LOS ANGELES, Oct. 10 (UPI) -- Estrogen levels in postmenopausal women vary by race, and this may explain differences in the groups' breast-cancer rates, say U.S. researchers.
A study done at the University of Southern California focused on 739 hormone-free postmenopausal women from five ethnic groups: native Hawaiian, Japanese-American, Latina, white and African-American. After adjusting the data to compensate for age, body mass index and other lifestyle factors, several interesting discrepancies emerged.
The first was that native Hawaiians had the highest risk of breast cancer (65 percent higher than whites) and some of the highest levels of circulating estrogens. Japanese-Americans came in second with both measurements.
The researchers noted that breast-cancer rates are rising for both native Japanese and Japanese-American women, adding that this is likely due to lifestyle factors.
Latinas and whites had similar hormone profiles, but Latinas' risk of breast cancer was the lowest of all the groups studied.
Finally, although African-American women have higher estrogen levels and higher rates of breast cancer than whites before menopause and their hormone levels remain higher after menopause, their risk of developing breast cancer drops below that of whites once their menses stop.
The researchers said their work was the largest analysis to date of hormone levels by ethnic group and the first large study to include native Hawaiians and Latinas.
The research appears in the October issue of Cancer Epidemiology, Biomarkers & Prevention.
