Hospital Episode Statistics data linked to ONS Mortality Records

Date: 07 October 2017

As part of their research on health care markets, IFS researchers sometimes use administrative health records (known as the Hospital Episode Statistics) which are linked to official death registrations.  The description below describes how the data are linked together, why they are needed and how long researchers need to store the data.

The data

  • The Office for National Statistics (ONS) collects information about all deaths registered in England and Wales. This information is collected from official death certificates, and includes the date of death, whether the individual died in an NHS hospital, and the main cause of death.
  • The Hospital Episode Statistics contain information about all visits to NHS Accident and Emergency (A&E) departments and all inpatient admissions to NHS hospitals.
  • Both datasets are anonymised – this means the data do not contain any names or addresses of individuals. Patients are instead represented by strings of numbers and letters that do not reveal the identity of the patient to the researchers working with the data.

The data linkage journey

This is how the process works:

  • NHS Digital, who maintain HES and the mortality data (on behalf of the ONS) create codes for each patient which can be used to link the two datasets together. This means that if an individual who has used an NHS hospital during the period of interest has subsequently died, then they will appear in both datasets.
  • NHS Digital then send three datasets to IFS researchers: (i) A&E and inpatient records from HES for the period between April 2011 and March 2013, (ii) ONS mortality records from January 2011 to December 2015 for patients who used an NHS hospital between April 2011 and March 2013, (iii) a file with codes that can be used to link patients in each file. IFS researchers then put these files together in a secure data area.  This process is followed so that this key data resource can be assembled, while ensuring that patients’ identities are not revealed in the data.
  • More information on the application and data linkage process can be found on the NHS Digital website here:

Why the data are needed

The Hospital Episode Statistics contain records of all admissions, outpatient appointments and accident and emergency attendances at NHS hospitals in England. This is a key dataset used by researchers in many fields to study population health and the organisation of health care in the UK.  Mortality is a commonly studied outcome.  However, HES only contains information on whether a patient dies within the hospital, and no information can be gained on the patient’s wellbeing once they leave hospital.  Linking these records to official ONS mortality data means that patient’s longer-term mortality outcomes can be studied.  This is important as it allows researchers to better understand how different treatments, organisation of care, and an array of targets and regulations, ultimately influence NHS patients’ health.

How long will we keep the data?

Current projects that use these data are expected to run until early 2019.

We will ensure that all records are kept securely over this period of time.