Commentary: Modern stress and coronary heart disease: still problematic

S Leonard Syme

University of California, Berkeley, CA, USA.

It is easy to dismiss this paper.1 Stewart poses an interesting question and then suggests an answer based on clinical speculation, anecdotes, and selective citations from the literature. The paper was published in 1950 and while it is true that there was not a lot of good data available at that time, there was some, and it was not used. Why, then, pay attention to this paper now?

The problem Stewart deals with is the observation of a major increase in coronary heart disease (CHD) during the first half of the 20th century among middle-aged men living in ‘civilized’ countries. He points out, however, that this explosion of CHD is unknown in members of ‘primitive races’. Importantly, he notes that this immunity in primitive peoples disappears when they become exposed to ‘civilized life’. What is it, he asks, about civilized life that could account for this amazing phenomenon?

One would think, even in 1950, that the obvious first-choice candidates to explain this ‘vast’ increase would be such things as changes in diet, blood pressure, obesity, cigarette smoking, or physical activity. These are hardly mentioned in the paper. Instead, Stewart focuses his explanation on emotional stress, ‘modern stress’. The evidence he develops in support of his view is not at all convincing but, in developing his thesis, he makes five important points that are of interest today:

  1. Stewart began with a population fact: the increase of disease in certain population groups. He then sought an explanation for this finding at the population level. He noted that the increase in CHD was primarily evident in professional workers and especially in physicians and surgeons. Those in the lower occupational grades had much lower rates. Explanations of this type of population difference in disease usually are reductionistic: they attempt to explain group data by referring to data on individuals. Stewart more appropriately explores for explanation such ecologic phenomena as changes in the work force, in educational policies, in ‘modern life’. This is an important and innovative departure from the usual practice.
  2. Stewart reviews the evidence for a genetic explanation but concludes that genetic factors are most often predispositions that become important when environmental forces impinge upon them. This was a useful way of thinking about this issue in 1950 and, in this time of the genome, it still needs to be emphasized today. His suggestion for studying the environment is to consider the role of ‘education, occupation, and class’. We are only now beginning to appreciate the importance of these factors.
  3. Stewart considers the role of personality in the aetiology of disease. He notes that investigation of this issue ‘proves a considerable task, since personality not only creates its own endogenous stresses but also determines such factors as occupation, which further introduce the influences of environment’. These comments reflect a thoughtful insight into the role of the unmeasured confounder. Today, we still struggle to understand the role of occupational status in the aetiology of disease; it is useful to remember that people do not sort themselves into occupational categories at random. The role of a variety of unmeasured variables (including psychological factors) in influencing choice of occupation and choice of remaining in or leaving a job is still not well understood, and it needs to be.
  4. This paper is about stress. I had always thought of John Cassel’s 1976 paper on host susceptibility to have been the first careful analysis of the misuse and overuse of this concept. In that paper, Cassel noted ‘the simple-minded invocation of the word stress ... has done as much to retard research in this area as did the concepts of the miasmas at the time of the discovery of microorganisms’.2 I had forgotten that Stewart made essentially the same point 26 years earlier. He said ‘Nowadays it is scarcely possible to open a newspaper without seeing a reference to the "stress" of modern existence. It seems to be held almost universally today that things are pretty tough—bad enough, in fact, to account for almost nothing.’ Stewart then describes a very particular and specific type of stress (competition to succeed) as being of aetiological significance. Whether or not one agrees with his formulation, it is of importance that he attempted the development of this more focussed hypothesis.
  5. There are in this paper many concepts that seem antiquated and hurtful, even considering that the paper was written over 50 years ago. Mention has already been made to the description of people living in England as being civilized, compared to members of the ‘primitive races’. With regard to manual workers, he notes that ‘whatever the size of his pay-packet, he makes a point of spending all that he earns ... scorning to limit his consumption of beer and tobacco ... and investing what little he has on horses, dogs, and football pools. He is content with his lot’. But Stewart also introduces some concepts that are of great significance today. For example, he describes the circumstances of people confronted with disasters such as ‘flood and famine, war and pestilence’. He suggests that these terrible events do not have the same impact on health as other modern problems because they are outside the control of the individual. They are accepted because there is no alternative. People do what they can but they cannot blame themselves for their difficulties. Stewart contrasts this situation to the situation often faced today: a situation where there are many life options and substantial competition and where failure can directly be traced back to one’s self. The consequence of this is to feel a lack of control in shaping one’s destiny and, over time, to lose hope. These failings, he suggests, may have serious implications for health.

While it is easy to find fault with this paper, it is important that we remain humble. Stewart tries to explain the massive increase in CHD in the first half of the 20th century and does not do a very good job. On the other hand, there has been in Britain a massive reversal in the relationship between CHD and socioeconomic status in the second half of the 20th century3 and no one, to my knowledge, has been able to satisfactorily explain that. Nor was anyone able to predict the decline of CHD in the last 50 years of the century. Some argue that these shifts are the result of changes in values, perceptions, behaviour, and stress levels of individuals; others think they are a consequence of shifts in social structures and the environment. Both groups make interesting and important points but we are far from understanding these issues. It is good to re-read Stewart’s paper if only to stimulate us to try to do better.

References

1 Stewart IMcDG. Coronary disease and modern stress. Lancet 1950;867–70.

2 Cassel J. The contribution of the social environment to host resistance. Am J Epidemiol 1976;104:107–23.[ISI][Medline]

3 Logan WPD. Mortality from coronary and myocardial disease in different social classes. Lancet 1952;262:758–59.[ISI]





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