The angle of vision from a Chair of Social Medicine such as Thomas McKeown occupied with distinction for many years in the University of Birmingham, England, is quite different from that of a physician at the bedside or a surgeon at the operating table. The difference is embodied in the following credo:
I believe that for most diseases, prevention by control of their origins is cheaper, more humane, and more effective than intervention by treatment after they occur.
This belief, McKeown goes on to say, “does not reduce the importance of the pastoral or samaritan role of the doctor. In some ways it increases it.” McKeown firmly repudiates the notion that his message is cognate with that which is embodied in the “Medical Nemesis” by the author referred to in public by the late Professor Henry Miller as “Ivan the Terrible.”
Unfortunately the antithesis between prevention and remedy as McKeown outlines it is very seldom as simple as it might at first sight appear to be as the following examples will show.
We all know very well that the frequency of the congenital affliction known as Down’s Syndrome (formerly “Mongolism” because of Down’s racist propensities) would be greatly reduced if the mean age of motherhood were also to be reduced. But some women want to have—and may for one reason or another only be able to have—a child at the age of thirty or later. Again, the work of Brian MacMahon at the Harvard School of Public Health has shown very clearly that a woman who has had her first child as a teenager stands much less risk of becoming a victim of breast cancer than a woman who has had her first child in her late twenties or a fortiori her thirties. This finding seems to open the door to a number of salutary preventive procedures, but in real life who is going to encourage teenagers—among them one’s own daughters, perhaps—to become pregnant as soon after menarche as possible to give them extra protection in later life against a misfortune that may not befall them anyway? Prophylaxis is not enough: some women will get breast cancer no matter when their children are born, just as some people who don’t smoke will get lung cancer. So no matter how energetic our preventive measures, we must still have the resources of treatment at our command.
In spite of his seniority and distinction McKeown is not above being an enfant terrible. The philosophic doubts which form the subject of this book
…began when I went to a London Hospital as a medical student after several years of graduate research in the Departments of Biochemistry at McGill and Human Anatomy at Oxford. There were two things that struck me, almost at once. One was the absence of any real interest among clinical teachers in the origin of disease, apart from its pathological and clinical manifestations; the other was that whether the prescribed treatment was of any value to the patient was hardly noticed….
Living as I do in a world of medicine and medical research I am happy to be able to affirm that from my own experience what McKeown is saying is absolute bunk.
There is a good deal more in the same vein. He says that
…there seemed to be an inverse relation between the interest of a disease to the doctor and the usefulness of its treatment to the patient.
This was why, so he tells us, “Neurology…attracted some of the best minds”—and that the fascination of multiple sclerosis and amyotrophic lateral sclerosis lay in diagnostic exercises that made little difference to their progress.
Since I know many who are engaged in the treatment of or research into multiple sclerosis, and since I myself do all that is in my power to promote their work, I tentatively put forward an alternate hypothesis: the interest of multiple sclerosis is that it is a terrible disease, cruelly capricious in its incidence. It arouses perhaps more than any other the feelings of compassion that play so large a part in attracting the young into the study of medicine.
It seems to me that McKeown, who temporarily casts himself in the role of St. Peter, weakens his position by resolving to admit dentists into heaven. Not one of us will deny that oral hygiene and the judicious use of fluoride are much preferable to remedial dentistry. But alas, teeth decay in spite of our best endeavors, so we still need dentists—and thank God we have them.
McKeown began to think more deeply about the problems he had just become aware of when he was appointed to a Chair of Social Medicine in the University of Birmingham, his predecessor having been G.A. Auden, father of the poet. In his Chair McKeown came to see himself “as an academic Billy Graham who bears the glad tidings of health for the taking to a grateful people.” He formed the opinion moreover that
medical science and services are misdirected, and society’s investment in health is not well used, because they rest on an erroneous assumption about the basis of human health. It is assumed that the body can be regarded as a machine whose protection from disease and its effects depends primarily on internal intervention.
When McKeown finally gets down to business after an unnecessarily discursive prolegomenon he declares it as his intention to examine “the validity of a concept…on which medical activities largely rest”—the concept that the maintenance of health depends upon the understanding of the structure and function of the body and the disease processes that affect it—an approach which he regards as “mechanistic,” a word which he interprets in the sense of “machine-like” though for many years biologists have taken it to signify “physically determinate.” There follows some uneasy discussion of the mind/ body relationship during the course of which McKeown mentions G.A. Ryle and the notion of “Category-mistakes” without giving me the impression that he altogether understands what he is talking about.
McKeown concedes that the slow “secular” (or long-term) improvement of human health during the nineteenth century occurred pari passu with the growth of our knowledge about the structure and workings of the human body. But he seems impatient with the idea that the former is a consequence of the latter, for he advocates a different view: the reduction of mortality and an improvement of health in human and animal populations are due to the greater abundance and better distribution of nutriment. This transformation annulled a principal constraint upon the growth of human and other populations, a constraint dependent on population density, namely shortage of food. Serious questions can be raised about this view as we shall see.
McKeown’s chapter on “Inheritance, Environment and Disease” has a querulous and dissatisfied air throughout: teachers before the war had urged doctors to become more keenly aware than they had been until then of the gravity and prevalence of cancer of the lung, but he chides them for having paid so little attention to etiology and to discussing the possibility “that the disease might be due to influences which could be modified or removed.” Things are a bit better now, though, McKeown concedes: due attention is given to the importance of smoking, exercise, and diet; moreover, conscientious clinicians, by teaching and example, try to modify the practice of their students and the behavior of their patients. “Nevertheless in medicine as a whole the traditional mechanistic approach remains essentially unchanged; and it will remain unchanged so long as the concept of disease is based on a physico-chemical model.”
I must say I am not clear what McKeown is complaining about. If, as is possible, cancer originates as a somatic genetic accident, this is a physical event which—if it is to be understood—must be understood in physico-chemical terms. The endeavor to understand such a phenomenon is surely not incompatible with an epidemiological analysis that might help to explain its frequency. Most sensible physicians take the view that both approaches are necessary though neither is singly sufficient.
McKeown devotes a considerable number of pages to the subject of “Inheritance, Environment and Disease.” That genetic factors control differences of susceptibility to disease is known to be true of some diseases and not known to be false of any; I look in vain through McKeown’s pages to find a statement of equal clarity and there are other ways in which this chapter disappoints. It can be inferred from McKeown’s discussion on the relative influences of heredity and environment that it is not in general possible to attach any one figure to the proportional contributions of the two to differences in our character makeup (e.g., in respect of IQ scores), but although McKeown allows us to draw this inference it would surely have been better if he had explained why any such exercise is impossible. It is because the contribution made by nature to a character difference is a function of nurture (and that of nurture is a function of nature).
Further, in view of McKeown’s preoccupation with preventive medicine, I had reasonably hoped for some discussion of the merits and shortcomings of the program of J.B.S. Haldane for diminishing the frequency of “recessive” diseases such as phenylketonuria (recessive diseases are those in which the offending gene must be inherited from both parents instead of—as in so-called “dominant” diseases—from only one). The essence of the Haldane solution is the discouragement of marriage, or at all events of childbearing, by possessors of the same damaging recessive gene, a preventive measure which turns upon the fact that most victims of phenylketonuria are the offspring of a marriage between carriers of the offending gene. The shortcomings of this in many ways admirable proposal are first that carriers of recessive genes are not always identifiable and secondly that such a procedure as Haldane recommends would suspend the action of natural selection altogether and pile up still greater difficulties for future generations. Another difficulty is that putting the Haldane scheme into effect would cause a tremendous outcry from all intent upon defending the right—nay, privilege—of parents to bring into the world biochemically crippled or otherwise disadvantaged children.
The second part of McKeown’s book is called “Determinants of Health”; my spirits at once rose because McKeown is admirably well qualified to write authoritatively on the causes of the vast secular improvement in human health that has taken place over the last few centuries.
During most of man’s existence it is probable that a considerable proportion of all children died or were killed within a few years of birth …out of ten newborn children, on average, two to three died before the first birthday, five to six by age six and about seven before maturity. In technologically advanced countries today, more than 95 percent survive to adult life.
The statistical characteristic most dramatically affected by a reduction infantile mortality is of course the mean expectation of life at birth. McKeown does well to point out how enormously it has increased over the period during which reliable records of mortality have been kept; in Sweden it rose from between thirty and forty years in 1700 to seventy-two years for males and seventy-seven for females in 1970. Although the available records “leave no doubt that death rates were falling from the beginning of the nineteenth century…there is impressive indirect evidence that the decline began somewhat earlier, probably in the first half of the eighteenth century.”
To interpret these figures McKeown says we must turn to national records of the causes of mortality which are available for England and Wales since 1838. Insofar as it is possible to interpret the bills of mortality it seems that nearly 90 percent of the total reduction of the death-rate from the beginning of the eighteenth century until today can be credited to the decline of infectious disease. The different infectious diseases contributed unequally to this decline, respiratory tuberculosis contributing most and infections of ear, pharynx, and larynx least. The standardized death-rate from smallpox in England and Wales fell from seventy-five per million in 1848-1854 to two per million in 1971. The corresponding figures for scarlet fever and diphtheria were 1,016 and zero. Needless to say mortality statistics do not assess the gravity and social or personal burden of a disease; although mortality from measles is way down, it was at one time feared—for reasons subsequent research has not upheld—that multiple sclerosis, surely one of the worst of all diseases, was a late complication of measles.
The information that McKeown collates in these pages is interesting not only for those with a taste for statistical figures but also for anyone drawn to social history. Thus it is especially interesting and rather shocking to learn how great a contribution infanticide has made to infant mortality; Disraeli, McKeown tells us, “believed that infanticide ‘was hardly less prevalent in England than on the banks of the Ganges.’ ” McKeown reminds us, too, that both criminal and legal abortion are widespread and on the increase.
I agree with McKeown’s assessment of the importance of infectious diseases in human mortality. I agree also with Haldane (whose name I do not see referred to in McKeown’s book) that death from infectious disease is the most important selective force that has acted upon mankind and that it has left a very nearly indelible stamp on the human genetic constitution. To give one example only: the prevalence in West Africa of the gene which converts hemoglobin A into hemoglobin S seems to be owing to the fact that those who inherit this gene from one parent only enjoy a significant degree of protection against subtertian malaria. The gene does not cause major disability except when it is inherited from both parents, when it gives rise to the grave and usually fatal blood disease known as sickle cell anemia, causing a loss of life statistically outweighed by the gain in protection from malaria. This is an instructive example because it is important evidence for the contention that improvement of the environment—the practice of “euphenics” as President Joshua Lederberg of Rockefeller University calls it—can lead to genetic improvement (in this case the disappearance of gene S) rather than to genetic deterioration.
The causes of the great secular decline in mortality to which I have referred is one of the great problems of social medicine. In view of the nature of his thesis, it is not surprising that McKeown should quote with approval a passage from a presidential address to the American Association of Immunologists that attributes the secular improvement in health to the establishment of a new equilibrium between infectious organisms and their victims, “quite regardless of our therapeutic efforts. According to this interpretation,” McKeown comments, “the trend of mortality from infectious diseases was essentially independent of both medical intervention and the vast economic and social developments of the past three centuries.”
Professors of social medicine usually hold sewers in high esteem so it strikes me as surprising that McKeown evidently does not regard the institution of main sewage disposal systems as one of the “social developments” to which he refers in the passage quoted just above. McKeown doesn’t think much of anti-toxins; nor, I must say, do I. I have however very little doubt of the efficacy of active immunization by toxoid substances, the evaluation of which is going to be complicated by the fact that today, persons specially at risk of contracting, say, tetanus are singled out for protective immunization and generally receive it if they have sensible and responsible physicians and employers. It is true, though, that cholera vaccine has not been proved to be efficacious. Polio vaccine, however, has been. As a medical scientist my own inclination is to give more weight to the success of the latter than the failure of the former but McKeown is determined to give the lion’s share of the credit to the operation of natural selection: “The immunological constitution of a generation is influenced largely by the mortality experience of those which precede it.”
I should be the last to depreciate the importance of natural selection and of evolutionary changes generally, but if they were a fully adequate safeguard against disease we should not get half the diseases we do. Dr. David Pyke has shown, for example, that there is a clear-cut genetic element in susceptibility to the form of diabetes that presents itself in middle age or in older people. There is also a genetic element, though of a different kind, in differences of susceptibility to insulin-dependent diabetes of juvenile onset. The forces of natural selection working upon what was at one time a mortal complaint of early onset are immensely strong; but they have not been strong enough to eliminate the genetic constitution associated with a specially high susceptibility to insulin-dependent diabetes.
McKeown’s views on the importance of nutrition in resistance to infectious disease are succinctly summarized as follows:
If the decline of mortality from infectious diseases was not due to a change in their character, and owed little to reduced exposure to micro-organisms before the second half of the nineteenth century or to immunization and therapy before the twentieth, the possibility that remains is that the response to infections was modified by an advance in man’s health brought about by improved nutrition.
McKeown’s case is founded upon the undoubted correlation between nutritional standing and susceptibility to infection, but since “there is no direct evidence that nutrition improved in the eighteenth and early nineteenth centuries,” we feel let down.
I shall use McKeown’s own words to describe what he regards as evidence of improvement of food supply—his own words, lest in paraphrasing what he says I should be thought guilty of presenting an argument in such a way as to discredit him:
The most impressive evidence of the improvement in food supplies is…the fact that the expanded populations were fed essentially on home-grown food. The population of England and Wales increased from 5.5 million in 1702 to 8.9 in 1801 and 17.9 in 1851. Since exports and imports of food during this period were relatively small, it is clear that food production at least trebled to sustain an increase of 12.4 million in a century and a half.
The decline of mortality that occurred during the eighteenth and nineteenth centuries continued into the twentieth, but with the difference that in the twentieth century the reduction in mortality from noninfectious causes began to make an important contribution to the decline, particularly in respect of prematurity and diseases of early infancy. Deaths attributed to “old age” diminished also, probably because improvements in diagnosis caused them now to be attributed to specific causes.
Infanticide, an important cause of death until at least the latter half of the nineteenth century, diminished during the twentieth, partly because the institution of foundling hospitals made it possible to dispose of children without killing them and partly because of the growth of contraceptive practices. The foundling hospital in St. Petersburg, McKeown reports, had 25,000 children in the mid 1830s on its rolls and admitted 5,000 annually; 30-40 percent of the children died during the first six weeks and hardly a third reached the age of six. Those who denounce birth control procedures as morally the equivalent of murder might now pause to reflect that the reduction in the number of unwanted births has reduced the frequency of child murder—in a real, not figurative, sense.
McKeown summarizes the argument of the first and larger half of his book in terms which escape tautology only by a hair’s breadth. The improvement of health that has taken place during the past three centuries was due
…not to what happens when we are ill, but to the fact that we do not so often become ill; and we remain well, not because of specific measures such as vaccination and immunization, but because we enjoy a higher standard of nutrition and live in a healthier environment. In at least one important respect, reproduction, we also behave more responsibly.
Turning now to the future McKeown is simplistic to a degree that takes my breath away: “there are only two ways in which disease occurs. It results either from errors in genetic programming at fertilization, or from…an environment for which the genes are not adapted.” To me, a biologist, this remark is about as illuminating as to be informed that disease is caused by a departure from a state of health.
These profundities usher in passages which Jean-Jacques Rousseau would surely have applauded—passages in which McKeown says that whereas genetic adaptations in response to the impact of infectious diseases may occur “within a few generations,” the requirements for health of the digestive, cardiovascular, and reproductive systems do not differ greatly from those which prevailed during man’s evolution—during which we were all nomadic and had practices in respect of diet and the expenditure of energy that were profoundly changed by the agricultural revolution and the accompanying domestication of man, and were of course still more greatly changed by the coming of industry. These passages pleased me because they are evidence that even an expert on social medicine still essentially falls in with the theory of illness that prevails throughout most of the Western world; I mean the “punishment” theory of illness, according to which illness is a judgment upon us for indolence, sloth, gluttony, or other forms of carnal self-indulgence. These are salutary reflections that reaffirm the importance of the regulation of personal conduct. A new theory of illness is now taking shape at a time when the detritus of civilization is accumulating around us: the environment gets blamed for more and more that goes amiss and it is becoming increasingly easy to blame the environment or the iniquities of laissezfaire capitalism rather than, as in the old days, ourselves for our medical misadventures.
When he turns to considering our health in the future McKeown seems to me again to use too broad a brush for what is in any case too large a canvas. “Most types of mental subnormality and of congenital malformations,” he writes, are the consequence of prenatal environmental influences; that, surely, is too sweeping a statement.
We can only agree, though, that diseases of a kind which McKeown attributes to faulty genetic programming are relatively intractable, where diseases associated with affluence are in principle preventable. A miscellaneous group of diseases is classified as potentially preventable: “some acute respiratory infections, such as the common cold, influenza and viral pneumonia as well as gastrointestinal diseases due to viruses. More tentatively, I suggest that many psychiatric conditions are in the same class.”
In a synoptic survey of the achievements of medicine McKeown makes the familiar and important point that the death-rate from tuberculosis underwent a progressive decline that was independent of the introduction of specific remedial measures. On the other hand he is inclined to dismiss as “perverse” Creighton’s view that vaccination played virtually no part in the decline of mortality from smallpox. Since he later expresses doubts on the efficacy of medical research it is heartening to see how clear is the evidence of the beneficial effects of vaccination against poliomyelitis.
It is fully in keeping with the character of McKeown’s book that he doesn’t think very much of medical research and that he should quote with delighted approbation Sir Macfarlane Burnet’s extraordinary lapsus mentis in which he said that the contribution of laboratory science to medicine had come virtually to an end. The reason he took this view, I believe, is that Macfarlane Burnet was formerly, as I was, the head of a large medical research institute devoted to “basic” medical research and that he was as dismayed as I was at the fact that so many members of his staff were more intent upon enlarging their own reputations as “pure scientists” than in engaging directly upon the study of medical problems.
I now think that Burnet was quite wrong and that young scientists intent upon improving natural knowledge, and Lewis Thomas, who champions them, are right. As an antidote to Burnet’s spiritless declaration I roundly declare that within the next ten years remedies will be found for multiple sclerosis, juvenile diabetes, and at least two forms of cancer at present considered somewhat intractable. These remedies, moreover, will come from medical research laboratories, very likely from people ostensibly working on some quite different subject.
It is one of the sadnesses of medical education that in spite of the earnest advocacy of people in the know, ordinary medical students tend to be bored by and are even a little contemptuous of the study of social medicine and public health. In British medical schools public health is traditionally taught alongside forensic medicine, in a course compendiously known to medical students as “rape and drains.” I should now hazard an explanation of why so many medical students depreciate the importance of social medicine because it will help to explain why McKeown’s book is likely to leave so many of its readers with a feeling of uneasy dissatisfaction. Social medicine, as McKeown expounds it in his book, has to do with the illnesses and mortality of whole populations and with how they vary from time to time and from place to place. On the other hand the feelings of compassion that are thought to tempt young students into medicine soon make them realize that it is individual people, not populations, that are ill and in need of treatment. For this reason I think it likely that medical education and medical research will for many years to come remain centered upon personal rather than social medicine.
May 15, 1980