On Monday we previewed Dr. Funmi Olopade’s public lecture at the Harold Washington Public Library in Chicago titled “Nature, Nurture and Breast Cancer.” For that post, I talked about some recent work from Olopade’s research group that compared the types of breast tumors found in West African women with the tumors seen most often in black and white American women. That research indicated that there likely is a genetic difference between women of African origin and Caucasian, North American women that leads to fewer breast cancer cases but a higher rate of aggressive, harder-to-treat tumors in black women here and abroad. But the patients from Senegal and Nigeria which Olopade’s group studied also showed different proportions of tumors when compared to African-American women, suggesting a strong role for environmental factors in causing breast cancer as well.
In her library appearance Tuesday evening with NBC reporter Dr. Mary Ann Malloy, Olopade expanded upon those mysterious “environmental factors” that likely contribute to the higher breast cancer numbers in North America. To a rapt audience, Olopade listed off the most well-known and common risk factors for breast cancer: age, family history and “the most important risk factor,” being a woman.
(Chicago Public Radio’s Chicago Amplified is supposed to post audio from Tuesday night’s event, but it’s not up yet. I’ll add a link when it’s available.)
But even to a crowd that, judging from their questions, was very well informed about breast cancer medicine and science, Olopade inspired gasps of surprise by rattling off some less-publicized environmental factors: breastfeeding, age at childbirth, even height. Many of these factors, in combination with more mundane things like lack of moderation in diet, exercise and alcohol intake, are behaviors more commonly seen in rich countries where women have achieved a more equal status in their work and private lives.
“I think what we’re still struggling with is, as we get more affluent and as people live the good life, then you see the rising incidence of breast cancer,” Olopade said. “We want people to have the good life, but what is it about the good life that is predisposing us to breast cancer?”
Here are links to a couple of the studies which informed Olopade’s comments Tuesday night:
Breastfeeding: In her comments, Olopade mentioned that her mother had six children and may have spent as much as 120 months of her life breastfeeding her children. Today, she is 90 years old and “doing very well,” Olopade said. That’s anecdotal evidence, obviously, but a survey study conducted by Olopade’s group in Nigeria found that breast cancer risk is reduced by 7% for every 12 months of breastfeeding. An older study of more than 4500 American women found that women that breastfed for more than 25 months lowered their risk for breast cancer by a third compared to women that had nevert breastfed. And because there’s plenty of evidence that breastfeeding is beneficial for the child as well, it has a double benefit.
“The most protective factor that women have against breast cancer is breastfeeding,” Olopade said. “Not only does it help the mother, it helps the baby.”
Height: Another Olopade study conducted in Nigeria looked at the potential associations between physical characteristics like weight and height with the incidence of breast cancer. Unusually, obesity was not the villain of this study – obese women were not found to have a significantly higher chance of contracting breast cancer. But taller women were at more risk, which Olopade suggested may indicate a link between growth hormones and the development of breast tumors. A recent review that looks at a whole slew of risk factors for breast cancer doesn’t offer much in the way of explanation about why height may predispose women to breast cancer, suggesting that this connection remains a clinical mystery.
Alcohol: No Olopade Nigeria study on this factor, but a recent review article using the very large data set of the Women’s Health Study (with more than 38,000 subjects enrolled) does a good job of summarizing the contribution of alcohol to breast cancer. They describe the effect as “modest” – consuming more than 30 grams a day of alcohol (about two drinks) each day raised the chance of developing breast cancer by 32%, what the authors term a “modest” effect. Interestingly, the increased risk seems to be specific to tumors that express hormone receptors, the easiest type of breast cancer to treat.
If all of these statistics seem overwhelming, Olopade said her best piece of advice to women was to use common sense and avoid the excesses sometimes associated with the American lifestyle.
“I think we have to come back and think about doing things in moderation,” Olopade said. “Be sensible with what you do, and make sure you take all the food groups, use antioxidants, exercise, sleep well, reduce stress in your life, and just be sensible.”