COMMUNITY SCREENING FOR CORONARY HEART DISEASE RISK FACTORS Results of screening in 10,000 adult males Anne Cruess-Callaghan, N. Hickey, R. Mulcahy, G. F. Gearty and G. J. Bourke From the Research and Information Committee of the Irish Heart Foundation, 4 Clyde Road, Dublin 4.
Summary A FEASIBILITY study of primary prevention of coronary heart disease in IreJand is described. The results of screening 10,000 adult males for coronary heart disease risk factors are reported. Eighty three per cent of the population screened were less than 55 years of age and 86.6 per cent were apparently healthy subjects. Nearly 10 per cent were classified in the "overt" disease category, 16 per cent were classified as high risk and only 15.2 per cent were free from all the acknowledged habits and characteristics associated with CHD.
Introduction There is a high morbidity and mortality from coronary heart disease (CHD) in Ireland as in other Western countries. Mortality occurs mainly in the acute stage before medical attention can be provided (Yater et ah, 1948; Stamler, 1963; McNeilly and Pemberton, 1968). Sidel et ah (1969) have stressed the fact that, even allowing for every modern facility for acute coronary care, the total mortality from CHD is unlikely to be reduced by more than 10 per cent with present methods of treatment. Epidemiological studies have identified certain habits and attributes which are associated with increased risk of CHD. (Kagan et al., 1963; Paul et al., 1963; Borhani et ah, 1963; Keys et al., 1963; Stamler et al., 1968). Acknowledged major risk factors are hypertension, hypercholesterolaemia Pnd cigarette smoking. Other well documented risk factors include obesity, physical inactivity and diabetes mellitus. Reduction or elimination of major risk factors may offer a real possibility of decreasing the incidence of CHD through primary prevention. The purpose of this paper is to describe a feasibility study of primary prevention at a national level. This study was commenced by The Irish Heart Foundation in 1968. The aims of the MEDISCAN project are : 1. To develop an economical, efficient and acceptable method of risk factor screening which is applicable to the general population. 2. To identify those individuals in the community who are susceptible to CHD. 3. To refer high risk cases to practitioners and physicians, and to involve the medical profession in the primary prevention of CHD.
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COMMUNITY SCREENING FOR CORONARY HEART DISEASE RISK FACTORS
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4. To assess the Iongterm effect of the programme on the subject's risk factor status. The present report deals with the first two aims. A two year follow-up study is at present under way to examine the effect of medical intervention.
Material and Methods 10,000 self-selected male volunteers in the 25-70 years age group were screened in the MEDISCAN community screening programme. The sample, taken from a large and varied cross-section of the Irish population, was drawn from cities and towns (54 per cent) and from industrial areas (46 per cent) throughout the entire country. Screening was carried out in mobile units each staffed by two nurses specially trained in epidemiological techniques. Each unit consists of two examining rooms, a waiting area and a small laboratory space. Screening takes approximately 20 minutes per person. The procedure consists of a short questionnaire, measurement of height, weight, biacromial diameter and skinfold thickness; electrocardiogram, blood pressure estimation, serum cholesterol and urinalysis. The programme, including the printing out of an appropriate letter to each subject and to his doctor, is computerised at the Computer Laboratory, Trinity College, Dublin. Details of organisation and methodology (Hickey et al., 1971), and of data processing (Moriarty, 1970) have already been published.
Procedure Screening is performed at local community level and in industry. Only males over the age of 25 years are eligible. Individuals in the 30-59 years age group are of particular importance but screening is not refused to those outside this age group. Prior to screening, the cooperation and the participation of local medical practitioners and industrial medical officers are sought. Appointments fcr screening are arranged at a convenient local centre two to three weeks before screening takes place. Each subject is given an appointment card and a plastic container with instructions to bring a freshly-voided urine specimen. Approximately four weeks following screening each subject receives a letter advising him that he should return to his doctor or that no evidence of heart disease nor of medical conditions predisposing to it were.found. In appropriate cases advice is given to stop smoking, to reduce weight and to take more exercise. Only those who are classified high risk or "overt" disease are referred for medical attention. Complete details of screening are sent to the doctor nominated by the subject.
Risk Categorles Five risk categories are defined (Table I). "Overt" disease includes those with a positive angina questionnaire and/or those who have an abnormal electrocardiogram. The difference between the high risk and the moderate risk groups is based on arbitrary levels of diastolic blood pressure and of serum cholesterol. The term non-medical risk is applied to those who smoke five cigarettes or more daily, and/or those who are classed as
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doing minimal activity both on-job and off-job and/or those who are 15 per cent or more above their desirable weight. Each individual is placed in the highest risk category for which he qualifies. TABLE I Risk category criteria.
"Overt":
Positive angina questionnaire + / - -
abnormal ECG.
High :
Diastolic blood pressure 110 mmHg or over + / - mgm/100 ml or more + / - - glucosuria.
Moderate :
Diastolic blood pressure 95-109 mmHg + / - mgm/100 ml.
Non-Medical:
Cigarette smoker + / - -
serum cholesterol 275
serum cholesterol 230-274
relative overweight + 15 per cent or more + / -
physical inactivity. Low :
Absence of above criteria.
Results Details of the first successive 10,000 screenings are reported. The age distribution of the sample screened and the data concerning previous history of diseases of the cardiovascular system are shown in Table II. Of those screened 83 per cent were less than 55 years and 13.4 per cent had a previous history of heart disease, hypertension, diabetes or stroke. TABLE II Age distribution and previous history* of 10,000 subjects screened.
Age group
< 35 yrs.
Number
Per cent
1,891
18.9
Per cent with previous history of disease 3.2
35-44
3,527
35.3
7.4
45-54
2,893
28.9
16.0
55-64
1,503
15.0
32.5
186
1.9
35.0
10,000
100.0
65 + All ages
13.41
* Heart disease, hypertension, diabetes or stroke.
The distribution of the subjects into risk categories according to age groups is shown in Table Ill. This Table also shows the mean age of the subjects in each risk category. In all, 945 subjects (9.5 per cent) were classified as "overt" disease. Of these, 351 (3.5 per cent) had probable angina only, 508 (5 per cent)
COMMUNITY SCREENING FOR CORONARY HEART DISEASE RISK FACTORS
241
had abnormal items in the electrocardiogram only, and 86 subjects (0.9 per cent) had both a positive angina questionnaire and an abnormal electrocardiogram. TABLE III Risk categories of 10,000 males distributed ito 10 year age groups.
"Overt"
Age group
Pos. Ang. only
9< 3 5
38
35-44
Abn. ECG only
High
Mod
Non -Med.
Low
Total
2
51
168
577
604
451
1891
82
6
109
576
1259
938
557
3527
45-54
105
26
163
559
1146
560
334
2893
55-64
111
41
159
269
492
277
154
1503
15
11
26
30
53
27
24
186
351
86
508
1602
3527
2406
1520
10000
16.02
35.27
24.06
15.20
100
45.8
44.3
41.8
41.1
44.0
65+ Total %
Mean Age Yrs.
Pos. Ang. + Abn. ECG
9.45
49.7
Sixty nine per cent of the abnormal ECGs were classified as "ischaemic" using the Minnesota Code. The term "ischaemic" is used for such abnormalities as are indicated in Table IV. In 59 per cent of the subjects with abnormal ECGs there was no previous history of heart disease. 1,602 subjects (16.0 per cent) were classified as high hisk, and 3,527 subjects (35.3 per cent) as moderate risk. In 2,406 subjects (24.1 per cent) cigarette smoking, overweight and lack of physical activity were present either singly or in combination. 1,520 subjects (15.2 per cent) were free from all the above risk factors. The mean age in the "overt" risk category was 49.7 years compared to 41.1 years in the low risk group. As expected the percentage of low risk individuals is highest (23.3 per cent) in the less than 35 years age group and lowest (10.5 per cent) in the over 55 year age groups. The most marked association with ~age was in the "overt" disease group. 4.8 per cent of subjects in the 25-34 year age groups had "overt" disease, whilst 21.4 per cent of subjects in the over-55 years age groups had "overt" disease.
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IRISH JOURNAL OF MEDICAL SCIENCE TABLE IV 594 ECGs showing classifiable MinnesodaCode items, distributed into ischaemic and other categories. Minnesota Code * Ventricular conduction defects
Total 96
QRS axis deviation
18
High amplitude R waves
32
* S-T junction (J) and segment depression * T wave items * A-V conduction defects * Q & QS patterns
52 176 4 80
Arrhythmias
136
Total
594
* = Ischaemic. Discussion
There is insufficient evidenc3 to support the concept that reduction of risk factors at a community level will lead to a reduction in the incidence of coronary heart disease, although our knowledge of CHD risk factors, derived from epidemiological and other studies, would suggest the logic of such ~n approach. Results which are obtained under hospital and laboratory conditions do not necessarily apply to the community at large. While there is some evidence that dietary control of hypercholesterolaemia may reduce morbidity and mortality from CHD in a primary prevention programme (Miettinen et al., 1972; Dayton et al., 1968; Christakis et al., 1966), results from studies of multiple risk factor alteration are not yet available to guide us. The present report outlines a programme of coronary risk factor identification in a family doctor setting and in industry. One outstanding feature has be~n the widespread public enthusiasm with which screening is accepted. In 98 per cent of the one or two-week screening programmes maximum turnover was recorded. Eighty seven per cent of those screened were apparently healthy males and 83 per cent were under the age of 55 years. Screening programmes can, therefore, attract young healthy males in adequate nurhbers. A follow-up study of progress should determine the extent to which such people respond to screening and to medical advice. The incidence of CHD in communities is difficult to estimate and is very variable. Prevalence data from the United States as a whole were derived from the National Health Survey carried out by the U.S. Public Health Service in 1960. A national sample of 6,672 males and females aged 18-79
COMMUNITY SCREENING FOR CORONARY HEART DISEASE RISK FACTORS
243
years were examined. The prevalenca of CHD (both angina and myocardial infarction) in males aged 25-34 years was 4 per 1,000 and in the 65-74 year age group was 116 per 1,000. Intermediate age groups showed an increasing prevalence with age. Results from Framingham (Dawber et al., 1957), Albany (Doyle et al., 1959), Chicago (Stamler et al., 1960) and Tecumseh (Epstein et al., 1965) show that similar prevalence rates are found amongst different communities within the same country. Rose (1962) noted that two per cent of 1,848 English manual workers aged 35-59 had definite ECG changes in the absence of symptoms and a further ten per cent had less definite ST depression or T-wave changes. Four per cent of his men between 35-59 years had symptoms of angine pectoris (Rose, 1966). The occurrence of probable or possible CHD in this Irish survey, using the same protocol as Rose (1962) was 9.5 per cent. Among men in the 35-64 year age groups the occurrence of CHD was 10.1 per cent. The frequency of angina pectoris was 4.4 per cent for all ages and 4.6 per cent for men aged 35-64 years. These figures are very similar to those recorded in England by Rose (1962). Whilst the desirability of detecting cases of angina pectoris in the population may be questioned because of our unproven ability to treat them adequately, it is possible that risk factor alteration may lead to symptomatic improvement, or may prevent sudden death or acute myocardial infarction in a proportion of these cases. 1,602 (16 per cent) of subjects were classified high risk on the basis of hypercholesterolaemia and/or hypertension and/or glycosuria. The mean age of subjects in this group was 45.8 years. In the majority of these subjects hypertension and hypercholesterolaemia were symptomless and occult. Screening procedures may, therefore, be essential if adequate treatment of risk factors at a population level is to be achieved. In the case of other risk factors, such as smoking, overweight and physical inactivity, educational programmes may acquaint people of the dangers associated with these factors. However, it remains to be seen whether a primary prevention programme, such as MEDISCAN, can, by its personal approach, be o f greater value in altering such risk factors as cigarette smoking than broadly aimed educational programmes. In the MEDISCAN programme only the "overt" and high risk factor groups were referred to their family doctor. The arbitrary cut-off points used to include subjects in these high risk groups are not ideal. The system ignores the evidence that multiple risk factors such as smoking, obesity, moderate hypertension and cholesterol elevation in various combinations may be even more dangerous than single strongly positive major risk factors. Nevertheless, for practical reasons, screening procedures must have cut-off points. At ~ present the possibility of devising a scoring system is being examined in an attempt to quantify risk status in a more satisfactory manner. More than eight out of ten of our subjects had one or more risk factors and should therefore be referred for attention in a primary prevention
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programme. However, allowing for the limited facilities presently available in health services, and the emphasis among practising doctors on therapeutic rather than preventive medicine, those at greatest risk should receive priority in a primary prevention scheme. The male volunteers screened represent that segment of our community which is most likely to benefit from a primary prevention programme. Modern society's exposure to environmental risk factors ensures that almost every population group is fertile soil for prevention. Prevention offers the most practical and realistic approach and is the one which the Irish comm-mity would appear to endorse. To what extent, however, will the at-risk groups seek and respond to medical advise? To what extent will the medical profession participate in primary preventive measures ? These are questions which are at present being studied. References Borhani, N. O., Hechter, H. H. and Breslow, L. 1963. Report of a ten-year follow-up study of the San Francisco longshoremen---Mortality from coronary heart disease and from all causes. J. chron. Dis. 16, 1251. Christakis, G., Rinzler, S. H., Archer, M., Winslow, G., Jampel, S., Stephenson, J., Friedman, G., Fein, H., Kraus, A. and James, G. 1966. The anti-coronary club : a dietary approach to the prevention of coronary heart disease. A seven year report. Amer. J. pub]. HIth. 56, 299. Dawber, T. R., Moore, F. E. and Mann, G. V. 1957. Coronary heart disease in the Framingham study. Amer. J. publ. Hlth. (Suppl. 4), 4, 4. Dayton, S., Pearce, M. L., Goldman, H., Harnish, A., Plotkin, D., Shickman, M., Winfield, M., Zager, A., Dixon, W. 1968. Controlled trial of a diet high in unsaturated fat for prevention of atherosclerotic complications. Lancet, ii, 1060. Doyle, J. T., Heslin, S. A., Hilleboe, H. E., Formal, P. F. and Korns, R. F. 1959. Early diagnosis of ischaemic heart disease. New Engl. J. Med. 261, 1096. Epstein, F. H., Ostrander, L. D., Johnson, B. C., Payne, M. W., Hayner, N. S., Keller, J. B. and Francis, T. 1965. Epidemiological studies of cardiovascular disease in a total community--Tecumseh, Michigan. Ann. intern. Med. 62, 1170. Heart Disease in Adults. 1964. U.S. 1960-62 Series I1. No. 6 U.S. Dept. of Health, Education and Welfare, Public Health Service, Washington. Hickey, N., Bourke, G. J., Gearty, G. and Mulcahy, R. 1971. MEDISCAN: A population screening programme for the detection of coronary heart disease risk factors. J. Irish med. Ass. 64, 155. Kagan, A., Kannel, W. B., Dawber, T. R. and Revotskie, V. N. 1963. The coronary profile. Ann. N.Y. Acad. Sci. 97, 883. Keys, A., Taylor, H. K., Blackburn, H., Brozek, J., Anderson, J. J. and Simonson, E. 1963. Coronary heart disease amongst Minnesota business and professional men followed fifteen years. Circulation, 28, 381. McNeilly, R. H., Pemberton, J. 1968. Duration of last attack in 998 fatal cases of coronary disease and its relation to possible cardiac resuscitation. Brit. mad. J. iii, 139. Miettinen, M., Turpeinen, O., Karvonen, M. J., Elosuo, R. and Paavilainen, E. 1972. Effect of cholesterol-lowering diet on mortality from coronary heart disease and other causes. Lancet, ii, 835. Moriarty, J. J. 1970. MEDISCAN data processing system. Computer Bulletin, 14, 222. Paul, O., LePper, M. H., Phelan, W. H., Dupertuis, G. W., MacMillan, A., McKean, H. and Park, H. 1963. A longitudinal study of coronary heart disease. Circulation, 28, 20. Rose, G. A. 1962. The diagnosis of ischaemic heart pain and intermittent claudication in field surveys. Bull. WId. Hlth. Org. 27, 645. Rose, G. A. 1968. Principles and practice of screening for disease. J. M. G. Wilson and G. Junger. W.H.O. Public Health Pap. INo. 34, Geneva, p. 89.
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Sidel, V. W., Acton, J. and Lown, B. 1969. Models for the evaluation of pre-hospital coronary care. Amer. J. Cardiol. 24, 674. Stamler, J., Lindberg, H. A., Berkson, D. M., Shaffer, A., Miller, W. and Poindexter, A. 1960. Prevalence and incidence of coronary heart disease in Strata of the labour force of a Chicago industrial corporation. J. chron. Dis. 11, 405. Stamler, J. 1963. Are heart attacks preventable ? Illinois Med. J. 123, 145. Stamler, J., Berkson, D. M, Monjonnier, L., Lindberg, H. A., Hall, Y., Levinson, M., Burkey, F., Miller, W. A., Epstein, M. B. and Andelman, S. L. 1968. Epidemiological studies on atherosclerotic coronary heart disease: causative factors and consequent preventive approaches. Prog. Biochem. Pharmacol. 4, 30. Yater, W. M., Traum, A. H., Brown, W. G., Fitzgerald, R. P., Geisler, M. A. and Wilcox, B. B. 1948. Coronary artery disease in men eighteen to thirty nine years of age. Report o~ eight hundred sixty six cases, four hundred fifty with necropsy examinations. Amer. Heart J. 36, 334, 481, 683.