Influence of socioeconomic factors on survival after breast cancer—A nationwide cohort study of women diagnosed with breast cancer in Denmark 1983–1999

Abstract

The reasons for social inequality in breast cancer survival are far from established. Our study aims to study the importance of a range of socioeconomic factors and comorbid disorders on survival after breast cancer surgery in Denmark where the health care system is tax-funded and uniform. All 25,897 Danish women who underwent protocol-based treatment for breast cancer in 1983-1999 were identified in a clinical database and information on socioeconomic variables and both somatic and psychiatric comorbid disorders was obtained from population-based registries. We used Cox proportional hazards models to estimate the association between socioeconomic position and overall survival and further to analyse breast cancer specific deaths in a competing risk set-up regarding all other causes of death as competing risks. The adjusted hazard ratio (HR) for death was reduced in women with higher education (HR, 0.91; 95% confidence interval (CI), 0.85-0.98), with higher income (HR, 0.93; 95% CI, 0.87-0.98) and with larger dwellings (HR, 0.90; 95% CI, 0.85-0.96 for women living in houses larger than 150 m(2)). Presence of comorbid disorders increased the HR. An interaction between income and comorbid disorders resulting in a 15% lower survival 10 year after primary surgery in poor women with low-risk breast cancer having comorbid conditions ( approximately 65%) compared to rich women with similar breast cancer prognosis and comorbid conditions ( approximately 80%) suggests that part of the explanation for the social inequality in survival after breast cancer surgery in Denmark lies in the access to and/or compliance with management of comorbid conditions in poorer women.