BACKGROUND: An association between low socioeconomic status (SES) and lung cancer has been observed in several studies, but often without adequate control for smoking behavior. We studied the association between lung cancer and occupationally derived SES, using data from the international pooled SYNERGY study. METHODS: Twelve case-control studies from Europe and Canada were included in the analysis. Based on occupational histories of study participants we measured SES using the International Socio-Economic Index of Occupational Status (ISEI) and the European Socio-economic Classification (ESeC). We divided the ISEI range into categories, using various criteria. Stratifying by gender, we calculated odds ratios (OR) and 95% confidence intervals (CI) by unconditional logistic regression, adjusting for age, study, and smoking behavior. We conducted analyses by histological subtypes of lung cancer and subgroup analyses by study region, birth cohort, education and occupational exposure to known lung carcinogens. RESULTS: The analysis dataset included 17,021 cases and 20,885 controls. There was a strong elevated OR between lung cancer and low SES, which was attenuated substantially after adjustment for smoking, however a social gradient persisted. SES differences in lung cancer risk were higher among men (lowest vs. highest SES category: ISEI OR 1.84 (95% CI 1.61-2.09); ESeC OR 1.53 (95% CI 1.44-1.63)), than among women (lowest vs. highest SES category: ISEI OR 1.54 (95% CI 1.20-1.98); ESeC OR 1.34 (95% CI 1.19-1.52)). CONCLUSION: SES remained a risk factor for lung cancer after adjustment for smoking behavior.

Cancer Care Ontario Occupational Cancer Research Centre Toronto Canada

Dental School College of Medicine Veterinary and Life Sciences University of Glasgow Glasgow United Kingdom

Department of Epidemiology and Public Health Faculty of Medicine University of Ostrava Ostrava Czech Republic

Environmental Epidemiology Division Institute for Risk Assessment Sciences Utrecht University Utrecht The Netherlands

Epidemiology Unit Istituto Dermopatico dell'Immacolata Rome Italy

INRS Institut Armand Frappier Université du Québec Laval Québec Canada

Inserm Centre for Research in Epidemiology and Population Health U1018 Environmental Epidemiology of Cancer Team Villejuif France

Institute for Medical Informatics Biometry and Epidemiology University Hospital Essen Essen Germany

Institute for Prevention and Occupational Medicine of the German Social Accident Insurance Institute of the Ruhr Universität Bochum Bochum Germany

Institute for Statistics University Bremen Bremen Germany

Institute of Carcinogenesis Russian Cancer Research Centre Moscow Russia

Institute of Environmental Medicine Karolinska Institutet Stockholm Sweden

Institute of Epidemiology 1 Helmholtz Zentrum München Neuherberg Germany

Institute of Hygiene and Epidemiology 1st Faculty of Medicine Charles University Prague Czech Republic

Institute of Medical Statistics and Epidemiology Technical University Munich Munich Germany

International Agency for Research on Cancer Lyon France

Laboratory of Public Health and Population Studies Department of Molecular Medicine University of Padova Padova Italy

Leibniz Institute for Prevention Research and Epidemiology BIPS GmbH Bremen Germany

Masaryk Memorial Cancer Institute and Medical Faculty of Masaryk University Dept of Cancer Epidemiology and Genetics Brno Czech Republic

Molecular Epidemiology of Cancer Unit University of Oviedo Ciber de Epidemiologia CIBERESP Oviedo Spain

National Cancer Institute Division of Cancer Epidemiology and Genetics Bethesda United States of America

National Centre for Public Health Budapest Hungary

National Institute of Public Health Bucharest Romania

Palacky University Faculty of Medicine Olomouc Czech Republic

Public Health Ontario Toronto Canada

Regional Authority of Public Health Preventive Occupational Medicine Banska Bystrica Slovakia

Roy Castle Lung Cancer Research Programme Cancer Research Centre University of Liverpool Liverpool United Kingdom

The M Sklodowska Curie Cancer Center and Institute of Oncology Warsaw Poland

The Nofer Institute of Occupational Medicine Lodz Poland

The Tisch Cancer Institute Icahn School of Medicine at Mount Sinai New York New York United States of America

Unit of Cancer Epidemiology Department of Medical Sciences University of Turin Turin Italy

Unit of Epidemiology Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Milan Italy

University of Montreal Hospital Research Center and School of Public Health Montreal Canada

University Paris Sud UMRS 1018 Villejuif France

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