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So Much For The Killer Bra: Study Finds No Link With Breast Cancer

If you're a bra-wearing woman, maybe you know this feeling: You exhale with relief as you unhook your band at the end of a long day. Looking over your shoulder into the mirror, you see the slight indentation the elastic has left on your torso, and think: "Constriction like this just can't be good."

That intuition resonates with popular theorizing that bras can lead to breast cancer by blocking the healthy drainage of waste products from the breast area. Hence the higher breast cancer rates in developed countries.

But give me good hard data over feelings and pop theories every time. A big new study, funded by the National Cancer Institute, finds no link at all between bras and breast cancer.

The study, published in the journal "Cancer Epidemiology, Biomarkers & Prevention," found that whether women wear bras just a few hours a day or more than 16, whether they wear underwires or wireless, whether they have big cups or small cups, brassieres are guiltless: They just do not seem to be linked to the two most common forms of breast cancer.

The research involved hundreds of postmenopausal women: 454 with invasive ductal carcinoma, 590 with invasive lobular carcinoma, and 469 without breast cancer, who served as controls. Each woman answered questions about everything from her pregnancy history to the age at which she started wearing a bra, whether it had an underwire, cup size, band size and how many hours a day she wore it.

Bottom line: It looks like your bra won't kill you unless someone strangles you with it. Which contradicts a 1995 book that added gallons of fuel to the theory that bras are harmful: "Dressed To Kill: The Link Between Breast Cancer and Bras."

The new paper's senior author, Dr. Christopher Li, head of the Translational Research Program at the Fred Hutchinson Cancer Research Center, says "Dressed To Kill" provided some of the impetus for the study. Our conversation, lightly edited:

Why did you think this study was worth doing?

The whole theory about bra-wearing and breast cancer came to my attention years ago, when there was this book published called "Dressed to Kill." The whole premise of the book was that bra-wearing is the primary culprit for breast cancer in the world. Being a breast cancer researcher, I had never heard of this theory, and people, friends of mine who had seen it, were saying, 'What's going on with this?'

I thought I should look into the scientific literature and see what there was on this topic, and I was very surprised to see there was not a single paper focused on it. At the time, we were designing a study looking at some other questions, and I thought well, we could add a few questions about this to our study and at least maybe try to get some answers about it. So it certainly wasn’t the main focus of what we were trying to do, but we thought it was a reasonable thing to add on to a larger study to try to at least get some answers. Because breast cancer is obviously of considerable public health important, bra-wearing is a ubiquitous practice, so if there really is a link — there's this clear gap in the literature, so let’s at least try to put some evidence behind this question. That's what motivated us to look at it.

So is this the only study ever on this? Or the largest? What makes it unique?

The only study that I could find in the literature to look at this was one that was published back in 1991. It was actually a study focused on breast size, but they just reported some results looking at whether or not women wore a bra, so it’s a simple yes or no question, and they found nothing. No association there. But that was the only paper, so in many senses I'd say that ours is really the first study to do an in-depth analysis of bra-wearing and breast-cancer risk in the scientific literature.

The gold standard for studies is a randomized controlled trial — but I guess it would be pretty hard to find women willing to be assigned to wear bras or not...Your study is what's called a "case-control" trial — how would you characterize the quality level of the data?

Right, this is not a randomized trial, this is what we call an observational study, where we recruited women who had recently been diagnosed with breast cancer, and we also recruited a control group of women who had never been diagnosed with breast cancer. We asked them a series of questions about a variety of different things.

In general, the results from these types of studies are consistent with subsequent randomized trials, and it's usually studies of this type that might motivate a randomized trial. One recent example is the Women's Health Initiative and the finding of menopausal hormones being related to increased risk of breast cancer. That same increase in risk was seen in many case-control studies prior to the development of that randomized trial. So we can't necessarily draw causation — that there's a causal relationship between things in an observational study — but it can certainly give us important evidence as to whether or not a more definitive study is warranted.

And in this case, it looks like maybe it’s not warranted.

Yes, there really was no evidence [of a link], and we did a pretty detailed look. We looked at the age that women started wearing bras; the number of hours per day women wore bras; whether or not they wore one with an underwire.

The one limitation of the study is that we had very few women who never wore a bra. But we did have quite a bit of range — about 30% of women wore a bra for less than 10 hours a day, 25 percent wore a bra more than 16 hours a day. So there was quite a bit of range for the length of exposure, if you add that up over women’s lifetimes. Not seeing any effect with that fairly large difference in the number of hours a day would suggest there might not be that much going on here.

Does it make a difference that it was all post-menopausal women? Or does that not matter because it captures their earlier life too?

We got lifetime history. We didn’t do this in pre-menopausal women because the original study was focused on post-menopausal women. But you might also expect that post-menopausal women would be the group in which you’d expect to see the greatest effect because they have the longest number of lifetime hours they’ve worn a bra. And we also know breast cancer is much more common in older women than in younger women, so that would be the first logical group to look at.

Does the biological mechanism that believers in the link propose — constraining the flow of lymphatic fluid around the breast — make any sense?

Not to me. I haven't seen good evidence — there are no animal models I’m aware of that show that kind of blockage could increase breast cancer risk. The hypothesis relates to the way our lymph nodes kind of drain waste material, so because we’re exposed to different chemicals in the environment, or through food or whatever, and that lack of filtering of the waste material could somehow accumulate and lead to cancer. You’re talking about multiple things that would have to happen that are fairly theoretical. So there really is no solid scientific basis for that theory, in my view.

So how do you account for the fact that a theory like this takes such wide hold without any factual underpinning?

I think breast cancer is a challenge in many ways. It's the most common cancer in women, not only in our country but worldwide, and unlike a cancer like lung cancer, where if you eliminate smoking you can eliminate the vast majority of lung cancer, we don’t have the same thing with breast cancer. Almost all the risk factors that have been identified are very modest, and most of them, unfortunately, are not that modifiable.

The strongest risk factors for breast cancer are age — the older you are, the greater your risk — and having a family history of breast cancer. And those are two things that women cannot control. The other risk factors for breast cancer that are very consistent are related to reproductive factors like whether or not you have a child or whether you have a child at a younger age — and we’re certainly not going to promote teen pregnancy as a way to modify breast cancer risk.

So there just are not a lot of things that women can take control of in their lives to reduce risk, and I think that leaves the door open to theories like this: Saying that if you stop wearing bras you could reduce your risk of breast cancer is something women could potentially take hold of and take action on and do something about. Whereas most of the other risk factors, they can’t. And so I think it just creates an environment where things like this maybe gain more traction.

So what would be your take-home message from this negative finding?

Obviously, women should not be concerned about wearing a bra with respect to their risk of breast cancer, at least based on the results of this study. That's the main one. And just to be aware that breast cancer continues to be a major issue in our country and to talk to your doctor about what you can do, the availability of screening and whether that's the right choice for you. What are the things women can do to take control of their risk?

A frivolous last question: What about antiperspirants? I think of that theory as being in the same category as the bra theory...

Yes, that is actually something we also asked a series of questions about in the study. We have not published the results mostly because there's not a lot going on there either, and it has not been a high priority for us to do. There was some theory in the past that it was more the antiperspirants rather than the deodorants, because some of the chemicals in antiperspirants may be related to risk, but I have not read anything about that in recent years. I think that was something that kind of came and went more than a decade ago as something of concern. But again, there are very few papers on that topic and as far as I know, all of them are null.

Readers, were you worried? Are you still? 

Further reading:
Breast cancer risk factors
No, bras do not cause breast cancer (on Kevin MD)

Carey Goldberg Twitter Editor, CommonHealth
Carey Goldberg is the editor of WBUR's CommonHealth blog.

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