Social inequality and incidence of and survival from cancer in a population-based study in Denmark, 1994–2003: Background, aims, material and methods Susanne Oksbjerg Dalton a, * , Marianne Steding-Jessen a , Mette Gislum b , Kirsten Frederiksen a , Gerda Engholm b , Joachim Schu ¨z a a Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark b Department of Cancer Prevention and Documentation, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark ARTICLE INFO Article history: Received 27 May 2008 Received in revised form 6 June 2008 Accepted 16 June 2008 Available online 4 August 2008 Keywords: Cancer incidence Survival after cancer Socioeconomic position Denmark Social inequality ABSTRACT The purpose of this register-based study was to identify variations in cancer incidence and survival after cancer in Denmark on the basis of a range of socioeconomic, demographic and health-related indicators. The indicators were level of education, disposable income, affiliation to the work market, social class, housing tenure, size of dwelling, cohabitation status, type of district, ethnicity, Charlson comorbidity index, depression and schizophre- nia measured at the individual level on an annual basis. The study population comprised all Danish residents born between 1925 and 1973 and aged P30 years, who were followed up for cancer incidence in 1994–2003 and for survival in 1994–2006. The study was based on 3.22 million persons, yielding almost 26 million person-years and 147,973 cancers. In this paper, we provide a detailed description of the indicators and the statistical methods, and we discuss the strengths and limitations of our approach. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Numerous studies have revealed consistent associations be- tween social position and health; however, associations be- tween markers of social position and the incidences of different cancers are much more heterogeneous. For in- stance, low social position, measured as educational level, occupational status or income, has been associated with in- creased risks for cancers of the cervix, head and neck, lung and stomach and lower risks for cancers of the breast, pros- tate and colon and malignant melanoma. 1–6 Although the available information is sparse, longitudinal data suggest that social class differences in the risks for some types of cancers are increasing with time. 1 Socioeconomic differences in can- cer incidence can presumably be partly explained by known risk factors, such as smoking, occupational exposure, repro- ductive behaviour and biological agents (human papilloma virus, Helicobacter pylori, hepatitis B and C viruses), although only a limited number of epidemiological studies have ad- dressed this hypothesis directly. 7–13 Evidence for socioeconomic differences in survival has been found for many cancers and in many populations 14–16 : more socially disadvantaged patients have consistently poorer survival than those who are better off. The differ- ences may be related to differences in the time of diagnosis, in the biological characteristics of the tumour, in the treat- ments given or in patient-specific factors, such as lifestyle or the presence of comorbid conditions. An extensive review of studies of socioeconomic differences in cancer survival published within the last decade (since 1995) concluded that 0959-8049/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ejca.2008.06.010 * Corresponding author: Tel.: +45 35257500; fax: +45 35257731. E-mail address: sane@cancer.dk (S.O. Dalton). EUROPEAN JOURNAL OF CANCER 44 (2008) 1938 – 1949 available at www.sciencedirect.com journal homepage: www.ejconline.com