Hospital Episode Statistics data linked to ONS Mortality Records

IFS researchers sometimes use administrative health records (known as the Hospital Episode Statistics).

As part of their research on health care markets, IFS researchers sometimes use administrative health records (known as the Hospital Episode Statistics) either on their own or linked to official death registrations. The description below describes how the data are linked together, why the data 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 overall aim of the program of work that uses these data is to conduct research into the effects of economics of health and the health care system with the aim to better inform policy makers, practitioners and the general public. This is the purpose of processing these data.

The data can only be used where there is expected measurable benefit to health and social care.

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.

The following publications use the linked data:

"Saving lives by tying hands: the unexpected effects of constraining health care providers"

How long will we keep the data?

We plan to keep the data at our institution as long as we have live projects that use the data. When there are no longer any live projects using the data, we will delete the data according to the data sharing agreement we have in place with NHS digital.

We will ensure that your records are secure for as long as we continue this study.

How do we take care of your data?

Access to these data is extremely restricted and tightly controlled. Only approved researchers working on projects that have been deemed to have public benefit are able to use the data. We will only ever publish non-disclosive outputs which means that it will be impossible to identify you from anything that is published.

We are the sole recipients of the data and the data are not shared with anyone else.

Legal bases for using the data

Our lawful basis for processing these data is: legitimate interests 6(1)(f). Our legitimate interest in question is research and statistical purposes: the conduct of non-commercial, robust social and bio-medical research to inform research, policy and clinical practice.

Because these data contain information about your health, they are classed as Special Category data. Our lawful basis for processing this special category data is:

Article 9(2)j processing is necessary for archiving purposes in the public interest, scientific or historical research purposes or statistical purposes

Your rights

This webpage is designed to inform you how we are using your data.

Because we cannot identify you, it is not possible for us to process other requests in respect of your rights.

If you would like to exercise any of your rights please contact NHS digital. They will deal with your request and any outcome of your request will be passed on to us by them.

If you have complaint you can contact the Information Commissioner’s Office.

Our contact details

If you wish to discuss the way that we use your data, please contact George Stoye @email or you can write to him at

The Institute for Fiscal Studies
7 Ridgmount Street

If you have concerns over the way that we use your data please contact the data protection officer you should email @email or write to them at the above address.