Health Editor’s Note: Let’s face it. Talking about having cancer is scary and unpleasant (too mild of a word). Having cancer is more than scary. We cannot avoid knowing as much as we can about cancer. To do so, may very well kill you or someone you know and love. Breast cancer in women ranks just below the number one cancer, lung cancer. Roughly 30% of newly diagnosed cancers in women will be from breast cancer, just behind the diagnosis of skin cancer, which as described in previous health articles on skin cancers, supplies huge numbers of cases per year.
As noted in my previous articles regarding breast cancer and testing, breast cancer is not just a cancer for women. Men get it too, although it is far more prevalent in women. Overall about 1 in 8 women will develop invasive breast cancer, men have a 1 in 1,000 risk. According to Breastcancer.org, after two decades of increasing breast cancer rates, breast cancer began decreasing in 2000 with the theory that hormone replacement therapy (HRT) was decreasing as there was a distinct connection between women who received HRT and an increase in breast cancer diagnoses. Treatment advances, earlier detection, breast cancer awareness are all saving more women who have breast cancer, even those with advanced stages of cancer. African-American women are most at risk for dying from breast cancer. White, Asian, Hispanic, and Native-American women have a lower risk for women under 45. Having a mother, sister, or daughter with breast cancer increases the risk of breast cancer, but that being said, less than 15% of women with breast cancer have a family member who has had it. So the other 85% occur in women with no family history and occur due to genetic mutations (where a cell divides and becomes something that it was not supposed to be).
So with 85% of breast cancers not being driven by genetics, there has to be other reasons and causes for the development of breast cancer. Since the fat cells in the body produce female hormones (and many other hormones as well), that can stimulate cancer growth if the tumor is sensitive to those hormones, there is a risk of feeding cancer cells what they need to grow. The risk of being overweight, with additional body fat deposits, most probably in come cases can lead to developing breast cancer. With the factor of being overweight, then we have to look at why the woman is overweight. Is it due to poor access to nutritious foods? If so, we can add socioeconomic causes to the mix. Growing older, which we are all in the process of doing, is another factor in developing breast cancer. Perhaps the most accessible tool in our bag to avoid breast cancer is to avoid being overweight by exercising (walking is great) and eating healthy will help you to loose excess body fat. Plus, think how much better you will feel…. Carol
By Michael Broder, PhD
Reviewed by Vrunda Desai, MD, Assistant Professor of Obstetrics, Gynecology, and Reproductive Sciences, Yale Medical School, New Haven, CT
Obesity is well established as a risk factor for breast cancer. A recent study found that for every 5 kilograms gained in body weight since early adulthood, the risk of postmenopausal breast cancer increased by 11% (among women not on hormone replacement therapy).1,2 Another study showed a differential impact of excess adiposity on breast cancer risk across racial and ethnic categories.1,3 Yet another study found that both body mass index (BMI) and adult weight gain significantly increased the risk of breast cancer in the overall study population, but the increase was greater among Native Hawaiians and Japanese Americans than among White, African American, and Latino women who had the same BMI.1,4
We know that the neighborhood environment has an impact on adiposity and obesity; and we know that obesity is a major modifiable risk factor for postmenopausal breast cancer. What has received less attention is the impact of obesogenic environmental factors on breast cancer risk. By obesogenic factors, we mean those social and manufactured attributes of a residential area that promote weight gain and obesity. Knowledge about the impact of obesogenic environmental factors on breast cancer risk could translate into new prevention measures. For example, we know that factors such as poverty, poor nutrition, and lack of recreational facilities promote weight gain. But there has been minimal data on any direct association between obesogenic environmental factors and breast cancer risk; no studies have determined whether obesogenic factors in the residential environment can account for the documented associations between body weight parameters and breast cancer risk.1 Moreover, studies examining these types of factors are difficult to conduct and to evaluate accurately, given underlying biases and the challenge of identifying a truly causal relationship.
While the neighborhood environment has an impact on obesity and obesity is a major risk factor for breast cancer, the impact of obesogenic environmental factors on breast cancer risk has not been well studied.
A new study assessed the association between specific obesogenic factors and breast cancer incidence in residential areas in a cohort of African Americans, Japanese Americans, Latinos, and Whites.
Lower neighborhood socioeconomic status was associated with lower breast cancer risk overall. More urban environments were associated with decreased breast cancer risk in Japanese Americans, and a lower level of mixed-land development was associated with higher breast cancer risk in Latinos.
To address these knowledge gaps, Conroy and colleagues assessed the association between breast cancer incidence and specific obesogenic factors in residential areas. The researchers sought to test the hypothesis that neighborhoods with lower socioeconomic status, more urban characteristics, more unhealthy foods, fewer recreational facilities, and fewer parks would be associated with an increased breast cancer risk.1
The study included 48,247 postmenopausal women enrolled in the Multiethnic Cohort Study (MEC), an observational cohort established in 1993 to study the role that diet and other lifestyle factors have on cancer risk.1,5-7 Participants included women from four racial or ethnic groups living in California: African Americans, Japanese Americans, Latinos, and Whites.1
The study analyzed 5 “neighborhood obesogenic factors”—composite factors known to drive weight gain and obesity—and their impact on breast cancer risk. These factors included neighborhood socioeconomic status, urban environment, mixed-land development, unhealthy food options, and parks. Neighborhood socioeconomic status was a composite of data for education, housing, employment, occupation, income, and poverty. The urban environmental factors included characteristics such as high population density and high traffic density; mixed-land development referred to as more recreational facilities and businesses per capita; unhealthy food outlets meant a high ratio of unhealthy to healthy restaurants; and parks denoted a high number of parks per capita.1
During the nearly 17 years of follow-up, 2341 women in the cohort were diagnosed with invasive breast cancer. Using Cox proportional hazards regression, the study assessed the association between the 4 neighborhood obesogenic factors and breast cancer risk, adjusting for prediagnostic BMI, weight gain since age 21, and established risk factors.
The most significant associations had to do with neighborhood socioeconomic status, urbanicity, and mixed-land development; but although these factors were independently associated with breast cancer risk, they were also differentially associated by race and ethnicity. In particular, lower neighborhood socioeconomic status was associated with lower breast cancer risk (Quintile 1 vs 5: hazard ratio (HR), 0.79; 95% confidence interval (CI), 0.66-0.95), an association that was more pronounced among Latinos (Quintile 1 vs 5: HR, 0.60; 95% CI, 0.43-0.85). In addition, more urban environments were associated with decreased breast cancer risk in Japanese Americans (Quintile 5 vs 1: HR, 0.49; 95% CI, 0.26-0.90). Moreover, a lower level of mixed-land development was associated with higher breast cancer risk in Latinos (Quintile 1 vs 5: HR, 1.46; 95% CI, 1.10-1.93).1
While Conroy and colleagues found a reduced breast cancer risk in women with lower neighborhood socioeconomic status, these women also had higher rates of morbidity and mortality.1
“It is important to note that women of lower socioeconomic status have lower survival after breast cancer diagnosis, and we believe that this is due to their being more likely to be diagnosed at [a] later stage, and less likely to receive guideline treatments,” said Scarlett Lin Gomez, PhD, MPH, Research Scientist at the Cancer Prevention Institute of California and a coauthor of the Conroy study.
Published: March 29, 2017
- Conroy SM, Clarke C, Yang J, et al. Contextual impact of neighborhood obesogenic factors on postmenopausal breast cancer: The Multiethnic Cohort. Cancer Epidemiol Biomarkers Prev. 2017 Jan 31. [Epub ahead of print]
- Keum N, Greenwood DC, Lee DH, et al. Adult weight gain and adiposity-related cancers: a dose-response meta-analysis of prospective observational studies. J Natl Cancer Inst. 2015;107:2.
- Bandera EV, Maskarinec G, Romieu I, et al. Racial and ethnic disparities in the impact of obesity on breast cancer risk and survival: a global perspective. Adv Nutr. 2015;6:803-819.
- White KK, Park SY, Kolonel LN, et al. Body size and breast cancer risk: the Multiethnic Cohort. Int J Cancer. 2012;131:E705-E716.
- University of Hawai’i Cancer Center. The Multiethnic Cohort Study.
- Kolonel LN, Henderson BE, Hankin JH, et al. A multiethnic cohort in Hawaii and Los Angeles: baseline characteristics. Am J Epidemiol. 2000;151:346-357.
- Stram DO, Hankin JH, Wilkens LR, et al. Calibration of the dietary questionnaire for a multiethnic cohort in Hawaii and Los Angeles. Am J Epidemiol. 2000;151:358-370.