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SNDS — Système National des Données de Santé

Overview

The Système National des Données de Santé (SNDS) is the French national health data infrastructure, created by the Law of 26 January 2016 (loi de modernisation du système de santé, article 193). It consolidates health insurance reimbursement data (SNIIRAM), hospital discharge records (PMSI), causes of death (CépiDC), and disability data (MDPH/CNSA) for over 65 million people, covering virtually the entire French population. Since the decree of 29 June 2021, CNAM (Caisse Nationale de l’Assurance Maladie) and the Health Data Hub are joint data controllers (responsables conjoints de traitement) of the SNDS, with CNAM managing the core infrastructure and the HDH facilitating project-based access. It is a central resource for large-scale epidemiological, pharmacoepidemiological, and health policy research in France, and is designated under EHDS as the country’s reference dataset for secondary use obligations.

Scope and Coverage

The SNDS covers approximately 99% of French residents, with longitudinal follow-up possible from 2003 onwards. Since October 2022, a larger representative sample called the ESND (Échantillon des données du SNDS) is available for lighter research use, replacing the earlier EGB (Échantillon Généraliste des Bénéficiaires) at 1/97th of the population.

The SNIIRAM component contains health insurance reimbursement data covering consultations, prescriptions, medical acts, biological tests, and medical devices for ambulatory care. The PMSI (Programme de Médicalisation des Systèmes d’Information) provides hospital stay records covering diagnoses, procedures, and GHM groupings across all French hospitals, organised into four sectors: MCO (acute care), SSR (rehabilitation), HAD (home hospitalisation), and psychiatry. PMSI data is collected by ATIH (Agence Technique de l’Information sur l’Hospitalisation). CépiDC provides cause-of-death data from INSERM’s Centre d’Épidémiologie sur les Causes Médicales de Décès. The MDPH/CNSA component covers disability compensation and care from the Maisons Départementales des Personnes Handicapées, with partial linkage to the rest of the SNDS.

Data Access

Access is regulated under the French Code de la Santé Publique (articles R. 1461-1 onwards) and overseen by CNAM, the Health Data Hub, and CNIL.

Permanent access is granted by decree to specific public bodies with a public health or research mission, including CNAM, DREES, Santé publique France, HAS, ANSM, ATIH, ANAP, and affiliated structures such as EPI-PHARE (a joint CNAM/ANSM pharmacoepidemiology unit). These bodies access data directly via CNAM’s secure environment.

Project access is available to academic and industry researchers. It requires a favourable opinion from CESREES (Comité Éthique et Scientifique pour les Recherches, les Études et les Évaluations dans le domaine de la Santé), an authorisation from CNIL, submission via the Health Data Hub portal, and processing in the HDH Datalab, a secure environment from which no data can be exported.

Simplified access is available via CNIL reference methodologies (méthodologies de référence), notably MR-007 for non-interventional studies reusing already-collected health data, allowing conformity declarations in place of full CNIL authorisation for pre-approved study types. Data in the SNDS is pseudonymised but not anonymised, and re-identification of individuals is strictly prohibited.

Coding and Terminologies

Diagnoses in PMSI and CépiDC are coded using CIM-10 (ICD-10). Hospital procedures are coded using CCAM (Classification Commune des Actes Médicaux). Ambulatory acts are coded using NGAP (Nomenclature Générale des Actes Professionnels), covering general medicine, nursing, and paramedical acts. Biological acts reimbursed via SNIIRAM are coded using NABM (Nomenclature des Actes de Biologie Médicale). Dispensed drugs are identified via CIP (code identifiant de présentation) and CIS codes, which can be linked to the ATC classification through drug reference databases such as Thériaque or BCB. Hospital stays in PMSI-MCO are grouped using GHM (Groupes Homogènes de Malades), the French DRG equivalent.

Standards and Interoperability

The Health Data Hub is working on transforming SNDS extracts to OMOP CDM to support federated research. This is a project-level mapping initiative and not a native SNDS standard. HL7 FHIR is promoted by ANS (Agence du Numérique en Santé) for future health system interoperability but is not the native format of SNDS. Under EHDS, which was published in the EU Official Journal on 5 March 2025 and requires member states to designate Health Data Access Bodies by March 2027, the Health Data Hub is France’s expected HDAB candidate, and the SNDS is the primary reference dataset for French secondary use obligations.

Connections

  • Joint data controllers: CNAM and Health Data Hub (since decree of 29 June 2021)
  • Ethical and scientific oversight: CESREES
  • Data protection authority: CNIL
  • European context: EHDS

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