Individuals' data confidentiality was the object of special care, as were ethics towards volunteers and deontology with doctors participating in the study.

The GAZEL cohort received approvals from the National Commission for Data Processing and Freedoms (CNIL), the National Medical Council and the National Consultative Committee of Ethics.

The whole data process has been built following strict confidentiality principles: nobody can access identifying data. Data warehouses are physically separated, and computers are strictly protected. Different anonymity codes are used for each partner and each warehouse.

Questionnaire process

Each year, a follow-up questionnaire is sent to the volunteers, using a trusted third party. This party keeps only names and addresses, and one anonymity number, and has no access to any other data, medical or non-medical.

Data processing with EDF GDF

At regular intervals, different departments from EDF and GDF send data to Inserm, each time using a different anonymity number : Temporary Transfert Number (NTT).

Data processing with the French Health Centers

GAZEL volunteers have been invited to have a complete health checkup in a Health Center (CES). CES are located over the country. During this checkup, blood or DNA samples were taken in order to build a biobank.

Data processing for research projects

After obtaining legal authorizations, the PI of a research project have access to the specific data it requested, using a specific anonymity number (NTT). If the research project requires its own questionnaire, it follows the same anonymous process as the annual GAZEL questionnaire.

The GAZEL cohort is based on EDF-GDF employees’ free and voluntary participation. It is strictly "observational" and does not involve any intervention on the volunteers. Nonetheless, it is necessary to verify that data is used correctly, and that information feedback is sufficient. Different structures and activities have been set up for this purpose

The National commission for data processing and freedoms (CNIL) gave authorizations for all aspects of the GAZEL process. The CNIL quoted GAZEL as an "exemplary" study. Agreements have also been given by the French National Medical Council and the National Consultative Committee of Ethics (CCNE).

In the same way, each new project using the GAZEL cohort data needs to obtain agreement from the relevant authorities.