Does Wearing a Bra Increase Breast Cancer Risk?

Some people may be reluctant to wear bras because they worry that it could increase their risk of breast cancer. But there’s no evidence that wearing a bra affects your chances of developing breast cancer, even if you wear an underwire bra, wear it for most of the day, or even wear it overnight.

There hasn’t been much research into the link between bras and breast cancer because experts have always doubted that such a connection exists. But the little evidence that does exist shows that bras don’t cause breast cancer.

A 2014 study included 1,513 women between the ages of 55 and 74. Of these women, 1,044 of them were diagnosed with cancer between 2000 and 2004, while the rest did not have cancer. The researchers studied whether women with and without breast cancer had different bra-wearing habits. They found that no aspects of wearing a bra were linked to breast cancer risk. This included cup size, how recently they wore bras, average number of hours per day worn, wearing a bra with an underwire, or age when they started regularly wearing a bra.

The only other substantial research on the topic is a 1991 study that used similar methods. This study found that premenopausal women who don’t wear bras are half as likely to develop breast cancer than those who do wear bras. But the data aren’t strong enough to be confident in this result, so the link could be a chance finding. And this relationship could potentially be explained by cup size. Breast size is linked to body weight, so women with larger breasts are more likely to have either overweight or obesity, which are risk factors for breast cancer. They’re also more likely to wear a bra because it can help them with back pain from having heavy breasts. So, it may look like wearing a bra increases breast cancer risk, when really it’s having overweight or obesity that does.

The myth took off in 1995, due to a book called Dressed to Kill. The authors, husband and wife Sydney Ross Singer and Soma Grismaijer, claimed that breast cancer is more common in developed countries because most women living in them wear bras, whereas women in lower-income countries are less likely to wear bras.

They argued that compression from bras blocks the lymphatic system, sometimes called the body’s drainage system. The lymphatic system controls the flow of a liquid called lymph throughout the body, helps fight disease, and gets rid of waste. Their idea was that bras could block off the lymphatic system, which would stop toxins from exiting the body, trap them in the breasts, and cause breast cancer.

There is no evidence to support this argument. There are other, evidence-backed ways to explain the gap in breast cancer rates between lower- and higher-income parts of the world. In lower-income areas, breast cancer is less likely to be diagnosed because women have little access to medical care or to routine breast cancer screening. Differences in lifestyle, childbearing practices, diet, exercise, and other factors that affect breast cancer risk also help explain the gap.