Early Life Exposures and Breast Cancer Risk Among African-American and European-American Women
Glasgow, Mark Louis
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Introduction There is evidence to suggest that early life exposures including birth weight, history of having been breastfed in infancy, in utero exposure to maternal smoking, and parental education are associated with breast cancer risk. Potential underlying mechanisms include variability in exposure to maternal endogenous sex and growth hormones. Also, parental socioeconomic status may be a proxy for environmental characteristics that impact biological processes in early life, and ultimately influence breast cancer risk. Research has focused on European-American (EA, alternatively used for "European American" where appropriate) women, and relatively little is known about associations between early life exposures and breast cancer risk for African-American (AA, alternatively used for "African American" where appropriate) women. Methods We conducted a case-control study in AA and EA women aged 22-75 years living in metropolitan New York City and eastern New Jersey (Women's Circle of Health Study). Breast cancer cases (AA n=987; EA n=772) were diagnosed with primary, incident, histologically confirmed invasive breast cancer or ductal carcinoma in situ. Controls (AA n=958; EA n=715) were frequency matched to cases on age and race. Birth weight, history of having been breastfed in infancy, history of in utero exposure to maternal smoking, and parental education were by self-report using an interviewer-administered questionnaire. Results For both racial groups, birth weight was not associated with breast cancer risk. Having been breastfed in infancy was associated with significantly increased breast cancer risk for both racial groups (ORAA=1.58, 95% Cl: 1.27-1.97; OREA=1.44, 95% Cl: 1.13-1.84). For EA women, but not AA women, reporting in utero exposure to maternal smoking was associated with significantly decreased breast cancer risk (OR=0.61, 95% Cl: 0.45-0.82). Among AA women, those born to mothers with at least a college degree had a significantly lower breast cancer risk compared to AA women born to mothers with a high school or less education (OR=0.66, 95% Cl: 0.49-0.91). Among EA women, we found no association with maternal education. However, EA women born to fathers with at least a college degree had a significantly lower breast cancer risk compared to EA women born to fathers with a high school or less education (OR=0.64, 95% Cl: 0.50-0.83). Conclusion Our findings provide support that some early life exposures potentially impact adult breast cancer risk. History of having been breastfed in infancy, no history of in utero exposure to maternal smoking, and less parental education were found to be associated with greater breast cancer risk. No racial differences were found.