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Asian women who immigrate to the United States may have a higher risk of breast cancer than those born here, new preliminary research has found, an apparent shift from historical norms of U.S. women having higher breast cancer rates compared to the rest of the world.

The new study, published online last week in the medical journal Preventing Chronic Disease, found that Asian women who had immigrated to the United States and spent more than half their lives in the U.S.were on average three times as likely to have breast cancer compared to Asian-American women who were born in the U.S. Those who immigrated and spent less than 50 percent of their lives in the U.S. were on average 2.46 times more likely to have breast cancer.

According to study co-author Brittany Morey, a postdoctoral researcher at the University of California, Riverside School of Public Policy, that information was surprising because it was the opposite finding of past studies.

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Earlier research, which examined data from the ‘70s to the early 2000s,has found that women in the U.S. generally had higher rates of breast cancer than demographically comparable women abroad.

The shift could be caused by the “effects of globalization and economic development,” researchers hypothesized, including increased access to breast cancer screenings, later childbirth, decreased breastfeeding and sedentary lifestyles, which are all associated with a higher risk of breast cancer.

The study, which takes into account age and country of origin, examined a data set of women in the San Francisco Bay Area recruited between March 2013 and October 2014 that yielded a sample of 570.

Further research is needed to corroborate the study’s findings especially outside of the Bay Area, Morey told NBC News.

"If true ... we need to focus on treating breast cancer in this population, and there needs to be a focus on services for foreign-born Asian-American women," Morey said, citing language and cultural needs, including culturally sensitive ways to talk about cancer.

“Interventions are needed to increase breast cancer screening among both immigrant and U.S.-born Asian-American women to prevent breast cancer from progressing,” the study said.

Recent research has found that breast cancer rates have increased for Asian-American women, even as they remain stable in the U.S. overall.

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