Subjects and methods

The British regional heart study is a prospective study of cardiovascular disease involving 7735 men aged 40–59 years selected from the age–sex registers of a single group general practice in each of 24 towns in England, Wales, and Scotland and examined from January 1978 to July 1980. Men with pre-existing cardiovascular disease or receiving regular medical treatment were not excluded and the overall response rate was 78%. The criteria for selecting the town, the general practice, and the subjects as well as the methods of data collection have been reported previously.19 Research nurses administered to each man a standard questionnaire (Q1), which included questions on smoking habits, alcohol intake, and medical history. Several physical measurements were made and blood samples (non-fasting) were taken for measurement of biochemical and haematological variables. Five years after the initial examination (1983 to 1985), a postal questionnaire (Q5) similar to the one administered at screening was sent to all surviving men; detailed information on medical history, and changes in smoking and drinking behaviour, and in other risk factors, was obtained from 98% (n = 7275).

Results

During the mean follow up period of 12.8 years from the fifth year questionnaire in the 655 men with history of CHD, there were 294 deaths from all causes (46.1/1000 person years), of which 208 were attributed to cardiovascular causes (32.7/1000 person years) mainly caused by CHD (175 deaths; 27.5/1000 person years).

Discussion

While there is some evidence from clinical studies to suggest that heavy drinking is harmful in subjects with coronary artery disease,17 the effect of light to moderate drinking in such subjects has not been clearly established. The clinical studies suggest that alcohol may aggravate angina and that even low to moderate doses may impair left ventricular performance in patients with recent or old myocardial infarction.17 ,29 ,30 In our study involving middle aged and older men with established CHD, light alcohol intake (1–15 units per week) was not associated with any significant effect, deleterious or beneficial, compared to occasional drinkers (< 1 unit per week) or lifelong teetotallers. There is an indication that higher levels (⩾ 3 drinks per day) may be harmful in those men with a history of previous myocardial infarction, which supports the findings of the clinical studies.17 This adverse effect at higher levels was seen even if heavy drinkers (> 6 drinks per day on a daily basis; > 42 units per week) were excluded. Some of those classified as light drinkers at Q5 might have been heavier drinkers in the past. This might have increased the risk of mortality in those classified as light drinkers. However, the confirmation in this study of the benefits of light to moderate drinking on CHD mortality in men with no diagnosis of CHD supports the validity of the findings in men with the diagnosis of CHD.

The effects of alcohol on subsequent risk of CHD has seldom been assessed in men with established CHD. Several prospective studies into alcohol related outcomes have examined the effects of alcohol in men with and without pre-existing disease (variously defined) and in most of these a U shaped or inverse relation has been observed between alcohol intake and outcome.10-16 In the recent US cancer prevention II study involving 490 000 men and women, using non-drinkers as the baseline, regular drinking was associated with a greater reduction in CHD mortality in those with cardiovascular related conditions, which included CHD, stroke, diabetes, and hypertension.15 These high risk subjects constituted one third of all subjects and contributed three quarters of all cardiovascular deaths. The reduction in risk was seen in those drinking less than daily but at least three times a week and was similar at all levels of alcohol intake—that is, there was no dose–response effect. It was suggested that alcohol may confer greater benefit on those at high risk of cardiovascular disease. This study did not examine specifically the outcome in men with established CHD (definite myocardial infarction or angina), who are at much higher risk of death than men with hypertension or diabetes. In our study, when we examined the effect of alcohol on CHD mortality in men with and without cardiovascular related conditions using similar criteria, the same pattern emerged in that the reduction in CHD mortality was greater in those with cardiovascular related conditions than in those without. However, when our analysis is restricted to men with established CHD no benefit is evident.

In contrast to our study, the recent US physicians health study showed that “men with a history of myocardial infarction with light to moderate intake of alcohol have a slight but clinically important decrease in total mortality compared with those who never or rarely drink alcohol”.18 In that baseline group of never/rarely drinkers at the time of inquiry, no distinction was made between lifelong teetotallers and ex-drinkers. In men aged 40–84 years usually drinking 2–6 drinks per week, total mortality was decreased by 28%, cardiovascular mortality by 24%, and non-cardiovascular mortality by 39% after adjustment for age, smoking, diabetes, physical activity, and BMI. The subjects were elderly (69% were over 65 years old) and no account was taken of ill health or medication which might have led to reduction in alcohol intake other than for recall of hypercholesterolaemia or hypertension. The average intake in these high social class subjects was low and there were very few heavy drinkers in whom to examine the effects of heavier drinking (⩾ 3 drinks per day) on mortality.

Critical to the comparison of the present study with previous studies is the issue of the baseline group used. In the physician health study, current non-drinkers constitute the baseline and we have shown that this mixed group of lifelong teetotallers and ex-drinkers is not appropriate for the evaluation of the effects of alcohol on cardiovascular or all cause mortality.8 ,23 ,24 There is little doubt that ex-drinkers have characteristics which greatly increase their mortality risk and they almost always have the highest mortality rates of any of the alcohol categories. Combining ex-drinkers and lifelong teetotallers, groups which vary in their proportions in different populations, can only lead to a base group with characteristics which cannot be adequately taken into account by adjustment procedures and which increase the risk of mortality.

In our present study, ex-drinkers had the highest risk of cardiovascular and all cause mortality compared to other groups, while lifelong teetotallers had a similar risk to occasional drinkers. Although light drinkers showed the lowest risk, the difference was very small compared to occasional drinkers. If the physician health study had used occasional drinkers (1–4 drinks per month) as their baseline comparison group, the reduction in total mortality in men with a previous myocardial infarction on 2–6 drinks per week would be 15%, for cardiovascular mortality the reduction would be 18%, and for non-cardiovascular mortality it would be 5%, none of which would be significantly different from baseline. If we had restricted the analyses to men with definite myocardial infarction and used all non-drinkers (lifelong teetotallers and ex-drinkers combined) as the comparison group, our results would be similar to those of the physicians health study, with both occasional drinkers (1–2 per month) and light drinkers showing lower mortality rates than non-drinkers. Our data suggest that the magnitude of benefit associated with light drinking (2–6 drinks per week) in the physicians health study has been exaggerated by the use of an inappropriate comparison group.

In our study, moderate/heavy drinking in men with a history of previous myocardial infarction is associated with a marginally significant increase in risk of cardiovascular death and a significant increase in all cause mortality. In the men with angina only and no history of myocardial infarction, albeit a very small group, there appears to be no adverse effect from moderate/heavy drinking. These findings may reflect the direct effect of alcohol on the damaged heart muscle of those with definite myocardial infarction, and may justify the comment that “in patients with pre-existing cardiovascular disease the use of alcohol is contraindicated, particularly where ventricular function is impaired”.31 Our data suggest that light drinking may not be contraindicated but that moderate/heavy drinking may increase risk. In our moderate/heavy group, 84% were moderate drinkers with an intake of 16–42 UK units per week.

By contrast with the effects of alcohol, smoking cessation in men with established CHD was associated with a reduction in death from CHD, cardiovascular disease, and all causes, and for cardiovascular mortality the reduction was significant. Those who continued to smoke showed over a twofold increase in risk compared with those who had never smoked. Long term ex-smokers (who had given up for more than five years before the start of the follow up period) showed risk levels comparable to those of never smokers. Using the relative risks calculated in the cancer prevention II study, the authors have estimated the probability of death from any cause in the general US population aged 35–69 years.15 In both men and women, in drinkers and non-drinkers, smoking doubled the risk of death compared with non-smoking. The risk of death was slightly less in drinkers than non-drinkers; about 16% less in non-smokers and 6% less in smokers. They conclude that “the benefits of moderate alcohol consumption (1–2 drinks per day) are much smaller than the hazards of tobacco use”.15

Conclusion

When an appropriate baseline group—that is, occasional drinkers—is used, regular light alcohol consumption (1–14 UK units per week) in men with established CHD is not associated with any significant benefit or deleterious effect for CHD, cardiovascular mortality, or all cause mortality. Higher levels of intake (⩾ 3 drinks per day) are associated with increased mortality in men with previous myocardial infarction. By contrast, giving up smoking in men with established CHD halves the risk of mortality. Given the high absolute rate of death in men with established CHD, the absolute benefit of giving up smoking in men surviving a myocardial infarction is substantial. Time would be better spent assisting such men to stop smoking than trying to encourage the lifelong teetotallers or ex-drinkers among them to drink.