SIC was established to determine pathways through which socioeconomic position affects morbidity and mortality, in particular common subtypes of cancer. Data from seven well-established cohort studies from Denmark were pooled. The SIC cohort included just over 83,000 participants aged between 20 and 98 years at baseline. A wide range of behavioural and biological risk factors such as smoking, physical inactivity, alcohol intake, hormone replacement therapy, body mass index, blood pressure, and serum cholesterol were assessed by self-administered questionnaires, physical examinations, and blood samples. All participants were followed up in nationwide demographic and healthcare registries.