The Burden of Prudence – Industrialisation and Disease

Thomas McKeown

  • Western Diseases: Their Emergence and Prevention edited by H.C. Trowell and D.P. Burkitt
    Arnold, 456 pp, £28.50, March 1981, ISBN 0 7131 4373 8
  • The Diseases of Civilisation by Brain Inglis
    Hodder, 371 pp, £10.95, September 1981, ISBN 0 340 21717 0

Although these books have different titles, their subjects are the same: the diseases which have replaced the infections as the predominant causes of sickness and death in technologically advanced societies. The editors of Western Diseases give two reasons for preferring their title to ‘Diseases of Civilisation’: some of the diseases were present, although uncommon, in the ancient civilisations of Egypt, Greece, Rome and China; and the implication that countries where their incidence is low are uncivilised gives offence in the Third World. Neither title is really satisfactory, however. The term ‘Western’ can be used only metaphorically in relation to developed countries such as Australia, New Zealand and South Africa, and in time will need to be applied widely in Asia, Africa and Latin America as the character of health problems changes with economic development. The objection to attributing the diseases to civilisation is that they have become significant only in the last few centuries, in some cases in the last few decades; the infections were still predominant in Renaissance Italy, Elizabethan England and 17th-century France. The common causes of sickness and death in advanced societies are therefore more accurately regarded as diseases associated with industrialisation.

Although the issues discussed in the two books are often overlaid by financial, political and professional considerations, they are arguably as fundamental as those that arise in the current debate on Darwinism. The basic questions are these: which are the influences that determine man’s health and what steps are needed to preserve it? The answers turn largely on evaluation of two approaches to the management of disease, one through control of disease origins, the other through intervention by treatment in disease mechanisms. The conclusion in both books is that the first approach has much more to offer than the second, but the grounds for this view, and the steps which it is suggested should follow from it, are quite different in the two cases.

Hugh Trowell and Denis Burkitt are a distinguished physician and surgeon who have spent most of their professional lives in Africa; with T.L. Cleave and G.D. Campbell, they have probably contributed more than anyone else to our understanding of the relation between the health problems of developed and developing countries. In Western Diseases they bring together reports by 34 contributors, who describe their experience of changes in the pattern of disease in several countries as Westernisation occurs. There are four main lines of evidence, which the editors admit are not all equally secure. 1. Until recently many of the non-communicable diseases now predominant in the West were uncommon or absent in hunter-gatherers and peasant agriculturists. 2. When these populations change from their traditional ways of life to those of the developed countries, they begin to exhibit the Western pattern of disease. 3. The incidence of some of the diseases has declined in Western populations which have reversed certain features of their lifestyle to bring it closer to that of peasant agriculturists. 4. Of the multiple influences responsible for the Western pattern of disease, dietary changes are probably the most important.

The evidence assembled on the first two points is impressive. Before 1940, in Africans of Kenya and Uganda, blood pressure did not rise with age and essential hypertension was rarely seen: it is now a common disease. Obesity was almost unknown in 1930 when Julian Huxley noted with amazement that ‘almost the only fat woman I saw in Africa’ worked in the Nairobi brewery. Now, however, ‘the towns of East Africa contain many fat upper-class Africans; their leaders seen on television are often grossly obese.’ (Trowell suggests that obesity and the associated diabetes probably emerged as common disorders in the English upper classes in the late 18th century, when sugar was first reported in the urine.) In Kenya in the 1930s, diabetes was rare in Africans but not in Europeans and Indians: today there are large diabetic clinics in all town hospitals. Cerebrovascular disease was the first arterial disease of clinical significance to emerge in Africans: before 1948 a case due to essential hypertension was rarely or never seen; in 1970 it was the commonest cause of death in a large series of neurological patients in a Ugandan hospital. Coronary heart disease is said to be the last major cardiovascular Western disease to appear – the first clinical reports of cases were made quite recently in Uganda (1956) and in Kenya and Tanzania (1968). Michael Gelfand, a very experienced physician, writes that ‘coronary thrombosis has begun, only recently, to emerge in Zimbabwe Africans and angina remains a rare disease.’

On the basis of observations of this kind from many parts of the world, Trowell and Burkitt have prepared a provisional list of Western diseases. In addition to those already mentioned, it includes cholesterol gallstones, varicose veins, constipation, appendicitis, diverticular disease, haemorrhoids, cancers of the bowel, breast and lung and dental caries. It is already a formidable list, and may have to be extended as further evidence becomes available. While there may be differences of opinion about the acceptability of some of these conditions as Western diseases, the general conclusion that many of them are now appearing in developing countries where formerly they were rare is not in doubt.

It is more difficult to ascertain the nature of the influences which have led to the Western pattern of disease, and the extent to which the pattern can be reversed by changes in ways of life. Diets high in carbohydrate and fibre and low in fat are reported to be beneficial in adults with diabetes. Blood-pressure levels fell in hypertensive patients whose intake of salt in the form of sodium chloride was drastically reduced. The addition of wheat bran to make a high fibre diet is effective in the prevention and treatment of constipation, and is said to be of value in treatment of some other conditions such as haemorrhoids and diverticular disease. Far more extensive claims are made for the work of a Longevity Centre in Santa Barbara, where modified diets are used in association with increased exercise and elimination of smoking, alcohol and caffeine. Promising, in some cases dramatic short-term improvements are reported in patients with diabetes, hypertension and some other types of heart disease. In summarising the work relating Western disease to specific influences, the editors conclude that it is only in ischaemic heart disease and some varieties of cancer that exacting scientific requirements have been met. Nevertheless they regard the evidence as highly suggestive in dental caries, obesity and diabetes mellitus and believe that in time several other diseases will be added to the list. And while recognising the role of other influences, they look particularly to dietary measures for effective prevention.

Quite different views are expressed in The Diseases of Civilisation, the latest in the series of books in which Brian Inglis has examined orthodox and unorthodox forms of medicine. His conclusions are based on a careful, if selective examination of the literature on some of the common causes of sickness and death, including heart disease, cancer, mental illness and infectious diseases. He discusses at length subjects which are hardly mentioned in Western Diseases – for example, the ineffectiveness and hazards of conventional medical treatment – but arrives at the same conclusion: that a new approach to disease management is needed. However, diet, which Trowell and Burkitt think is so important, is referred to only incidentally, along with exercise, smoking and the like, as contributory influences in the causation of disease. His main emphasis is on the significance of stress. He quotes extensively the evidence that stress plays an important part in the origin and course of the diseases he examines, including the infections, and concludes that ‘for the immediate future, the most valuable weapon which the public possesses’ is the knowledge ‘that in so far as stress is a cause, precipitant or risk factor in disease, it is not such because of the impact of the stressor, but because of the reaction of the individual to the stressor.’ Inglis suggests that this knowledge can be applied, particularly in the case of those identified as being at risk, by learning how to avoid stress or, better, by learning how to react less violently to stressors. Techniques such as relaxation, meditation and biofeedback are available for this purpose.

One can recognise the enormous importance of stress without accepting the generality of these conclusions. Multiple influences are involved in the causation of the diseases, and their relative importance is not the same in every case. For example, the rapid decline of tuberculosis during the period of industrialisation is more credibly explained by improvements in nutrition than by reductions in stress. In the Third World today, the provision of sufficient food and clean water would contribute far more than other measures to the control of infectious diseases. The dietary changes recommended by Trowell and Burkitt offer the most promising approach to some of the intestinal diseases and possibly to the control of hypertension. The observation of a relationship between personality and proneness to lung cancer would not change the conclusion that elimination of smoking is the most effective means of preventing the disease. Indeed, in the light of experience of screening policies, I am doubtful whether the division of a population into groups with greater or lesser risk of disease is very useful, except in the case of occupational and similar hazards. Selye, the pioneer of work on stress, clearly recognised the importance of controlling the origin of diseases as well as the response when he wrote: ‘No disease is purely a disease of adaptation, any more than a disease of the heart or an infectious disease is a “pure disease” in which adaptive phenomena play no part. The term “diseases of adaptation” should be used only when the maladaptation factor appears to be more important than any existing pathogen itself.’ This criterion is not met in lung cancer, constipation, obesity, tuberculosis and food poisoning, to give only a few examples.

The objection that will be raised to the conclusions in Western Diseases is that the evidence is very incomplete, particularly on the nature of the influences responsible for the changing disease pattern. Some medical scientists are particularly uncomfortable with the reliance on anecdotal evidence and clinical impressions. (The editors remind them that these were the bases of their own highly regarded work on kwashiokor and Burkitt’s lymphoma.) The history of medicine is littered with accounts of ineffective and dangerous remedies which were applied without adequate scientific appraisal. The critics find it paradoxical that at a time when epidemiologists are insisting on randomised control trials before new methods of investigation and treatment are introduced, they themselves are advocating major modifications of public policy which have insufficient justification. If resources are wasted by the widespread use of an ineffective clinical procedure, the financial and other consequences of an ill-founded change from butter to margarine or from refined flour to wholemeal would be equally serious. It is therefore said to be unacceptable to change national food policies, to prohibit certain kinds of advertising, to control suspected hazards in industry or to attempt to modify behaviour, except in cases such as cigarette smoking where the evidence is thought to be convincing.

It is fortunate that these requirements were not imposed in the past. When the population of London was protected from cholera in the 19th century by removal of the handle of a water pump, neither micro-organisms nor tests of significance had been discovered. If thalidomide had not been withdrawn when knowledge of teratogenesis was very incomplete – as it still is – thousands of children would have been born with limb deformities. If the argument that an association does not prove causation and that only experimental evidence is convincing had been accepted, many people who found the relation between smoking and lung cancer sufficiently impressive to give up cigarettes would have died from the disease before beagles and hamsters had been taught to smoke. And if the limited foods available during the last war had not been distributed judiciously by rationing, subsidies and supplements, the health of the population would have been much less satisfactory than in fact it was. Yet it was not then, nor is it now, possible to specify with any precision the mode of operation of the nutritional influences that were effective.

There is little doubt that Trowell and Burkitt are correct in believing that it is possible to outline ways of living which improve the prospects for a long and healthy life. Shaw said one should take care to get born well: a perceptive foetus would be well-advised to consult standardised mortality ratios, statistics which express the relative risk of death according to age, sex, occupation, place of residence and so on. It would give itself excellent prospects for health by electing to become the wife of a rural clergyman; well-to-do but living frugally; fertile but with few children; physically active but avoiding field sports, especially hunting; taking no drugs, alcohol or tobacco; and keeping to a diet low in salt, fat, sugar and meat, and so rich in fruit, vegetables and grains that the addition of bran would be an indulgence. Of course we cannot all be wives of rural clergymen: nevertheless it is possible to progress towards ways of life which retain the advances on which our present health largely depends, but remove some of the environmental and behavioural hazards which threaten health because they depart radically from the conditions under which our ancestors evolved. It should be admitted frankly that in the foreseeable future the evidence for some of the changes will be incomplete. To assess precisely the respective roles of diet, exercise and smoking in the causation of coronary heart disease, a massive human experiment would be needed; it is complicated by the fact that the relative importance of these influences probably differs in different environments (in the same way that the contributions of inheritance and environment to IQ also vary according to the environment). It will therefore be necessary sometimes to act on high, or even moderate, probabilities, on what has been called a ‘burden of prudence’ rather than a ‘burden of proof’. In this approach, if there are substantial experimental, clinical or epidemiological reasons for thinking an influence is harmful, it should so far as possible be removed until it has been shown that the fears are groundless.

In discussions of the changing pattern of disease it is generally assumed that the infections were the diseases of the past and that the non-communicable diseases which have partially replaced them are the problems of the indefinite future. It is possible that in time the roles may again be reversed. If we are correct in thinking that the new pattern is largely the result of environmental and behavioural changes associated with industrialisation, many of the influences could be removed without prejudice, and in some cases with benefit, to the quality as well as to the duration of life. To assume that behaviour will not be modified for health purposes is not only to take a gloomy view of man’s educability: it is also to overlook the enormous changes which have occurred during the last few centuries. After all, it is not long since our ancestors were practising infanticide, spitting on floors, tipping chamber-pots into the street and producing large numbers of children without regard for the consequences.

Man’s long-term relation to his parasites is a far more open question. Where it is possible to prevent contact with them, as in the case of organisms spread by water and food, there is no reason to doubt that control will continue to be effective. We cannot have the same confidence about disease caused by micro-organisms normally found in the body, or conveyed by vectors such as the mosquito, tick or snail. J.B.S. Haldane suggested that the Almighty must have been inordinately fond of beetles. On the evidence of the ability of some of the common disease vectors to resist the measures directed against them, he must have had a strong attachment to the arthropods in general. Moreover, the disappearance of an infectious disease provides no certainty that it has gone for ever. Smallpox, for example, is said to have been eradicated, but we can hardly believe that the virus, or others capable of evolving into it, has disappeared for ever from the animal reservoirs from which, presumably, it originally emerged. Predictions about future health trends are notoriously hazardous, but my own guess is that a hundred years from now it is more likely that wholemeal will have replaced refined flour, that fat, salt and sugar consumption will be low, and that smoking will be assigned a place somewhere between spitting and the taking of hard drugs – about as unpleasant as the one if not quite so lethal as the other – than that diseases such as influenza, malaria and the common cold will have been eradicated.