Last Updated: Monday, November 26, 2007 | 4:58 PM ET
CBC News

Urban-dwelling women are more likely to have dense breasts, suggests new research presented Monday.

Previous studies have found that having very dense breast tissue, which means the breasts have more glandular tissue than fat, means a woman has four times the risk of developing breast cancer.

Women who live in downtown London are about 1½ times more likely to have greater breast densities than those in rural areas, researchers found.

The findings were presented at the annual meeting of the Radiological Society of North America in Chicago, which runs from Nov. 25 to 30.

Researchers at the London Breast Institute at the Princess Grace Hospital reviewed digital mammograms of 617 women aged 29 to 87 who lived in urban, surburban and rural areas of London, England. They studied 225 mammograms from rural residents, 135 from surburban dwellers and 257 from urbanites.

One hundred and sixty-one of the mammograms were found to be "entirely fatty," meaning there was no glandular tissue; 187 had scattered fibroglandular densities, a mixture of fat and glandular areas; 136 were considered "heterogeneously dense;" and 133 were "extremely" dense.

Thirty-one per cent of women from rural areas had entirely fatty breasts, compared to 26 per cent of suburban women and 22 per cent of urban women.

Women who lived in downtown London had "significantly" denser breasts than those who lived outside the city, the researchers say. The relative risk of greater breast density if a woman lived in an urban area 1.54 and 1.14 for women in surburban areas, compared to those in rural areas.

The risk of density was twice as high in women aged 45 to 54, the study found.

"Women living in cities need to pay more attention to having regular breast screening," said one of the researchers, Nicholas Perry, the director of the London Breast Institute.

"Currently, women who live in urban areas are known to have lower attendance for breast screening programs than women in outlying areas," Perry said in a news release issued Monday.

Perry suggested women with dense breasts undergo testing via digital mammography, which he feels is better at detecting cancers.

He also warned that more research is needed regarding the causes of breast density before any definitive conclusions can be made.