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UNK-CAE: Caerphilly Contributor from the MPC: John Yarnell

© National Institute for Health and Welfare and the MORGAM Project investigators Last updated: 4 May 2006 For more information, please contact Kari Kuulasmaa (firstname.lastname@thl.fi)

Contents

• Cohort identification
• Cohort recruitment and the baseline examination
• End-points followed up
• End of follow-up period
• Follow-up procedures
• Diagnostic procedures
  • at baseline
  • during follow-up
• References
• Updates

Cohort identification

• Country: United Kingdom
• MPC: 72 - Caerphilly
  • Administrative centre: Department of Epidemiology and Public Health, The Queen's University of Belfast, Belfast
  • Key personnel: John Yarnell (Principal Investigator), Yoav Ben Shlomo, Evelyn Gardner
• RUs:
  • 01 - Caerphilly. It includes Caerphilly, a former mining town in South Wales, and outlying villages. The total population of the RU is about 40,000.
• RUAs:
  • UNK-CAEa
• Cohorts:
  • Cohort 21 - Participants of a re-examination of a survey of the whole male population of the RU aged 45-59. The baseline examination was carried out in 1984-88, when the age of the men was 47-67.

Cohort recruitment and the baseline examination

Electoral rolls for the defined area along with a private census conducted by the MPC's field workers, which supplied age by householders, were used to identify the men aged 45-59 years. Of the 2818 men initially identified, 2512 (89%) were seen in the initial survey in 1979-83. The participants of the initial survey were invited to a re-examination, which was conducted between 1984 and 1988. Cohort 21 includes the men seen at the re-examination, when their age was 47-67 years. In addition, a further 447 men, who had moved into the Caerphilly area, were recruited and added to the cohort. [1, 2]

The size of the MORGAM cohort and response rate to the 1984-1988 re-examination (using the eligible population 3118, obtained from a private census at that time, as the denominator) were:

DNA are available for the members of the Cohort.

End-points followed up

• Deaths: yes
• Non-fatal acute MI: yes
• Unstable angina pectoris: no
• Silent MI: no
• Cardiac revascularization: no
• Stable angina pectoris: no
• Non-fatal stroke events: yes
• Thromboembolic events: no

End of follow-up period

• Fatal events: 31 December 2000
• Non-fatal events: 31 December 2000

Follow-up procedures

Sources of data

• National Health Service (NHS) Registry: This is a central registry for persons registered with an NHS number to a general practitioner in England and Wales. Coverage should be 100% as very few persons are registered to private doctors without a NHS number. From the experience of the MPC, the coverage is 98-99% as they obtained some death certificates locally which had not been recorded by the central registry. The NHS Registry receives copies of the death certificates issued by the local registrar of births and deaths and the MPC receive a copies of these.
• Hospital Activity Analysis Lists: These are lists of hospital discharges with ICD coded diagnoses. The MPC included all possible hospitals in a 20 mile radius of Caerphilly to which patients may have been admitted.
• Hospital notes
• General practitioners' records
• Re-examination visits every 5 years: Re-examinations were carried out at approximately 5 year intervals and detailed questionnaires were obtained.
• Follow-up letter

Procedures

Mortality follow-up: The NHS numbers of the members of the Cohort were flagged at the NHS Registry, which recorded all deaths, also in Scotland and Northern Ireland.

Follow-up of non-fatal events:

• At the re-examination subjects were asked about all hospital admissions, particularly those for cardiovascular disease. Details concerning the date of admission, hospital and consultant were requested.
• Men who did not to attend for re-examination or who had left the study area were contacted by letter and asked to complete a similar follow-up questionnaire. The NHS Central Registry was used to trace subjects who had moved out of the area and who had re-registered with a new General Practitioner within the UK.
• Computerised data from Hospital Activity Analysis lists were used to provide an independent check on hospital admissions for coronary heart disease and stroke (ICD-9 codes 410-414.9 and 430-436 respectively) within the study area. Such admissions were linked to individual cohort members using dates of birth and address codes.

Diagnostic procedures

At baseline:

• History of MI:
  • Documented: data not available
  • Self-reported: An affirmative answer to an option "Heart attack or coronary thrombosis" under the question "Have you had any of the following illnesses in the last five years?" was considered as self-reported history of MI.
  • ECG: Person with Minnesota code 1-1 or 1-2 (except 1-2-6 and 1-2-8) in baseline ECG were considered having an ECG change indicating myocardial infarction.
  • Rose questionnaire: As specified in item HISMI4 of MORGAM Form 21.
• History of cardiac revascularisation:
  • Documented: data not available
  • Self-reported: data not available
• History of angina pectoris:
  • Documented: data not available
  • Rose questionnaire: As specified in item HISAP2 of MORGAM Form 21,
  • Self-reported: data not available
• History of coronary heart disease, type unspecified: data not available
• History of stroke:
  • Documented: data not available
  • Self-reported: An affirmative answer to an option "Stroke" under the question "Have you had any of the following illnesses in the last five years?" was considered as self-reported history of stroke.
• History of Diabetes: An affirmative answer to an option "Diabetes" under the question "Have you had any of the following illnesses in the last five years?" was considered as history of diabetes.

During follow-up:

• Deaths: Based on the death certificates, ICD-9 codes were assigned to the deaths in the MPC. Since about 1997, ICD-9 codes have been incorporated in the copy of the death certificates. The ICD codes were used for the relevant items of MORGAM Form 25.
• CHD events: For deaths found in the NHS Registry, the diagnostic classification was done using the ICD-9 codes of the underlying cause of death:

  ICD-9 code of the underlying cause of death	MORGAM DGNCAT
  410-414	3
  other	7

  This was done also even if the person had been hospitalized before the death. (Note that there were no deaths during follow-up with ICD-9 code 798 as the underlying cause of death.)

  For a non-fatal event, when the Re-examination questionnaire data suggested AMI, and/or the Hospital Activity Analysis List had ICD-9 code 410-414, the event was validated using hospital notes and a modification of the Old World Health Organization criteria (from the 1970s) [3]: ECG was not used. The event was coded as a definite non-fatal AMI if it had typical symptoms and enzymes twice above the normal limit. Other non-fatal events were considered as "no AMI", and they were not reported to MORGAM.

• Stroke events: For deaths found in the NHS Registry, the diagnostic classification was done using the ICD-codes of the underlying cause of death:

  ICD-9 code of the underlying cause of death	MORGAM DGNCAT
  430-431, 433-436	9
  other	4

  This was done also even if the person had been hospitalized before the death.

  For a non-fatal event, when the Re-examination questionnaire data suggested stroke, and/or the Hospital Activity Analysis List had ICD-9 code 430-438, the event was validated using Hospital notes and General Practitioners' records. The study committee for stroke classification used the available information to classify events as TIA, ischaemic stroke, haemorrhagic stroke, stroke of uncertain subtype, subarachnoid haemorrhage, or other vascular or non-vascular event. Stroke was defined as a focal or global neurological impairment of sudden onset, and lasting more than 24 h (or leading to death) and presumed vascular aetiology [2]. Cases of non-fatal subarachnoid haemorrhage were not reported to MORGAM.

References

1. Caerphilly and Speedwell collaborative heart disease studies. The Caerphilly and Speedwell Collaborative Group.J Epidemiol Community Health. 1984;38(3):259-62.
2. Greenwood R, McCarron P, Elwood P, Shlomo YB, Bayer A, Baker I, Frankel S, Ebrahim S, Murray L, Davey Smith G. The incidence and aetiology of stroke in the Caerphilly and Speedwell Collaborative Studies I: methods and incidence of events. Public Health. 2001;115(1):4-11.
3. Regional Office for Europe; World Health Organization. Myocardial Infarction Community Registers, Public Health Papers No. 5. Copenhagen: World Health Organization; 1977.

Updates to this document

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