By Marilyn J. Borugian et al.
Incidence and mortality rates for most chronic diseases including several types of cancer are higher among people of lower socio-economic status. By contrast, for female breast cancer in developed countries, the relationship may be inverted, with women of higher socio-economic status having higher rates, even when risk factors that differ by socio-economic status such as parity, age at first birth and hormone use are taken into account. Only one earlier study examined the risk of breast cancer in relation to socio-economic status in Canada, and it focused on the effects of passive smoking.
