Cohort profile: the GAZEL Cohort Study.

Electricite de France-Gaz de France (EDF-GDF) is the only utility firm in France involved in production, transmission and distribution of energy. For several reasons, EDF-GDF is a unique setting for epidemiology. The company employs about 150 000 workers in all regions of France, from large cities to small villages; there is a wide socioeconomic range of occupational positions, including white and blue-collars workers. The workforce is very stable: due to their civil servant-like status, employees almost never leave the company and are not lost to follow-up even after retirement, since retirement benefits are paid by the company itself. An extensive human resources system allows for a complete follow-up of the workers, even when they retire. EDF-GDF has its own Occupational Health and Social Security system; about 300 physicians work for the company and are responsible for the health surveillance of the workers. During the seventies the medical department of EDF-GDF decided to build a comprehensive database on the health of the workforce. The database was designed in close collaboration with researchers at INSERM—the French National Institute for Health and Medical Research—Research Unit 88, directed at that time by one of us who was also a Scientific advisor for the medical department of the company (MG). The database contained demographic, socioeconomic and professional data on each worker. An exhaustive register of sick leave, accidents, permanent disabilities, compensated diseases, causes of death, cancer and coronary heart disease incidence among active workers was created. Further, a job-exposure matrix was established for 30 potentially carcinogenic agents. 1,2 Using these databases several epidemiological studies on working accidents, sick leave, cancer and mortality were carried out. However the absence of individual level data on lifestyle, self-reported health conditions and the social environment limited the ability to study numerous research questions in-depth. With the aim of overcoming some of these shortcomings, researchers at INSERM designed a new project to develop a longitudinal cohort made of a sample of volunteer EDF-GDF workers: the GAZEL Cohort Study (GAZEL stands for GAZ and ELectricite). The management, the unions and the medical department of EDF-GDF gave their consent to the project, and the company accepted to provide regular access to all personal and health data files. EDF-GDF and the worker’s social activities organization decided to fund INSERM Unit 88 for the major part of the GAZEL Cohort Study costs on a regular basis; regular funding came also from INSERM Unit 88’s own budget, and specific funding for the setting up of a biobank came from private foundations (Fondation de France and Association pour la recherche sur le cancer). These resources allow only for the basic functioning of the cohort and all specific research projects must find their own additional funding. The GAZEL Cohort Study was launched in January 1989. INSERM Unit 88 (now Unit 687: Public Health and Epidemiology of Occupational and Social Determinants of Health) manages the project and has had full responsibility for it since the beginning, without any interference from the company in relation to the scientific work or publication of results.