The Caerphilly Prospective Study (CAPS) was set up by the MRC Epidemiology Unit (South Wales). At that time it was the fifth prospective study of cardiovascular disease in the United Kingdom, although only the second population based study, after the British Regional Heart Study.

Its initial aims were to examine the importance of lipids,haemostatic factors, and hormones such as testosterone, cortisol and insulin (Lichtenstein et al 1987) in the development of ischaemic heart disease (IHD). Subsequently, other hypotheses were included with a specific interest in platelet function, and psychosocial variables.

With the ageing of the cohort, additional outcomes have been included in particular stroke, hearing problems and cognitive function.

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Phase I

The initial design attempted to contact all men aged 45 to 59 years from the town of Caerphilly and adjoining villages.  2512 subjects (response rate 89%) identified from the electoral register and general practice lists were examined between July 1979 until September 1983 (phase I).

Men were initially seen at an evening clinic, where they completed a questionnaire, had anthropometric measures and an ECG taken. They also completed a food frequency questionnaire at home (Fehily et al 1994). They subsequently re-attended an early morning clinic to have fasting blood samples for a wide variety of tests.

Quality control was examined by the use of both "blind" split samples as well as a second repeat measure on a random sub-sample to examine intra-individual variation.

Phase I variables.

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Phase II

Phase II was undertaken between July 1984 to June 1988. An additional 447 new men were included who had moved into the study areas. In addition to the tests undertaken at phase I, new tests included audiometry.

Phase II variables.

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Phase III

Phase III was undertaken between November 1989 to September 1993. It followed the same methods as before. The main new features were a standardised battery of cognitive function tests as well as a variety of new platelet and bleeding time tests.

Phase III variables.

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Phase IV

Phase IV, the last time the men were examined, was undertaken between October 1993 to February 1997. Audiometry measured at phase II was repeated as was cognitive function measured at phase III.

All men have been followed up for incident IHD through mortality flagging, self-reported information confirmed by medical records, positive history to the Rose angina questionnaire, checking hospital admissions and new evidence of ECG ischaemia. The WHO criteria were used to define cases of non-fatal myocardial infarction.

At each phase, 40-50 mls of blood were taken and stored at either -40 or -80 C. This insightful decision has enabled subsequent researchers to rapidly test new hypotheses (e.g. the role of H. Pylori, cytomegalovirus and C. Pneumoniae with respect to IHD risk: see Strachan et al 1999, 1999, 1998).

A large amount and variety of samples (serum, plasma, sodium citrate, etc.) remain for future potential analyses. Unfortunately, no whole blood was stored from phase I.

Phase IV variables.

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Follow-up research

Since that time the men have been contacted on two further occasions by post. This has enabled data on stroke events as well as new non-fatal myocardial infarctions to be collected.

Clinical records of all strokes have been studied in detail and CT scans obtained where possible. In the most recent follow-up, standardised data on disability and functional limitation was included to derive a measure of healthy ageing (Ebrahim and Kalache 1996).

All deaths and cancer registrations are flagged (NHSCR) and added to the database. The research from the MRC Caerphilly Prospective Study has already resulted in around 150 publications and this will continue to increase as currently there are three funded research projects in progress.

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Privacy notice

The data we have collected on you for the Caerphilly Prospective Study (CaPS) is to enable us to look at what risk or protective factors may be associated with a wide range of chronic diseases, such as heart disease, stroke, dementia etc. We have a wide range of different types of data; (a) questionnaire – either self-report or responses to an interviewer, (b) clinic measurements - things like weight or blood pressure, (c) biomarkers – measures derived from a blood sample such as cholesterol or genetic variations (d) cognitive function tests of memory (e) outcome data such as whether you have had a heart attack from medical records or other sources.

We take data security very seriously and adhere fully to the University of Bristol’s data protection and information security policies and procedures. University of Bristol is the Data Controller, and is responsible for ensuring that all data are securely stored, handled and used in accordance with the Data Protection Act 2018 and General Data Protection Regulation (GDPR). University of Bristol data policies and procedures comply with legislative and regulatory requirements, including NHS standards. The principal investigator remains the Data Custodian and oversees the way in which the study members’ data are looked after.

All contact information, such as names, addresses and telephone numbers of study members, is stored on an IT network that is protected by digital access controls, firewalls, security testing, full auditing, and other security provisions, to protect against the risk of unauthorised access. This system is also physically locked down and is only accessible by authorised personnel.

The same security measures are applied to all data that has been collected on study participants, be it questionnaire, clinical data or from any blood samples. All participants are coded with an arbitrary reference number, which means that researchers analysing results cannot directly identify participants and never see any contact information. Similarly, any data that is shared with research collaborators is fully anonymised to protect confidentiality and only used for approved ethical research purposes. All paper records are kept locked away in a secure storage area with restricted access. We will keep your data until we feel it no longer can add to our scientific knowledge and help society. At this moment this will review the value of the study again in 2025 at which point we will decide if we should continue to look after the data for longer or destroy it.

The legal basis for personal data to be obtained and processed for this purpose is Article 6 (1) (e) of the GDPR, which covers processing that is necessary for the performance of a task carried out in the public interest. The legal basis for processing information about particpants’ health is Article 9 (2) (i), which covers processing that is necessary for reasons of public interest in the area of public health, and Article 9 (2) (j) that covers processing that is necessary for reasons of public interest in the area of research.

Participants whose data is being processed have certain rights over their data. Further details can be found in the University of Bristol’s Data Protection Policy. Anyone who believes their data is being processed in a way that isn’t fully compliant with requirements has the right to submit a complaint to the Information Commissioner’s Office.

Any queries about the University of Bristol’s compliance with data protection requirements should be directed to data-protection@bristol.ac.uk or (0117) 3941824.

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Steering committee

The MRC awarded Professor Stephen Frankel a grant to enable all the resources from the MRC Unit to be transferred to the Department of Social Medicine, University of Bristol, from April 1999 on the closure of the Unit.

All paper records have been archived and blood samples catalogued.

All the electronic data (existing in around 600 flat files) were re-imported into a specially designed relational database.

This has enabled a wide range of on-going research projects to continue as well as enabling new collaborators to continue to work on the data and biological samples.

Any individual interested in having access to materials from the Caerphilly study should read the terms and conditions for potential collaborators and discuss the matter initially with Professor Yoav Ben-Shlomo.

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History of the MRC Epidemiology Unit in South Wales

Between 1936 and 1942 Philip D ;Arcy Hart co-ordinated, on behalf of the MRC,a series of surveys of chronic pulmonary disease in South Wales coal miners to address the growing concerns about the respiratory health of miners.[1]

To investigate further the causes of lung disease in miners the MRC established the MRC Pneumoconiosis Research Unit at Llandough Hospital in 1945.[2]

In 1948 Dr Archie Cochrane joined the unit and established a team carrying out what he called 'clinical and environmental studies'. During the 1950s this team was largely concerned with epidemiological studies of respiratory disease in miners. They did, however, carry out electro-cardiographic surveys and studies of blood pressure at the behest of Dr Bill Miall.

In 1960 Cochrane became the David Davies Professor of Tuberculosis and Chest Diseases at the Welsh National School of Medicine and the MRC agreed toseparate his team to create an MRC Epidemiology Unit in South Wales.[3] In 1974 on the retirement of Cochrane, Dr Peter Elwood took over until his own retirement in 1995, at which point a decision was made to close the Unit.

Mr Peter Sweetnam took running the Unit until the end of March 1999 when the Unit closed. In addition to work on mining communities, the Unit carried out studies of other industrial workers, iron deficiency anaemia, migraine, eye disease, aspirin, environmental lead, milk supplementation, and cardiovascular disease.

Perhaps the most influential study the Unit carried out was the randomised-controlled trial of aspirin, which showed for the first time that daily aspirin might reduce mortality following myocardial infarction.[4] The paper describing the results of this study was among the fifty most cited papers published in the British Medical Journal.[5]


  1. D’Arcy Hart P with Tansey EM. Chronic pulmonary disease in South Wales coal mines: an eye-witness account of the MRC surveys (1937-1942) Social History of Medicine 1998; 11: 459-468.
  2. Perspectives on the role of the MRC Eds: Austoker J, Bryder L.. Oxford: Oxford University Press, 1989 pp. 137-161.
  3. Cochrane AL, with Blythe M. One Man’s Medicine British Medical Journal: London 1989.
  4. Elwood PC, Cochrane AL, Burr ML, Sweetnam PM, Williams G, Welsby E, Hughes SJ, Renton R. A randomised controlled trial of acetyl salicylic acid in the secondary prevention of mortality from myocardial infarction. BMJ 1974; i: 436-440.
  5. Dixon B. The 'top 50'; a perspective on the BMJ drawn from the Science Citation Index. BMJ 1990; 301: 747-751.

Former studies

Name of studyDates
Respiratory surveys (Rhondda, Leigh Lancashire, Annandale, Vale of Glamorgan, Staveley) including first ECG surveys. 1954 - 1958
Blood Pressure surveys (Rhondda and Vale of Glamorgan) 1954 - 1956
Glaucoma surveys 1963 - 1965
Studies of industrial workers (Flax workers, asbestos workers, steel workers, slate workers) ~1964
Studies of iron deficiency anaemia (observational studies and intervention studies) 1964 - 1969
Environmental lead studies 1968
Aspirin studies 1968
Studies of migraine ~1970
Nutrition of the elderly 1970
Magnesium and cardiovascular disease 1970
Barry-Caerphilly child growth study 1972 - 1979
Asthma studies 1973
School milk supplementation study 1976 - 1978
Caerphilly cohort study 1979
Diet and reinfarction trial (DART) 1983 - 1989

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Potential collaborators

An independent steering committee reviews all requests for collaboration.

Read more about collaborating

Phase variables

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