A striking example of a racial difference in the early onset of disease is evident for breast cancer. It is well documented that white women have an overall incidence of breast cancer that is higher than that of blacks. However, the opposite pattern exists under the age of 40, with African American women having a higher incidence of breast cancer than their white counterparts.16 Thus, despite having a lower overall incidence rate of breast cancer compared to their white peers, black women have a higher risk of early onset, severe types of breast cancer and a reduced risk of late-onset types.16 The association of some risk factors with breast cancer varies by age: parity is associated with an increased risk of breast cancer incidence in younger women but a reduced risk in older women.17 Similarly, while obesity is associated with reduced risk in younger women, it is associated with increased risk in older women. Importantly, the cross-over in breast cancer incidence by race persists even after adjustment for risk factors.16 In addition to being more likely to get breast cancer
