Lung cancer and socioeconomic status in a pooled analysis of case-control studies

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. 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. 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)). SES remained a risk factor for lung cancer after adjustment for smoking behavior. Funding: This study was supported by the German Social Accident Insurance, grant number FP 271. Grant sponsors of the individual studies were the Canadian Institutes for Health Research and Guzzo-SRC Chair in Environment and Cancer, National Cancer Institute of Canada, Canadian Cancer Society, Occupational Cancer Research Centre, Workplace Safety and Insurance Board, Canadian Cancer Society, and Cancer Care Ontario; Grant sponsor: European Commission’s INCO Copernicus program; Grant number: IC15-CT96-0313; Grant sponsor: European Union Nuclear Fission Safety Program; Grant number: F14P-CT96-0055; Grant sponsors: French Agency of Health Security (ANSES), Fondation de France, French National Research Agency (ANR), National Institute of Cancer (INCA), Fondation pour la Recherche Medicale, French Institute for Public Health Surveillance (InVS), Health Ministry (DGS), Organization for the Research on Cancer (ARC), and FrenchMinistry of work, solidarity, and public function (DGT); Grant sponsor: Federal Ministry of Education, Science, Research, and Technology; Grant number: 01 HK 173/0); Grant sponsor: Federal Ministry of Science; Grant number: 01 HK 546/8; Grant sponsor: Ministry of Labour and Social Affairs; Grant number: IIIb7-27/13; Grant sponsor: Research Grants Council of the Hong Kong Special Administrative Region, China; Grant number: CUHK4460/03M; Grant sponsors: Environmental Epidemiology Program of the Lombardy Region, INAIL, Italian Association for Cancer Research, Region Piedmont, Compagnia di San Paolo, Lazio Region, Health Research Council of New Zealand, New Zealand Department of Labour, Lottery Health Research, Cancer Society of New Zealand; Grant sponsor: Polish State Committee for Scientific Research; Grant number: SPUB-M-COPERNICUS/P-05/DZ-30/99/2000; Grant sponsors: Instituto Universitario de Oncologia, Universidad de Oviedo, Asturias, Fondo de Investigacion Sanitaria (FIS) and Ciber de Epidemiologia y Salud Publica (CIBERESP), Swedish Council for Work Life Research and Swedish Environmental Protection Agency, Dutch Ministry of Health, Welfare and Sports, National Institute of Public Health and the Environment, and Europe Against Cancer Program, Roy Castle Foundation, and Intramural Research Program of the National Institutes of Health, National Cancer Institute, Division of Cancer Epidemiology and Genetics, Bethesda, Maryland.