Many factors make contribution to coronary disease

Press, 7 November 1978, Page 14

Many factors make contribution to coronary disease

Once again in your “Runners’ Diary” there is reference to marathon running giving “the best chance of immunity from coronary troubles”. There is no evidence that anything can provide immunity to this disorder whether it be diet, nonsmoking, normal blood pressure, or what have you.

Many factors contribute to coronary disease and it is unlikely that one form of intervention — for example, exercise —■ will give complete protection. Indeed the benefits of exercise may well be because the person who is active adopts other favourable behaviour patterns, such as the achievement of normal body weight, non-smoking, etc. It must be emphasised, however, that a substantial number of people suffer heart attacks who do not have any of the known coronary risk factors and there is much that we still have to learn about the causes and prevention.

The marathon immunity hypothesis has been around for some time and was fully discussed at a Marathon Symposium in New York in 1976. I have read the 1000-page proceedings of this meeting and my interpretation is that the majority view was that the hypothesis was unproven.

To prove the point scientifically would require that a healthy group of say 100 men and

women should be enlisted into a study during their twenties and randomly allocated into marathon running and control groups. They would then need follow up for 30 years or more during which the marathoners would have to keep up their prescribed amount of exer-

Dr D. R. Hay, medical director of the National Heart Foundation of New Zealand, writes on runners and coronary disorders.

cise. The numbers would need to be sufficiently large to allow for other confounding variables such as personality, varying dietary and smoking habits, etc. At the end of it all one would hope that there had been a sufficient number of deaths or coronary events to answer the original question and ideally all survivors should have an X-ray of their coronary arteries to determine more accurately the amount of coronary disease. It is an impossible study. Exercise and physical fitness does appear to give some protection against coronary disease and it has other worth-while benefits on health. The National Heart Foundation therefore is all for it, but we don’t talk about immunity; and it is misleading to think that there is something specially protective about the marathon. Moreover, exercise can and does kill a few people

— and marathoners are not immune. Despite thorough examination and investigation the occasion- I al runner does come to grief. I should emphasise however, that the vast majority do not, provided that ■ they train gradually and ' sensibly and report any j untoward symptoms such ' as chest pain, faintness or severe breathlessness. Those who have had onary heart attacks can be trained to achieve sur- , prising amounts of exercise including marathon running but this by no means applies to all such ■ patients, and there are many for whom such programmes are totally inappropriate and potential- - ly harmful.