Bras have no connection to breast cancer, according to a new study from the University of Washington.

A popular belief held that post-menopausal women increase their risk of breast cancer by wearing the undergarments. The idea started as an effort to explain why women in developed countries have higher rates of breast cancer than adult females in the developing world.

Dressed To Kill: The Link Between Breast Cancer and Bras by Sydney Ross Singer and Soma Grismaijer presented evidence bra-wearing could encourage the development of breast cancers.

More than 1,500 women were studied by researchers investigating a possible link. Subjects included 590 women diagnosed with invasive lobular carcinoma (ILC), as well as 454 suffering from  invasive ductal carcinoma (IDC). All subjects were post-menopausal, and each initial diagnosis was made between the years 2000 and 2004. The remaining 469 subjects were free of the diseases.

The women were asked questions regarding their history of bra-wearing. These included the age at which they began wearing the garments, whether or not they wore bras with underwires. The amount of time the subjects wore the garments, and how usage changed over time, was also collected.

No evidence was found in the study for the idea that wearing bra increases risks of breast cancer. Researchers carefully studied the data, attempting to find any connection between clithing habits of women and the two forms of cancer. No correlations could be found between either ILC or IDC and wearing of the undergarments.

"There has been some suggestion in the lay media that bra wearing may be a risk factor for breast cancer... Given very limited biological evidence supporting such a link between bra wearing and breast cancer risk, our results were not surprising. We knew that the biological plausibility of a link between bras and breast cancer was really weak," Lu Chen, a doctoral student at the University of Washington School of Public Health, said.

Sydney Ross Singer questioned why researchers only studied post menopausal women in the study, suggesting the team may have a "pro-bra bias." Researchers responded that all cancers, including the pair studied, become more common with age. In addition, they stated, most older women have worn bras longer than younger females, making any effect more apparent.

The American Cancer Society conducted a survey in 2002 showing six percent of women believe underwire bras can cause breast cancer. Nearly one-third of respondents - 31 percent - reported they did not know if there might be a connection.

Investigation of how wearing brassieres can affect the development of breast cancer was detailed in the journal Cancer Epidemiology, Biomarkers & Prevention.

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