smoking years on breast cancer risk. They also had incomplete information on the types of breast cancer the women had, so this association could not be evaluated.
The authors commented that additional studies to determine the genetic effects of smoking and the effects of smoking on breast tissue during different stages of development might help expand the understanding of their results.
This research appeared in the March issue of the British Journal of Cancer.
Funding for this study was provided by the National Cancer Institute.
The researchers disclosed no conflicts of interest.