Mayo Clinic Study Finds Scandinavian Women at Increased Risk for Breast Cancer and Irish Women at Decreased Risk.

ROCHESTER, Minn.--(BUSINESS WIRE)--July 16, 1999--

A new Mayo Clinic study has found that Scandinavian women are at increased risk of developing breast cancer compared with other Caucasian ethnic groups. The lowest risk was observed in Irish women.

"This is believed to be the first study of its kind to look at breast cancer frequency among various Caucasian ethnic groups," says Thomas Sellers, Ph.D., a Mayo Clinic epidemiologist and lead author of the study. "Previous studies have grouped all Caucasians together when studying breast cancer risk, but this study suggests that risks vary among Caucasians."

Researchers found the highest rates of breast cancer were observed among Norwegian and Swedish women (488 per 100,000 per year) and the lowest among Irish women (353 per 100,000 per year). This indicates that Scandinavian women are at 40 percent greater risk of developing breast cancer than Irish women, according to the researchers.

The study also found that a family history of breast cancer was associated with increased risk among English, Scottish, Welsh and Dutch; Germans; and other Europeans (Southern Europeans, Eastern Europeans, Central Europeans and Western Europeans); but not among Irish and Scandinavians.

"Family history of breast cancer is considered one of the most important risk factors for the disease," says Dr. Sellers. "This study suggests, however, that risk associated with family history may vary among ethnic groups."

The researchers call for caution, however, in taking action based upon a single study. "This study is the first of its kind," says Dr. Sellers. "There is more research to do. I'd also remind women that regardless of their ethnic background, every woman is at risk for breast cancer and should consult with her physician about breast cancer screening."

In this study, researchers studied 27,578 postmenopausal Iowa women who participated in the Iowa Women's Health Study, a study that was initiated in 1986. A baseline questionnaire was mailed to a random sample of women between the ages of 55 and 69 years with a valid Iowa driver's license in 1986. A follow-up questionnaire collected the data on ethnic background.

The researchers grouped the women in the study into five categories: Scandinavian; English, Scottish, Welsh and Dutch; Irish; German; and other European. Too few women in this Iowa study self-reported their ethnicities as Afro-American, American Indian, Asian or other ethnicities to permit stable estimates of breast cancer risk for these ethnic groups.

The study was published in Cancer Epidemiology, Biomarkers and Prevention.

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