Active and Passive Smoking Linked to Breast Cancer

In many instances, strong or medium-strong connections have been shown to exist between breast cancer and various personal habits, lifestyle choices, genetic characteristics, and biological processes. When lists of risk factors for breast cancer are presented, they generally only include those factors that have been proven to a high degree of certainly to be linked to an increased incidence of the disease.

But what happens when the evidence is not so strong? Medical research has identified a number of factors that appear to have some connection to increased cancer risk, but the link is still not easy to establish for certain. This is usually because the amount of research done has been too limited, or because the apparent causal relationship is slight enough to cast doubt on the results. When situations like this arise, the most common approach is to mention the possible connection in passing, but to emphasize the fact that the causal link to the disease of the behavior, characteristic, or trait in question remains unproven.

One of the behaviors that falls into this category with respect to breast cancer is smoking. The connection between smoking and other types of conditions such as cancers of the lung, throat, and mouth are well-established. But with breast cancer the apparent link has seemed tenuous - many have speculated about a possible connection, but the evidence to prove it has been considered scanty and unimpressive.

In just the past few months, however, the picture has suddenly changed. The results of two new studies were released in 2011 that appear to show a noticeable and statistically significant relationship between smoking and an increased risk for breast cancer.

New Evidence
The first of these studies, released in January of 2011 and published in the Archives of Internal Medicine, has added important information to the debate about the connection between smoking and breast cancer. Researchers from Harvard were fortunate to have access to 30 years worth of data that had been collected about the health conditions and lifestyle patterns of over 110,000 women who participated in the massive and groundbreaking Nurses' Health Study. There were 8,772 cases of breast cancer diagnosed in this group during the period of time covered by the survey, and researchers looking at the data on the smoking habits of these women were careful to eliminate the possible influence of other risk factors before making their evaluation about the possible relationship between smoking and these cancers.

When all the numbers had been crunched, it was discovered that nurses in the study who smoked had increased their overall chances of contracting breast cancer by 6%. Relatively speaking, this is not a huge increase, and it would not qualify smoking as a strong causal factor for breast cancer. But among women who had smoked regularly for the entire period of the survey, the increased incidence  of breast cancer was a much more significant 28%.