Acculturation and Ethnic Variations in Breast Cancer Risk Factors, Gail Model Risk Estimates and Mammographic Breast Density

Abstract

Breast cancer (BC) incidence varies across countries and across US ethnic groups. US Immigrants often exhibit an intermediate level of risk between those observed in their birth country and in the US. This transition of risk may partly be explained by uptake of risk factors associated with acculturation. Investigating whether immigration and acculturation risk patterns are similarly reflected in disease biomarkers can provide insight into mechanisms underlying the transition of risk. We examined differences in the distribution of BC risk factors, absolute risk estimates and mammographic density by ethnicity and acculturation. We used data from 366 women recruited from an urban mammography clinic (ages 40–64 years) to compare BC risk factors and Gail model risk estimates across US-born white, US-born African American [AA], US-born Hispanic and foreign-born Hispanic women. We used linear regression models to examine the associations of immigration and acculturation indicators (e.g., generational status, age and life stage at immigration, language use) with percent density and dense breast area, measured from mammograms. Differences in BC risk factors were mostly observed for ethnic groups, with white women having higher reproductive and lifestyle risk profiles (e.g., lower parity, older age at first birth, higher alcohol intake), Hispanics having shorter height and AAs having larger body mass index (BMI) and waist circumference. The average lifetime and 5-year Gail estimates were highest in whites (11.4% & 1.4%), intermediate in AAs (7.2% & 1.0%) and lowest in Hispanics (6.9% & 0.7% in US-born and 6.6% & 0.8% in foreign-born). After adjusting for age, BMI and parity, lower linguistic acculturation, shorter residence in the US, and later age at immigration were associated with lower percent density (all p values for trend across acculturation levels <0.05); e.g., monolingual Spanish and bilingual speakers respectively had on average 5.6% (95% CI, −10.0–−1.3) and 3.8% (95% CI, −8.1–0.4) lower percent density than monolingual English speakers. Similar but more modest associations were observed for dense area. The increase in BC risk after immigration to the US and subsequent acculturation may operate via influences on mammographic density in Hispanic women.