I saw this meme on FaceBook the other day. Wow, those figures are pretty convincing, aren't they? Or are they? I don't think I would've even noticed had I not just read an article - from a reputable source - that presented very different numbers.
I think I can safely say for all of us that breast cancer is pretty much every woman's worst nightmare. And while it is true, that some studies have found a correlation between reduced risk and duration of total nursing time as well as number of children breastfed, it is not conclusive. Despite everything - the money poured into awareness campaigns and research, "not much research has looked at links between breastfeeding and a lower risk of particular types of breast cancer in particular women."
That also doesn't mean it's an absolute that you won't get breast cancer if you breastfed, long-term or otherwise. I still remember a college professor of mine detecting her cancer literally while she was nursing her baby (who I believe was two at the time). In fact, one of the women commenting on the thread where this was originally shared said she'd been diagnosed with it while nursing her fourth child.
One thing that bugs me a lot about this meme is the complete lack of sources. Where is this information from? The first rule of thumb we learn in any basic composition class is "Always site your sources." When pressed for further data or information, the moderator of the page where this was shared kind of shrugged it off and figured the American Cancer Society would have more information. While I don't think she was the creator of this graphic, she was passing along incomplete information and didn't even realize it.
In fact, the American Cancer Society has something very different to say:
"For every 12 months of breastfeeding (either with only 1 child, or as the total period of a time for several children), the risk of breast cancer decreased by 4.3%, compared to women who did not breastfeed. Risk decreased by 3.4% for each child breastfed, compared to women who did not breastfeed. This lower risk did not differ by women's age, race, numbers of births, age at birth of first child, family history, or country of residence." - American Cancer Society Expert Voices (click here for full article text)Something this meme doesn't address are the types of breast cancer impacted, which can be important - because some studies show that breastfeeding can offer protection from certain types of cancer more than others. As the article suggests, the studies are inconclusive, but so far seem to show more risk reduction for hormone receptor-negative cancers, which are more aggressive. While there is some evidence that breastfeeding can impact rates of hormone receptor-positive cancers, (which are the most common and are 'fueled' by estrogen), in my own reading I found it difficult to determine statistically how much protection was offered, and was concerned that advocacy groups and the general public are simply lumping the two together as one.
That's not to say that there isn't some very promising, important data to consider, like these studies:
• Delaying childbirth may reduce the risk of an aggressive form of breast cancer - from December 2012. Studies have shown that delaying the age of your first birth by at least 15 years after your first menstrual period could reduce the risk of rare but aggressive triple-negative breast cancer, by as much as 60 percent. While uncommon, it does not depend on estrogen to feed it, and is therefore unresponsive to conventional drugs like Tamoxifen. It accounts for roughly 10-20 percent of breast cancers.
• Breastfeeding can reduce the risk of certain types of breast cancers. Recent studies have shown that breastfeeding can reduce the risk for estrogen receptor-negative and progesterone receptor-negative cancers, in women who had three or more children and did breastfeed. Risk was elevated in multiparous women who did not breastfeed. This type of cancer often strikes younger women and has a poor outlook. (The study also showed that in women who never had children, their risk decreased by 40% for hormone receptor-negative cancers, but went up by the same amount for hormone receptor-positive cancer.)
Race can also be a factor in hormone receptor-negative cancers: African-American women who had four or more children but never breastfed are 68% more likely to get this type of cancer, compared to women who had only one child but did breastfeed. Studies showed that with each child breastfed, the risk declined. The study also showed that among African-American women who had given birth four or more times, there was slight protection against hormone receptor-positive cancers, regardless of whether they breastfed or not. The same was found for white women.
"The higher incidence of ER-/PR- breast cancer in African American women may be explained in part by their higher parity and lower prevalence of breastfeeding relative to white women." - Julie Palmer, ScD, MPH, senior epidemiologist at the Slone Epidemiology Center and professor of epidemiology at Boston University School of Public Health
• A Canadian study showed promise for those with a family history of breast cancer - specifically those with the BRCA1 gene (which is more often hormone receptor-negative), stating that breastfeeding for a year could reduce their chance of cancer by 32%, and with "each year of breastfeeding, it reduced their risk by 19%. "With two or more years of breastfeeding, that risk was nearly cut in half. Researchers "calculated that just five women with the BRCA1 gene needed to breastfeed for a year to prevent one developing cancer." It's important to note, however, that these benefits were not observed with women carrying the BRCA2 gene (which is more frequently hormone receptor-positive).
An earlier US study found, however, that among women with a family history of breast cancer, there was a 59% reduction in risk of getting premenopausal breast cancer, but did not specify which type. (Most likely it is hormone receptor-negative.) The study also noted the duration of breastfeeding did not seem to make a significant impact, and noted "the reduction in risk was similar whether women breastfed for a lifetime total of three months or more than three years." Nor was there a difference noted among women with no family history.
Personally, I think it's important to look at several things when presented with statistics: first, what is their source? Is the study old, and have newer, more accurate studies come out since then? What population did they study? What factors did they include, or exclude?
For instance, an interesting study was conducted by a Chinese researcher at Yale University, which was entirely comprised of Chinese women, mainly because he claimed they have substantially longer breastfeeding rates than the United States. His research (which was published in 2001) looked at three studies conducted in the 1980's, not long after China adopted their infamous one-child policy. Given what we now know about cancer rates and multiparous women and their breastfeeding habits, it is a wonder he could find any woman who had managed to give birth more than once to even do the study. (The one-child policy applies to roughly a third of the population, but the overall parity rate of Chinese women as of 2013 is about 1.5 children, suggesting it has become a cultural standard to have lower birth rates overall.)
While he found a "50 percent reduction in breast cancer risk among those women who breastfed for more than 24 months per child, compared to women who breastfed their children for less than 12 months," it's interesting to note that according to this article, China's breastfeeding rates have "plummeted since the 1970's" when infant formula was introduced. In the 1980's, when these studies were conducted, breastfeeding rates in China were at their lowest.
While this might be good news for Chinese women, it is hard to tell if it correlates to Western women for a number of reasons. Dietary and lifestyle differences can also impact cancer rates, and vary widely between East and West populations. And while this study was published in 2001, as of now roughly 58% of Chinese women exclusively breastfeed their newborns, whereas it drops sharply to around 14% by five months, making it on par with the United States. (And by month six, it nosedives to an alarming 2%.) As of 2013, it was declared that China's breastfeeding rates were "among the world's lowest."
The researcher claimed, "In Chinese society, it is socially acceptable to breastfeed for a long time." Could it really have changed that much in a little more than a decade?
Either way, we need to be careful not only in how we share the data, but how we interpret it. When reading these kinds of statistics, pay close attention to what sources, if any, are listed. Likewise, realize that there could be flaws, unanswered questions or stipulations in those numbers that are not reflected in a meme that merely spews out numbers without proof, leaving the reader with a false sense of confidence and security about a very serious topic. It's important to not take the data as a personal attack as long as it's shared appropriately or dismiss the benefits of breastfeeding for both mom and baby. Likewise, studies should be shared without judgment or hostility. Whether in sharing or interpreting this data, it's so important to get the facts straight and understand the caveats that could seriously impact our understanding of our own level of risk.
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Sources:
The Chinese government really, really wants babies to breastfeed - Quartz.com (a good piece that is particularly damning of the heavy influence of infant formula in the Chinese market)
Multiple childbirth linked to increased risk of rare, aggressive 'triple-negative' breast cancer - ScienceDaily
Lactation linked to reduced estrogen receptor-negative, triple-negative breast cancer risk - ScienceDaily
