Meta-analysis of 36 Chinese studies shows abortion increases breast cancer risk by 44%
December 2, 2013 (NRLC) - A new systematic review and meta-analysis of abortion and breast cancer (ABC link) in China, published last week in the prestigious, peer-reviewed international cancer journal, “Cancer Causes and Control,” showed that the overall risk of developing breast cancer among women who had at least one induced abortion was significantly increased by 44%. In this meta-analysis (a study of studies in which results from many studies are pooled), Dr. Yubei Huang et al. combined all 36 studies that have been published through 2012 on the ABC link in China.
These results, said the authors, “were consistent with a previously published systematic review.” This is a reference to the 1996 review and meta-analysis that I compiled with colleagues from Penn State Medical Center, and published in the British Medical Association’s epidemiology journal. Our study reported an overall significant 30% increased risk of breast cancer in worldwide studies.
Noteworthy is that the Huang study follows right on the heels of two new studies this year from India and Bangla Desh, studies which reported breast cancer risk increases of unprecedented magnitude: over 600% and over 2,000%, respectively, among women who had any induced abortions.
The new Chinese meta-analysis is a real game changer. Not only does it validate the earlier findings from 1996, its findings are even stronger, for several reasons:
1. The link is a slightly stronger one, i.e., 44% v. 30% risk increase with abortion;
2. It shows what is called a “dose effect”, i.e., two abortions increase the risk more than one abortion (76% risk increase with two or more abortions), and three abortions increase the risk even more (89% risk increase with three or more abortions). Risk factors that show such a dose effect have more credibility. Although previous studies of the ABC link were a bit more heterogeneous and the dose effect less clear, it has been shown that the risk increase is greater the longer the pregnancy continues before abortion. Hence, an 18-week abortion increases the risk more than a 12-week abortion, and a 12-week abortion increases the risk more than an 8-week abortion.
3. In their new meta-analysis Huang et al. put to rest the main argument used to discredit the ABC link, variously called the “response bias” or “recall bias” or “reporting bias” argument. The argument goes like this. Due to social stigma that is attached to having an induced abortion, healthy women are more likely to deny prior abortions in their medical history study questionnaire than are women who’ve developed breast cancer. Hence, the argument goes, it would erroneously appear that abortion is more frequent among women who’ve had an abortion.
Huang et al. dispatch of this canard. They explain, “The lack of a social stigma associated with induced abortion in China may limit the amount of underreporting and present a more accurate picture of this (abortion-breast cancer) association.” (This invokes an argument—the absence of social stigma– used by authors in an earlier Chinese study that did not find an ABC link.)
4. Huang et al. then proceed to explain why two earlier high-profile studies in Shanghai (including the one noted above) did not find the link. They do so essentially by citing and pursuing the argument I articulated in the “British Journal of Cancer” in 2004, and more importantly, proving the point by performing a “meta-regression” of all the Chinese data.
In my 2004 published letter, I explained that the Shanghai population was unsuitable for studying the ABC link in the usual manner, because the prevalence of induced abortion was too high in the general population.
In essence, the value of epidemiology is to identify exposures—like abortion—which may increase the risk of a given disease—like breast cancer—by comparing those exposed to the typical, unexposed population.
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But when the prevalence of the exposure becomes the rule rather than the exception—as in the Shanghai studies, where the majority of women had had at least one abortion—the unexposed women are not typical.
Instead they are women who have had no or fewer children and/or started having children at a later age, all of which put them at higher breast cancer risk.
Hence, comparing women who’ve had an abortion to women who are at elevated risk for other reasons makes the risk due to abortion tend to disappear. Huang et al.’s meta-regression analysis showed a clear tendency for the risk due to abortion to decline as the prevalence of abortion among the healthy population increases, among all the studies in China.
As noted above the Huang study follows two new studies from India and Bangla Desh which reported breast cancer risk increases of over 600% and over 2,000%, respectively, among women who had any induced abortions.
As I have shown in previous stories for NRL News and NRL News Today, objective research like this has been relentlessly targeted by the “mainstream” abortion advocates entrenched in universities, medical societies, medical journals, breast cancer charities, and especially, government agencies such as the National Cancer Institute (NCI).
This assault culminated in a 2003 international phony “workshop” by the NCI, which officially declared the ABC link non-existent. Since 2003, armed with this new official “truth,” NARAL and their ilk have unapologetically and publicly attacked pro-life pregnancy resource centers for “lying” to women by telling them about the ABC link. In places like Maryland and San Francisco and Austin and New York City, they even went so far as to enact laws to muzzle these women helping centers. Thankfully, most courts have struck down such laws as violations of free speech rights–so far.
It is really frightening when you start doing the math on the impact of abortion on a population of over a billion women—in India and China alone: Just a 2% lifetime risk of breast cancer due to abortion—a very conservative estimate—means upwards of 10 million women getting breast cancer, and millions dying from it. Hopefully, the day is near when the official purveyors of public health information—like the NCI—will no longer be able to deny the ABC link. The new Chinese meta-analysis should hasten that day considerably.
Reprinted with permission from NRLC