Urban women face higher breast cancer rates.

Dey, S, AS Soliman, A Hablas, IA Seifeldein, K Ismail, M Ramadan, H El-Hamzawy, ML Wilson, M Banerjee, P Boffetta, J Harford and SD Merajver. 2010. Urban-rural differences in breast cancer incidence in Egypt (1999-2006). The Breast http://dx.doi.org/10.1016/j.breast.2010.04.005.

Another study in yet another country finds that women living in cities have higher rates of breast cancer when compared to women living in the country.

The results from Egypt parallel previous reports of urban-rural differences in breast cancer incidence from China and India. In those countries, urban living increased breast cancer rates by the same margins of three to four  times when compared to rural environments. Collectively, these studies point to environmental factors that may be significantly contributing to breast cancer incidences in developing countries.

Few genetic differences between women living in urban and rural Egypt allowed researchers to study the role of environmental factors. The higher rates were observed every year for the eight year study period and were significantly different even when differences in age were accounted for.

The women in the study live in the Gharbiah region north of Cairo. A disase registry provided general lifestyle and health-related information about the women who were diagnosed with breast cancer between 1999 and 2006.

In both residence groups, breast cancer rates increased as women aged, up to ages 45-55. After women reached age 55, breast cancer rates decreased, although they never reached the low levels observed in the youngest age groups.

Breast cancer rates increased slightly in women living in rural environments during the 8 year study. These increases could be due to the gradual acceptance of urban lifestyles in women that live in rural areas, including different reproductive habits and exposure to similar environmental contaminants due to economic development.

Better detection rates were not responsible for the observed differences. Egypt has 100 percent health care coverage, and excellent physicians are available in rural settings. Additionally, the rural areas examined in this study were no more than 50 kilometers away from large hospitals in major cities that were well connected with inexpensive public transportation. Finally, the tumors observed in the women were of comparable disease stages, suggesting that there were similar levels of cancer progression in these two groups.

At this time, researchers can only speculate about the differences. One factor may be that urban women have fewer children and are less likely to breastfeed. Previous studies have shown that Egyptian women that breastfeed more have lower internal levels of pesticides. Other studies indicate that xenoestrogens and carcinogens are more abundant in urban areas, specifically high levels of inorganic pollutants and heavy metals that have contaminated the urban Nile River. Epidemiological studies are needed to determine whether any of these factors can be more definitively linked to increased breast cancer incidence.