Earlier this week I read the online article "Breastfeeding reduces ovarian cancer risk by 91%". I had breastfeed my daughter so I was interested in more details about the study. So I searched for the actual breastfeeding study in the American Journal of Clinical Nutrition to learn more. Although I could not read the entire article I could read the abstract.
Just reading the title Ovarian Cancer risk is reduced by prolonged lactation :a case controlled study in southern china hinted that the study might hold some surprises. I had wrongly assumed the study was done in Australia since the article I read reported the researchers were from Australia. There was no mention in the article that the study subjects were from Guangzhou, Gunagdong Province in China. Between August 2006 and July 2008 women were given a questionnaire and asked to recall how many months they breastfeed (lactated ) and how many children they breastfeed. The questionnaires were given to 493 women with ovarian cancer and 473 women in the control arm. The mean age of the women was 59.
The Australian researchers found an inverse relationship between breastfeeding and ovarian cancer risk and an inverse relationship between the number of children breastfeed and ovarian cancer risk. In other words the longer you breast feed the lower your ovarian cancer risk and the more children you breastfeed the lower your ovarian cancer risk. The researchers concluded "Prolonged lactation is associated with a lower risk of in parous Chinese women."( Parous women are child bearing women.) So the study's conclusion related to Chinese women, not Autralian, American or European women.
This study was a retrospective study. In these type of studies researchers ask participants to recall if they did or used something ( breastfeed, exercise, drink coffee, use a drug) to determine if it was a factor in developing a disease or condition later in life. If you asked me today in 2013 how long I breastfeed my daughter back in 1982 I would not be able to give you an exact answer. Was it 6 months? 9 months? I don't think it was more than 12 months but I am not sure. So in this type of study patient recall can impact the results.
This study is interesting. But if we repeat the study in the US would we get the same results? The original article I read did not mention other studies to support the results of the Australian study but did note the benefit of breastfeeding to lower their risk of ovarian cancer.
Well, I did some research and back in 2007 the study "Breastfeeding and risk of ovarian cancer in two prospective cohorts."was published. The results are part of the Nurses Health Study and was a prospective study. A prospective study starts out with a healthy population with certain characteristics ( like having breastfeed) and the subjects are followed over time to see if a particular disease develops. This study concluded that there was no significant reduction in risk of ovarian cancer in women who ever breastfeed or never breastfeed. But women who breastfeed 18 months or longer did show a significant reduction in risk for epithelial ovarian cancer.The average length of breastfeeding in this study was 9 months.
The conclusion of both studies is about increased risk of developing the disease. This Women's Cancer Network page does a nice job of explaining ovarian cancer risk. The average woman's risk of developing ovarian cancer is 1 in 70.
I enjoy reading articles about cancer research studies and the related journal abstracts but sometimes find it frustrating that crucial details about the studies are often missing from media accounts.
Every Day is a Blessing !