Data about us is collected when we interact with different organisations. Data linkage enables TwinsUK to accurately and confidentially collect information from your official records without disturbing TwinsUK members.  

This has a number of benefits for both TwinsUK members and researchers:  

  • Some may find it difficult to take part in projects at TwinsUK. Data linkage is an easier, effortless way to be involved in vital research.   
  • Even if you have been very active in TwinsUK and attended many visits, there may still be some ‘gaps’ of information in what we know about you. Data linkage can help fill these and create a bigger picture so that we can accurately carry out our research.   
  • Some of the most important information about us is not something we necessarily know or remember. Data linkage helps to collect this information. For example, the precise type and dose of antibiotics you may have been given in the past.  
  • When small amounts of data from individuals are linked up and pooled together, researchers can look for patterns in the data. This helps them to develop new ways of predicting or diagnosing illness and identifying ways to improve care. The information can be used to help understand more about disease risks and causes, improve diagnoses, develop new treatments and prevent disease. 
  • Data linkage enables you to play an important part in TwinsUK and the future of health research. 

Which of my records will you link to? 

TwinsUK has permission to link to your health, education and environmental records. More information about each of these types of linkages is available below. 

Health linkage  

A lot of information that is very useful to TwinsUK researchers is held in your official health records. Health records include those held by your general practitioner (GP) and hospital records, mental health data, cancer registrations and mortality data held by NHS organisations.  

We are bound by the same rules of confidentiality as your GP – your name is never linked to the information taken from your records when used by researchers. Such records may contain information some people find particularly sensitive to disclose openly, for example about mental health or sexual health issues.   

Your patient health information includes:   

  • Details of visits to your doctor, diagnoses made and any treatment you were given.   
  • If you’ve ever been to hospital; why you were there and what happened whilst you were there. This includes visits to accident & emergency, if you were admitted to hospital for care or if you received treatment as an outpatient (e.g. to see a specialist consultant or nurse).   
  • Details of community care you may receive, whether it is for a particular illness or for reasons to do with your mental health.   

If you have opted out of allowing your data to be used for research or planning through your GP surgery or online, then even if you decide to agree to our linkage, we will not be able to do so. You can find out more about the National Opt-out and set your permissions here:     

Education linkage  

Socioeconomic factors, including education and care you may have received, can tell us how your environment may affect your future. There is a strong link between educational attainment and health. Linkage to your education records held by the Department for Education can improve the data we have on your educational background.   

Your education records include:   

  • Your exam results.   
  • Information about your attendance.   
  • Information about support and care you received e.g. if you have a special educational need.   
  • Information about whether you received free school meals.   
  • Specific information about you such as your ethnic group or the languages spoken in your home.   

Environmental linkage  

Your surrounding environment can influence your health and wellbeing. Information about your neighbourhood and environment is derived from your postcode only, from organisations such as the Office of National Statistics (ONS) and the Centre for Hydrology & Ecology (CHE).  

Natural environment and neighbourhood information includes:   

  • Information about your community, such as crime figures, house prices and employment figures.   
  • Information about houses in your neighbourhood, such as insulation levels, house age and house price.   
  • Information about pollution and the type of land around your neighbourhood and where you work.   
  • Information about services around you, such as distance to the nearest GP, parks, libraries and other facilities.   

Case studies 

Below are a few examples of how data linkage has been used and could be used to improve research. 

How data linkage has been used by others 

Clopidogrel is a drug that is recommended for people who have recently had a heart attack. However, it is difficult to know whether people continue to take this for the recommended length of time after they are discharged from hospital and, if they choose to stop taking it, what happens to them. 

Researchers linked together three sets of data to try to understand more about what happens to people once they are discharged from hospital, after receiving treatment for a heart attack. They linked records of someone’s treatment and prescriptions in hospital with GP data showing what happened to them after discharge. They then linked these to national records of individual deaths.  

The research demonstrated that stopping taking clopidogrel is common, and that this is associated with an increased number of heart attacks and death. However, while the research demonstrated an association, it could not prove a causal link. Future research will continue to investigate this. 

You can find out more by visiting 

How data linkage could improve TwinsUK research methods 

Mrs Jones is a twin in our study. One morning she received an email asking her to complete an online questionnaire from TwinsUK about antibiotic use in her life so far. The study was looking at the effect of antibiotic use over our lives on our gut microbes and on health conditions such as obesity and type 2 diabetes. Like most people, Mrs Jones had not kept notes on her antibiotic use throughout her life.  

With data linkage, we would be able to see when exactly Mrs Jones has been prescribed antibiotics, which type, and for how long, much more easily and accurately. This would give us better quality data for our research study, and without needing to disturb Mrs Jones. 

How data linkage could benefit TwinsUK research 

Twins have joined the TwinsUK registry at different points since it was set up in 1992. Even if twins attended all of their twin visits, we would only have a few weight and blood pressure measurements for them since they joined the TwinsUK registry. 

By linking to other health records however like those held by a twin’s GP, we would be able to see more weight and blood pressure measurements taken throughout their lifetime. This would help us fill in any gaps in our data from twins who joined TwinsUK later on, or those who are no longer able to attend visits in person. We would also be able to look further back to weight and blood pressure measurements from before the twins joined TwinsUK. This would give us a lot of valuable information for our research. 

How will you link to my records? 

We will securely share identifiers such as your name, date of birth and NHS number with official organisations that hold your records. They will then provide us with the linked data. The data is imported into our database with any information that could directly identify you removed. The data is linked with your current TwinsUK pseudonymised data using a unique, number. The data will be kept in a secure research environment controlled by the Department of Twin Research, King’s College London.  

The figure below describes how data moves between the different organisations: 

The UK Longitudinal Linkage Collaboration (UK LLC) 

TwinsUK is one of many population cohort studies in the UK. During the COVID-19 pandemic, TwinsUK united with other cohorts in the UK to pool together our data in order to advance COVID-19 research, through the UK Longitudinal Linkage Collaboration. The data is held securely at the University of Swansea and managed by the University of Bristol.     

Now, the UK LLC is expanding to allow researchers to study research questions beyond COVID-19. The UK LLC will hold research data that cohorts choose to share on their participants and link to health, environmental, education and administrative records depending on each study’s permissions.  

TwinsUK will share some of our data sets with the UK LLC, and allow the UK LLC to link to participants’ health, education and environmental records according to your preferences as indicated on your TwinsUK consent form. All participants’ data held in the UK LLC will be de-identified at all stages, meaning that researchers and the UK LLC staff cannot identify anyone from the data.     

Researchers can apply to use any of the data held in the UK LLC. TwinsUK will retain complete control over who accesses TwinsUK data. The TwinsUK Resource Executive Committee will review every request to use TwinsUK data and only allow access to bona fide researchers carrying out health research for the public good. In this way, TwinsUK retains complete control over who accesses TwinsUK datasets and linked data. 

You will be included in the UK LLC based on your linkage preferences indicated through your consent form.  

More information about the UK LLC is available on their website:   

Who will have access to my health, education and environmental data? 

The information from your health, education and environmental records can be used to help understand more about diseases. But TwinsUK can’t do all the data analysis on its own. We work in partnership with researchers from across the health research spectrum, including academic institutions, charities and regulators, provided the research is in the public interest and is governed by data sharing agreements. The results of the research must be made public.  

Researchers from outside of TwinsUK may ask us for permission to use the data we hold. The TwinsUK Resource Executive Committee (TREC) reviews each and every one of these requests carefully, and only bona fide researchers approved by King’s College London and working for the public good are granted access. We will never share your personal data such as name or date of birth.  

As described above, researchers will also be able to request access to TwinsUK data, including linked health, education and environmental records through the UK LLC. Each request to use TwinsUK data will be reviewed by TREC. 

We will not share your linked health, education and environment data with commercial companies. 

What are the risks of data linkage? 

The way we keep your health, education and environmental data is regulated in order to make any risks as low as possible. 

Possible risks and the steps we take to reduce them include: 

Invasion of privacy, or personal information being revealed to others 

  • All our data is held on secure servers. Your personal data (name, date of birth and address) is kept completely separately and is only ever accessible by a very small number of individuals in the core TwinsUK team for the purpose of contacting you and recruiting you to studies. 
  • Research data (for example our questionnaire and visit data and linked health data) does not include your name and contact details. 
  • Research data can only be accessed by bona fide, approved researchers. 
  • There is a clear audit trail showing who has accessed the data and when. 
  • Only the minimum amount of information necessary is passed onto any researcher relevant for their specific research. 
  • We treat it as a potential criminal offence to misuse personal data, including trying to re-identify someone without permission. 

Loss of control if data is passed outside TwinsUK 

  • Sharing of health records data must be in accordance with data security protection standards and stipulations by NHS Digital and are subject to audit. 
  • TwinsUK will never share data linked with your personally identifiable data. 
  • Whoever the user, there are regulations to access your data. Researchers have to sign contracts setting out what they can and cannot do with the data, including limits on passing data onto third parties. Data must be stored securely, with controlled access and robust IT systems to keep data safe, and there are strong sanctions if data is misused. 

How can I take part in data linkage or opt out? 

If you have signed up to TwinsUK or taken part in our studies since 2021, you will have had the chance to indicate your linkage preferences on the TwinsUK consent form.  

If you signed up to TwinsUK before 2021 and haven’t taken part in any studies or visits since 2021, you will have received a Decision Form to indicate your linkage preferences in spring 2021. If you indicated you did not wish to take part in data linkage through this Decision Form, you will not be included. If you did not respond to the Decision Form, TwinsUK will be able to link to your records until you tell us otherwise. 

We will always respect your decision, and you may contact us at any time to check your linkage status and change which of your data we link to.  

Due to logistical constraints, your linkage preferences will apply to both TwinsUK’s ability to link to your records as well as the UK LLC. For example, if you agree to health and education records linkage, both TwinsUK and the UK LLC will be able to link to your health and education records. If you set your preferences to not allow linkage to your environmental records, neither TwinsUK nor the UK LLC will be able to link to your environmental records. 

National opt-out 

If you have opted out of allowing your data to be used for research or planning through your GP surgery or online, then even if you decide to agree to our linkage, we will not be able to do so. You can find out more about the National Opt-out and set your permissions here:  

Who can I contact for further information? 

If you have any questions or concerns, please contact the TwinsUK team on the details below and we will be happy to help. 

020 7848 4444 

Department of Twin Research 

4th Floor South Wing D Block 

St Thomas’ Hospital Campus 

Westminster Bridge Road