SAHSU maintains a large data collection of health records and population-based data that are used to study trends in chronic disease including environmental risk factors. Our research is used to protect the health of the population and to support improvements in health and care outcomes. Having data on the entire population is essential to allow us to investigate national environmental health concerns, conduct disease surveillance and detect disease clusters.

Our health data collection consists of the following:

  • Hospital Episode Statistics (HES) - All admissions Admitted Patient Care, Critical Care and Accident and Emergency attendances at NHS hospitals in England
  • Cancer registrations (England and Wales)
  • ONS deaths, live births and still births registrations
  • British Isles Network of Congenital Anomaly Registers
  • Scottish births, mortality and congenital anomalies

Major and unique features of SAHSU are the range of both environmental and health data held and our expertise in handling health data at small area (neighborhood) level. Our national health datasets currently contain over 600 million patient records. These are held in a secure, private stand-alone network referred to as 'SAHSU Secure Research Systems' (SSRS). Our data fields include postcode or address of residence (there are currently ~1.7 million residential postcodes in use in the UK) and these fields are held in an encrypted format with restricted access. We need geographical information on place of residence to accurately investigate disease and health risks in neighborhoods (small areas) and to detect disease clusters.

Our health data come from a number of data providers including national records collected by the Office for National Statistics (ONS), the Welsh Cancer Intelligence & Surveillance Unit (WCISU), NHS Digital and other national sources. These data holdings are updated regularly on an on-going basis, with ONS, WCISU and HES data updated on an annual basis. Other health data are updated as required for specific studies.

Ethical and governance permissions to hold and use health data for environmental health research have been obtained from the following authorities:

  • Health Research Authority - National Research Ethics Service (NRES)
  • Health Research Authority- Confidentiality Advisory Group (CAG) which advises on Regulations 5 of the Health Service (Control of Patient Information) Regulations 2002 to process patient identifiable information without consent
  • PHE Caldicott Advisory Panel which advises on Regulation 3 of the Health Service (Control of Patient Information) Regulations 2002 to process patient identifiable information without consent

Non-health data

SAHSU additionally hold small area data from the national Census on populations and socio-economic status (SES), including enumeration district, census output areas, lower layer super output areas, wards (see Table of Social factor data). We also hold environmental data from a range of sources (see Table of Environmental data) including our own research studies, the Environment Agency, Defra, the Civil Aviation Authority, Public Health England, the British Geological Survey and water companies etc. (e.g. see our Environment and Health Atlas for England and Wales, www.envhealth.co.uk). Maintenance of the databases (health, population, SES and selected environmental data) is conducted by the SAHSU database team.

Table of environmental data

Table of social factor data

Use of data within SAHSU

SAHSU recognises we have a legal and ethical responsibility to handle data which can be of a confidential and sensitive nature carefully and securely, and we are fully committed to doing that in a way that maximises its use while preventing unauthorised or inappropriate use or disclosure. We are respectful of the nature of the data we work with, where it comes from and what it means for individuals.

SAHSU data users are required to manage data, in compliance with information governance requirements and government legislation, and special care is taken with data of sensitive or confidential nature which includes health data.

We ensure the following:

  • Appropriate policies, procedures, accountability, management structures and computing hardware and software are in place to provide a robust governance framework
  • Development of a culture of confidentiality and care when handling information
  • Supporting staff through training - anyone accessing data have to complete both national and internal Data Security and Information Governance (IG) training with annual refresher/updates.

In some cases, for study not funded by Department of Health and Social Care, access to Office for National Statistics (ONS) data will require researchers to go through the Accredited Researcher gateway process and access ONS data from their accredited processor’s site. 

All our research data are held on a stand-alone system the ’SAHSU Secure Research Systems’ (SSRS), an air-gapped stand-alone network with no connection to either the internet or to the Imperial College IT network. with controlled and restricted access. Confidential and sensitive data are held within SAHSU’s secure encrypted database which can only be accessed by the database team. Researchers have access to only pseudonymised data.

We have a robust information governance framework for information management and we have deployed a range of privacy enhancing technologies, physical security measures and audit procedures to provide assurance to our stakeholders that the data assets entrusted to us for our research programme are handled according to rigorous standards.

All researchers using the data are affiliated to SAHSU. New study concepts are initially approved by either the Director or Assistant Director of SAHSU, the SAHSU-Public Health England (PHE) Liaison Committee and have formal minuted approval from the appropriate PHE programme board.

Researchers on the SAHSU research team are required to sign the SAHSU Acceptable Use Policy and Agreement, which includes a written acceptance of the security controls and guideline on the processing of patient data prior to be given access to research data. The level of data access granted is based on the requirements of the study. Research is conducted after SAHSU-PHE approvals, HRA NRES ethical, CAG and the Public Health England Caldicott Advisory Panel approvals are in place. Access to health data are additionally controlled by a series of agreements between SAHSU and our data providers (e.g. Office for National Statistics, NHS Digital, Public Health England, Welsh Cancer Intelligence & Surveillance Unit etc.). Data users may be required to sign to agree to the written terms set by specific data providers.

All studies involving data with any risk of being potential identifiable (e.g. small area level data with small numbers of cases for a particular disease) are conducted within the SSRS environment. We ensure that data are processed as permitted by law, statute and best practice. We follow the national guidelines on disclosure control procedures. We ensure not to publish any material that can potentially identify an individual in research outputs, including tables and maps. SAHSU adheres and conforms to The Office for National Statistics (ONS), data providers and national guidelines to suppress small numbers in all our publications.

SAHSU does not share data with third parties.