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Establishing the Evidence PDF Print E-mail


The research we have on breast cancer risk factors is from studies completed in the last 3-5 years that have been rigorously reviewed and published in reputable journals. Our references are sources like the Canadian Cancer Society, the Canadian Breast Cancer Foundation, the National Cancer Institute of Canada and Cancer Care Ontario as well as several international sources.



There are varying levels of scientific evidence that link some risk factors to breast cancer more strongly than others. For instance, there is currently no evidence to support the claim that sleeping in a bra can cause breast cancer. Though our knowledge could change in the future as more research is done, we cannot consider sleeping in a bra to be a risk factor at this time. For other factors (such as being exposed to environmental chemicals like bisphenol A or parabens), current scientific evidence is either “preliminary” or “inconclusive”. That means that we don’t know if these substances do in fact increase the risk of breast cancer or how they might do so. In other cases the evidence is considered “suggestive” or “probable” and more studies have to be done to more clearly establish a linkage and a clear explanation for the study results. This is the case with tobacco smoke.


On the other hand, the three lifestyle factors (nutrition, physical activity and drinking alcohol) have been well-established in the link to breast cancer, through a number of rigorous studies. Interestingly, the evidence linking alcohol to increased risk for breast cancer is considered “convincing” – the very highest level of judgment from the scientific community.

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