Caerphilly Prospective Study

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.

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 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 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 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.

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 & 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.