Socio-economic factors and breast cancer survival – a population-based cohort study (Sweden) q Magdalena Lagerlund 1, *, Rino Bellocco 1 , Per Karlsson 2 , Go¨ran Tejler 3 & Mats Lambe 1 1 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, SE-171 77 Stockholm, Sweden (where the work was performed); 2 Department of Oncology, Sahlgrenska University Hospital, SE-413 45 Go ¨teborg, Sweden; 3 Department of Surgery, County Hospital of Va ¨stervik, SE-593 81 Va ¨stervik, Sweden Received 11 June 2004; accepted in revised form 15 November 2004 Key words: breast cancer, mortality, socio-economic status, survival, Sweden Abstract Objective: To assess the influence of socio-economic factors on breast cancer survival in Sweden, a country with population-based mammography screening and a uniform health care system aiming to provide care to all on equal terms. Methods: All women with a first diagnosis of invasive breast cancer in Sweden in 1993 were identified in the Swedish Cancer Register. Their sociodemographic characteristics were determined by record linkages to the 1970, 1980, 1985 and 1990 Census databases, and a nationwide Fertility Register. Information on tumor characteristics at diagnosis was obtained from five Swedish Regional Cancer Registers. Survival status on 31 December 1998, was assessed through follow-up in the Swedish Cause of Death Register. Results: Of totally 4645 eligible women diagnosed with breast cancer in 1993, 772 had died from breast cancer through 1998. After adjustment for tumor characteristics and age, risk of death was 37% higher among women of low compared to high socio-economic status (HR high vs. low 0.73; 95% CI: 0.54–0.99). This difference was most pronounced in women less than 50 years at diagnosis. Conclusions: These results show that socio-economic disparities in breast cancer survival prevail even in this relatively homogenous society, offering outreach mammography and standardised treatment regimens in a tax- funded health care system. Introduction Epidemiological findings indicate that both breast can- cer incidence and survival are related to socio-economic factors. Women of lower socio-economic status are at lower risk of developing breast cancer [1, 2], but tend to have poorer survival [3–22] compared to more socio- economically favoured women. The social difference in breast cancer incidence has been attributed to differ- ences in reproductive behaviour; in general women of higher socio-economic status have lower parity, a higher age at first birth, greater prevalence of childlessness, a shorter duration of breast-feeding and a later age at menopause – all factors that are known to increase the risk of breast cancer [23]. Less is known about the aetiology of social differences in breast cancer survival. Suggested factors of importance include not only the timing of the diagnosis, but also the type and quality of treatments offered and received, the biological profile of the neoplasm and individual patient characteristics such as co-morbidity and psychosocial factors [3]. The aim of this study was to assess breast cancer survival in relation to different socio-economic indicators after adjustment for tumour characteristics among women diagnosed in 1993, when outreach mammogra- phy screening programs had been established in 21 of 24 Swedish counties (where 95% of the total female *Address correspondence to: Magdalena Lagerlund, Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, SE-171 77 Stockholm, Sweden. Ph.: + 46-8-524-8-6166; Fax: + 46-8-31-4957; E-mail: Magdalena.Lagerlund@meb.ki.se q Financial support: This study was supported by the Swedish Council for Social Research (grant No. 97-0221), Karolinska Institutet Research Funds and the Swedish Cancer Society. Cancer Causes and Control (2005) 16:419–430 Ó Springer 2005 DOI 10.1007/s10552-004-6255-7