MONDAY, Nov. 26, 2007 (HealthDay News) -- Women who live in urban areas appear to have more dense breast tissue than their suburban or rural counterparts, new research suggests.
The finding is potentially important because women with more dense breasts have a higher risk of breast cancer.
The study, which compared women living and working in London to those living outside the city, found that city-dwelling women were more likely than their rural peers to have dense breasts.
"Our study suggests that the closer to urban and high population densities that a woman resides, and in particular works, the greater likelihood there is that she will have denser breasts," said study author Dr. Nicholas Perry, director of the London Breast Institute at the Princess Grace Hospital.
"For every 1 percent increase in breast density, there is said to be a 2 percent increase in the relative risk of developing breast cancer," he added.
Perry was to present the findings Monday at the Radiological Society of North America's annual meeting, in Chicago.
Each year, nearly 180,000 American women are diagnosed with invasive breast cancer, and about 40,500 die from the disease, according to the American Cancer Society (ACS). Over a lifetime, about one in eight women will develop breast cancer.
Known risk factors include a family history of the disease, getting your first period before the age of 12, beginning menopause after age 55, not having children or having your first child after 30, being overweight, drinking more than one alcoholic drink a day, and living a sedentary lifestyle, according to the ACS.
The new study included digital mammograms from 972 women, between 29 and 87 years old, living or working in rural, suburban and urban areas. Two hundred and twenty-five women were from rural areas, 135 lived in the suburbs, and 257 women either lived or worked in an urban area.
Breast density isn't an indicator of breast size, noted Dr. Julia Smith, director of the New York University Cancer Institute's Breast Cancer Screening and Prevention Program. Instead, breast density indicates more glandular breast tissue and ducts rather than fatty tissue. That means more area for breast cancer to develop and hide, she explained.
Overall, 26 percent of the women in the study had breasts that were classified as fatty, while the remaining women had density findings ranging from scattered to extremely dense. Thirty-one percent of the rural residents had breasts classified as fatty, while 26 percent of suburban women and just 22 percent of urban women did.
Perry and his colleagues found that women who lived and worked in a city were more likely to have dense breasts than either their rural or suburban counterparts. Urban women had a 54 percent greater chance of having dense breasts than women living in rural areas, and suburban women had a 14 percent higher risk of dense breasts than rural women.
"This is an interesting finding," Smith said. "But, we need to tease out the confounding factors. Are these population issues or does being in an urban environment increase risk?"
For example, she said, urban women may have better diets and may exercise more, both of which can contribute to denser breast tissue, Smith said.
Perry also said there are many lifestyle factors that need to be considered, and he hopes that now that he and his colleagues have drawn attention to the issue, more studies will be done to uncover the cause of this disparity.
One concern that Perry has is that past studies have found that urban women may be less likely to undergo screening for breast cancer, and this study suggests that it may be even more important for these women to get mammograms as recommended.
"All women should be given the opportunity to participate in breast screening programs, if eligible, but perhaps women in the city need to be extra vigilant in this regard and not miss out," Perry said.
More information
To learn more about breast cancer prevention, visit BreastCancer.org.
