Can wearing a bra too long cause breast cancer? What about too tight?

With October ‘Breast Cancer Awareness Month’ comes the usual stories about breast cancer, tips on preventing the disease, and related topics. A perennial question that is asked almost every October is:

Does wearing a bra cause breast cancer?

If you have wondered if wearing a bra can cause breast cancer, you are not alone.

A 2014 study of 748 adults in Cork, Ireland, was conducted to test for knowledge of risk factors for breast cancer. Fully 29% of the participants believed that wearing a tight bra could increase breast cancer risk. A more recent study in February, 2019, of women in Brazil placed the risk of breast cancer from wearing an underwire bra at 58.5%! In this study, the younger you were, the more convinced that breast cancer could be caused by wearing a bra.

So let’s see where this notion came from and what the scientists say is true.

Where did the rumor that bras cause breast cancer come from?

The beginning of this theory was a one-two publication punch in the 90s.

First was a 1991 paper from the Harvard School of Public Health entitled, “Breast size, handedness, and breast cancer risk.” This paper described a study of about 15,000 women in which breast cup size and handedness (whether you wrote with your left or right hand) were related to breast cancer.

The strongest finding in the study was that, for premenopausal women, there was an association of increased breast size with increased cancer risk.

When the authors looked at whether women who got breast cancer wore a bra more frequently, they found a trend towards more cancer in these women. This trend was not big enough to be “statistically” significant however.

And the authors were careful to point out that the women who were more likely to wear a bra were also the ones with larger breasts and tended to be overweight. They said, “There was a suggestion that, among premenopausal women, those who did not wear a bra had a lower risk of breast cancer. The association, if real, could point to obesity or breast size as the relevant factor.”

This was followed in 1995 by the book, “Dressed to Kill: The Link Between Breast Cancer and Bras.” Here the authors, Sydney Ross Singer and Soma Grismaijer (a husband and wife medical anthropologist team) claimed that women who wore tight-fitting bras all day, every day, had a much higher risk of developing breast cancer than those who went au naturel. The authors claimed that by inhibiting lymphatic drainage, bras trapped toxins in the breast tissue, which caused cancer.

The problems with their theory are two-fold:

The authors’ observations that cultures where women did not wear bras also had a reduced cancer incidence did not take into account differences between these cultures in known risk factors for breast cancer, such as diet, weight, exercise, the age at which menstruation starts, pregnancies, and breast feeding.

The suggested mechanism is inconsistent with scientific concepts of breast physiology and pathology. The breast lymph system does not drain into the main part of the breast. The lymph system drains out of the breast into the underarm lymph nodes; and bras do not prevent the circulation of blood and lymph from the breast.

The authors’ proposal that bras block the lymphatic system which leads to accumulated toxins and cancer was likewise contradicted by scientific study. The National Institutes of Health examined cancer rates among women who had their underarm lymph nodes removed as part of melanoma treatment. The surgery, which is known to block lymph drainage from breast tissue, did not detectably increase breast cancer rates, the study found, meaning that it is extremely unlikely that wearing a bra, which affects lymph flow minimally if at all, would do so.

A final way to think about it is: well if wearing a bra causes breast cancer, then before the bra was “invented” breast cancer should be rare? Since the bra was patented in 1914 we can ask if breast cancer occurred before then. In fact breast cancer has been reported in every time period going back into the distant past. Princess Atossa was the first woman with a written report of breast cancer and that was in about 500 BC! So breast cancer was occurring long before women began to wear the bra.


What does the best science say?

To settle the question, a team of scientists from the Fred Hutchison Cancer Research Center, in Seattle, WA, conducted a careful study of the question. In a 2014 study entitled, “Bra wearing not associated with breast cancer risk: a population based case-control study,” about 1500 women, two-thirds with breast cancer and one-third without cancer, were asked about their bra wearing habits. This population-based case-control study found no evidence that any aspect of bra wearing is associated with risk of breast cancer. In particular the risk did not vary by daily duration of wearing a bra, age when women started wearing a bra, bra cup size, or whether women wore a bra with an underwire.

What do the experts say?

The National Cancer Institute (US) states that bras have not been shown to increase a woman’s risk of breast cancer.

The American Cancer Society states, “There are no scientifically valid studies that show wearing bras of any type causes breast cancer.”

The U.S. National Institutes of Health states, “Breast implants, using antiperspirants, and wearing underwire bras do not raise your risk for breast cancer.”

Why does the false theory of bras causing breast cancer persist?

It’s not clear why a theory that bras cause breast cancer, a theory that has been thoroughly disproven, persists. Perhaps it comes from the frustration of not knowing what causes the disease, coupled with a desire that the disease should come from the outside, from something a woman can control.

In any case, let’s stop worrying about breast cancer being caused by wearing a bra!

Steven Quay is the founder of Seattle-based Atossa Therapeutics Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company developing novel therapeutics and delivery methods for breast cancer and other breast conditions.

He received his M.D. and Ph.D. from The University of Michigan, was a postdoctoral fellow at MIT with Nobel Laureate H. Gobind Khorana, a resident at the Harvard-MGH Hospital, and was on the faculty of Stanford University School of Medicine. His contributions to medicine have been cited over 9,600 times. He has founded six startups, invented seven FDA-approved pharmaceuticals, and holds 87 US patents. Over 80 million people have benefited from the medicines he invented.

His current passion is the prevention of the two million yearly breast cancer cases worldwide.

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