A proposed trial of heart disease prevention in industry

Serum triglycerides are a risk factor for myocardial infarction but not for angina pectoris. Results from a 10-year follow-up of Uppsala primary preventive study

At a follow-up 7-10 years after a health survey of men born in 1920-1924 in the municipality of Uppsala, 31 of the participants (n = 2322) had died from ischaemic heart disease (IHD). In response to a letter to all men alive in 1980, 106 men declared that they had had a myocardial infarction (MI) (verified or suspected). In 58 cases MI was verified from the hospital records. 28 other men had had typical central chest pain (angina pectoris) only. In another 20 men other diagnoses explained the chest pain for which they were treated in hospital. The health screening values for S-cholesterol and S-triglycerides, blood pressure and smoking habits were analysed in relation to the occurrence of IHD. In this prospective study, smoking, hypertension, S-cholesterol and S-triglycerides were identified as risk factors for fatal and non-fatal MI. The risk factor values were similar in subjects suffering from angina pectoris only to those in subjects who also developed ECG and/or transferase changes, with the exception of S-triglyceride concentration, which was normal in the group with angina pectoris. The subjects who had a fatal MI had a significantly higher blood pressure than those with non-fatal MIs, but otherwise these two groups did not differ. The results emphasize the importance of scrutinizing questionnaire data with regard to chest pain and of selection of end-points when risk factor patterns are described for cardiovascular diseases.

Risk factors for coronary heart disease in perspective. European intervention trials

High blood pressure, smoking, and lipid abnormalities are the dominating risk factors for myocardial infarction and sudden coronary death. The influence of one risk factor is markedly modified by other risk factors. In countries with low cholesterol levels, myocardial infarction and sudden coronary death may be uncommon, whereas stroke becomes a relatively important sequelae in patients with severe hypertension. However, in most western countries myocardial infarction and sudden coronary death are more common than stroke, especially in patients with moderate blood pressure elevations. The results of intervention studies in coronary heart disease must be viewed in the light of the general risk factor pattern. The side effects of drugs should be considered since large-scale intervention is often required in order to save a relatively small number of lives. In those at high risk from cardiovascular complications, certain drugs are possibly more effective than others in preventing the more serious end points. The results of the Oslo trial are compared with those of the WHO Multifactorial Trial, which randomized factories to intervention and control (nonintervention) in England, Belgium, and Italy, and also with the Göteborg Multiple Risk Factor Intervention Trial. A comparison of the different trials might indicate caution with respect to drug treatment in people with moderately increased risk factors. The effect of the incidence of coronary heart disease in different trials correlated broadly with changes in risk factors. Varying effects on mortality and morbidity might be found for different treatment modalities.

Belgian heart disease prevention project: incidence and mortality results

Results are presented from the Belgian Heart Disease Prevention Project, part of the WHO European Collaborative Trial in the Multifactorial Prevention of Coronary Heart Disease (CHD). 19 409 men aged 40-59 yr took part; they were employed in thirty factories which formed the allocation units for a randomised controlled trial lasting 5-6 yr. The intervention package consisted largely of health education promoting a cholesterol-lowering diet, smoking cessation, weight control, physical activity, and treatment of arterial hypertension. A programme of information was supplemented by face-to-face counselling at the workplace by two physicians attached to the project. The coronary risk profile was reduced in the intervention group, compared with that in the control group, especially during the first 4 yr, by effects on serum cholesterol, number of cigarettes smoked daily, and arterial blood-pressure. Total mortality was 17.5% lower in the intervention group than in the control group (p = 0.038). Coronary mortality was reduced by a non-significant 20.8% whereas CHD incidence (non-fatal myocardial infarction plus fatal myocardial infarction plus sudden deaths) was reduced by 24.5% (p = 0.031). Non-fatal myocardial infarction (not a major end-point) was similarly reduced by 26.1% (p = 0.030).

UK heart disease prevention project: incidence and mortality results

Results are presented for the UK centre of the WHO European Collaborative Trial in the Multifactorial Prevention of Coronary Heart Disease (CHD). 18 210 men took part, aged 40 to 59; they were employed in 24 factories, which formed the allocation units for a randomised controlled trial lasting 5-6 years. Intervention comprised advice on cholesterol-lowering diet, smoking cessation, weight control, exercise, and treatment of hypertension. Advice was given mainly through factory medical departments, the staff being supplemented a little by a visiting central team. Self-reported cigarette smoking was moderately reduced, but changes in other risk factors were small and not well sustained. There was no clear effect on hard CHD end-points (coronary deaths and myocardial infarction) or on all-causes mortality. However, there was a 36% reduction in the rate at which intervention subjects reported ill with other CHD (principally angina) during the study, and at the end fewer intervention men gave positive responses to a self-administered questionnaire on angina and chest pain. These apparent benefits were not substantiated by electrocardiographic evidence, suggesting that participation in a heart disease prevention campaign may bias reporting of symptoms. Experience in other centres of the Collaborative Trial, however, suggests that more effective risk factor control does reduce CHD incidence and mortality. This implies that for the UK the problem is to find means of enhancing the acceptance of health advice.

Heart disease prevention project: a randomised controlled trial in industry

Twenty-four factories or other occupational groups, employing 18 210 men aged 40 to 59, were formed into matched pairs. One of each pair was allocated randomly to receive a five to six year programme of medical examinations and intervention to reduce the levels of the main coronary risk factors. Men at factories in the intervention group were given advice on dietary reduction of plasma cholesterol concentrations, stopping or reducing cigarette smoking, regular exercies for the sedentary and reduced energy intake for the overweight, and hypertension was treated. The programme was delivered mainly through existing occupational medical services, helped by a small central staff. Personal consultations were largely confined to men with a high risk of developing coronary heart disease. Changes in risk factors were assessed by regular standardised examinations of random samples of men. The spread of information by general propaganda proved easy, but a change in habits seemed to require personal contact. Small but significant reductions occurred, mainly in the high-risk group, but these were not sustained when pressure was relaxed.

Predictability of sudden death from resting electrocardiogram. Effect of previous manifestations of coronary heart disease

The sudden death rate from coronary heart disease over a mean period of 4 years was related to the electrocardiographic findings in 3 groups of subjects, survivors of myocardial infarction, employed men, and employed men with no symptoms or history of coronary disease. Within each group the sudden death rate correlated with the number of electrocardiographic findings, particularly Q, ST, and T wave items. However, between groups there were large differences in sudden death rates in subjects with the same findings. These were greatest in the case of ventricular conduction disturbances and disturbances of rhythm and rate which appeared to be benign in those free of symptoms but ominous after infarction. Findings predictive of sudden death were also predictive of non-sudden coronary deaths. It is concluded that the electrocardiogram is only one of several aids to the diagnosis and assessment of severity of disease and not a substitute. Prognoses derived from clinical case series are inappropriate to symptomless individuals in whom isolated electrocardiographic findings denote little increase in risk.