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UNK-BEL: Belfast/PRIME Study Contributors from the MPC: Angela Scott, Evelyn Gardner and John Yarnell

© National Institute for Health and Welfare and the MORGAM Project investigators Last updated: 18 December 2008 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: 34 - PRIME/Belfast
  • Administrative centre: Department of Epidemiology & Public Health, The Queen's University of Belfast, Northern Ireland, UK
  • Key personnel: Frank Kee (Principal Investigator), Alun Evans (former Principal Investigator), John Yarnell, Angela Scott, Evelyn Gardner
• RUs:
  • 01: Belfast. Belfast, Castlereagh, North-Down, and Ards Health Districts in east of Northern Ireland. The area is 60% urban with declining heavy industries and textiles. The population is characterized by increasingly high unemployment and high cardiovascular disease mortality.
• RUAs:
  • UNK-BELa
• Cohorts:
  • Cohort 21: 49-60 years old men from the RU who were examined in the baseline survey in 1991-1994.

Cohort recruitment and the baseline examination

The target was to recruit 2500 men aged 50-59 years. The cohort was recruited to broadly match the social class structure of the background population. The recruitment was based firstly on industry and various employment groups, excluding those with more than 10% of their workforce of foreign origin. Secondly the recruitment was based on general practice. This provided the opportunity to recruit unemployed and retired persons to the cohort. 5266 men were contacted through industry, the civil service and general practice by letter stating the aim of the study and asking to agree to an annual follow-up. 2745 (i.e. 52%) of them agreed to participate. The size of the cohort is 2745 men.

The baseline examinations were carried out in 1991-1994. The PRIME baseline procedures are described in reference [1].

DNA are available for the members of the Cohort.

End-points followed up

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

End of follow-up period

• Fatal events:
  • Five years after the date of examination of each person
  • In year 2008 the follow-up was extended to 10 years from the baseline examination for each person
• Non-fatal events:
  • Five years after the date of examination of each person
  • In year 2008 the follow-up was extended to 10 years from the baseline examination for each person

Follow-up procedures

Sources of data

• Person himself
• Relatives
• General practitioner, specialist or occupational medicine department
• Registrar General's data: The responsibilities of the General Register Office, lead by the Registrar General, includes the administration of registration of deaths through the 26 District Registration Offices of Northern Ireland. Death certificates of deaths in Northern Ireland were obtained from the General Register Office.
• Central Services Agency (CSA)

Procedure

CSA informed the MPC when any of the PRIME subjects died, moved to a health authority in Great Britain or moved outside Northern Ireland.

Each year, on the anniversary of the initial examination, each subject was followed-up by means of a questionnaire sent to his home. Some of the answers to this questionnaire lead to further enquiry.

The procedure for contacting the subjects was:

1. Mail an Annual Follow-up Questionnaire, the letter of introduction and a stamped pre-addressed envelope, on the anniversary of the initial PRIME examination.
2. If there is no answer try to make contact by telephone.
3. If all this fails, contact:
   • his doctor(s) (general practitioner and/or specialist)
   • his Occupational Medicine Department
4. If this is unsuccessful make a home visit and, if necessary, talk to neighbours.
5. If no answer is obtained, search the Registrar General's data to verify that he is still alive.
6. If the person is alive, classify him as "lost to follow-up".
7. After 10 years try to establish if the subject is alive or dead by:
   • searching the Registrar General's data
   • reviewing the CSA reports

Whenever there was suspicion of an event, clinical information was sought directly from the hospital or general practitioner notes. All details of electrocardiograms, hospital admissions, enzymes, surgical operations, angioplasty, treatment etc. were collected. Death certificates were checked for supporting clinical and post-mortem information on cause of death. Whenever necessary, the circumstances of death were obtained from the practitioner or the family.

Diagnostic procedures

At baseline:

• History of MI
  • Documented: data not available
  • Self-reported:  An affirmative answer for the question "Have you ever been told by a doctor that you have had a myocardial infarction (heart attack)?" was considered as self-reported history of MI.
  • ECG: Persons with Minnesota code 1 is 1-1 or 1-2 (except 1-2-6) 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: An affirmative answer for either or both of following questions: "Have you ever had a dilatation or unblocking of one or more coronary arteries (angioplasty)?" and "Have you ever had coronary artery surgery (by-pass, etc...)?" was considered as self-reported history of cardiac revascularization.
• History of angina pectoris:
  • Documented: data not available
  • Rose questionnaire: As specified in item HISAP2 of MORGAM Form 21, but omitting Questions 6 and 7.
  • Self-reported: An affirmative answer to the question "Have you ever been told by a doctor that you have had angina?" was considered as self-reported history of angina pectoris.
• History of coronary heart disease, type unspecified: An affirmative answer to the question "Have you ever had other type of coronary heart disease?" was considered as history of coronary heart disease, type unspecified.
• History of stroke:
  • Documented: data not available
  • Self-reported: An affirmative answer to an option "Carotid arteries or arteries of the neck" under the question "Have you had any arterial disease involving the following arteries? was considered as self-reported history of stroke.
• History of Diabetes: An affirmative answer to the question "Have you ever been told by a doctor that you had diabetes or threatened diabetes?" was considered as history of diabetes.

During follow-up:

• Deaths: The PRIME "Deaths" Medical Committee assigned the underlying cause of death using all available information from the death certificate, from the autopsy report and from the general practitioner's, hospital and emergency team's notes. The code was used for the item DEATHDU of MORGAM Form 25. The causes of death from the death certificate were used for the items DEATHDA, DEATHDB and DEATHDC of MORGAM Form 25.
• CHD events: The PRIME Medical Committee independently classified the suspect coronary events using all medical information (see Follow-up procedures above). The MORGAM diagnostic category was derived from the PRIME classification according to the following table:

  PRIME classification	MORGAM DGNCAT
  Myocardial infarction was defined by one of the following sets of conditions: new diagnostic Q wave or other fresh typical electrocardiographic sign of necrosis; typical or atypical pain symptoms and new (or increased) ischaemia and myocardial enzyme levels higher than twice the upper limit; post-mortem evidence of fresh myocardial infarction or thrombosis.	1=definite MI
  Non sudden coronary death with: CHD symptoms; or history of CHD; or positive CHD findings at autopsy; and without evidence for another cause of death (clinically or at autopsy).	2=possible MI or coronary death
  Death occurring within one hour of symptoms with: CHD symptoms; or history of CHD; or positive CHD findings at autopsy; and without evidence for another cause of death (clinically or at autopsy).
  Unstable angina was defined as: a crescendo pain (change in frequency or severity of chest pain on exertion); or chest pain at rest; and angiographic stenosis over 50%; or a positive scintigraphy (if no angiographic data); or positive exercise stress test (if no angiographic or scintigraphic data); or electrocardiogram changes at rest (if no angiographic, scintigraphic or exercise stress test data); and no myocardial infarction; and no evidence of a non-coronary cause in the clinical history.	4=unstable angina pectoris
  Death occurring within one hour of symptoms with: no CHD symptoms; and no history of CHD; and no positive CHD findings at autopsy if any; and without evidence for another cause of death (clinically or at autopsy).	5=unclassifiable (fatal)
  Suspected coronary death with no other documentation or explanation: a death when a possible coronary cause is evoked during the complementary survey carried out by the local PRIME team but no CHD history nor documentation could be found.
  Unattended death. This corresponds to the definition of ICD-9 code 798.9.
  Death with suspicion of coronary cause which proved to be non coronary	7=no MI
  Pain only on effort (not at rest and not crescendo) and angiographic stenosis over 50%; or a positive scintigraphy (if no angiographic data); or positive exercise stress test (if no angiographic or scintigraphic data); or electrocardiogram changes at rest (if no angiographic, scintigraphic or exercise stress test data); and no myocardial infarction; and no evidence of a non-coronary cause in the clinical history.	8=irrelevant (EVTYPE=1)

  Coronary events occurring within 28 days of each other were considered as one event.

• Stroke events: The PRIME Medical Committee independently validated the suspect stroke events using all medical information (see Follow-up procedures above). For each  event where stroke could not be excluded, a PRIME code, specifying the subtype, as well as a three-digit ICD-9 code was given according to the MONICA protocol.

  Stroke events occurring within 28 days of each other were considered as one event.

References

1. Yarnell JW. The PRIME study: classical risk factors do not explain the several fold differences in risk of coronary heart disease between France and Northern Ireland. Prospective Epidemiological Study of Myocardial Infarction. Q J Med. 1998;91:667-76.

Updates to this document

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