The role of early life socioeconomic status in female breast cancer incidence

The effect of affluence upon increased breast cancer incidence is a widely studied phenomenon. However, utilizing affluence at time of diagnosis may prove noninformative due to residential mobility and variable socioeconomic status (SES) through an individual's life. Examining a cohort of women born in Utah from 1945-1959, this study seeks to determine whether individual and/or area-based SES at birth is associated with female breast cancer risk in life, and to determine if the incidence of female breast cancer is spatially clustered based on residential location at birth. We utilized Cox proportional hazards (PH) models as a means of determining the impact of SES at birth and adult breast cancer incidence. To examine the potential for spatial clustering patterns at birth, space time scan statistics were run employing 1960 census tracts based on cohort members' residence at birth. Cox PH modeling found that women born into low SES families were less likely to develop breast cancer than women born into the highest SES groups (Q1 HR=0.83 95% CI: 0.72-0.97; Q2 HR=0.81 95% CI: 0.69-0.96). Spatial clustering was limited, though women born in a 2-year time period in South Salt Lake City and the Sugarhouse neighborhood of Salt Lake City exhibited significantly higher risk than their peers (RR=2.2, p-value 0.005). This study seeks to identify mechanisms linking SES at birth to adult breast cancer onset. The findings stress the importance of living and economic conditions at birth and their long-term impacts on breast cancer risk factors and incidence.