"Tell me, doctor, is epidemiology dangerous!" Michel C. Thuriaux
I
confess that I was disconcerted by this question. In trying to reply I had first of all to think about what epidemiology is, how it is used and why. In one of the oldest texts on epidemiology, Hippocrates of Cos stresses the importance in order to fight the diseases which attack communities - of studying the place (where?), the time (when?) and the characteristics of those communities (who? how?). The epidemiology of the environment and of lifestyles were thus already subjects of concern about 25 centuries ago. Even older texts found in the Indus Valley discussed similar preoccupations as regards water supplies and improvements in sanitation. The development of health statistics in the 17th century made it possible to give better and more systematic answers to the question: how many? which had been more or less evaded until then. Various other factors have since contributed to the development of epidemiology over the last 200 years. The evolution of medicine and public health in the course of the last century led to a better knowledge of infectious diseases and ways of fighting them. (The application of this knowledge is always topical, and resulted in the eradication of smallpox ten years ago, while these methods continue to be applied today, for example, in the fight against AIDS). But even before the existence had been proved, during the second half of the 19th century, of infectious germs and the laws governing their transmission, "the study of water and habits" had already made it possible to take action on the factors that influence health. In 1849 John Snow, after studying the water supply sources in a London district hard hit by cholera, removed the handle of a pump that supplied water which he considered dangerous. Two years earlier, Ignaz Semmelweis caused a sharp drop in the number of women dying in childbirth in Vienna's hospital by calling for midwives and doctors to wash their hands before examining mothers-to-be. 4
Hippocrates said ... "Whoever would study medicine aright ... must consider th e effect of each of the seasons of the year and the differences between them .. . The effect of water on the health must not be forgotten . .. When a physician comes to a district previously unknown to him, he should consider both its situation and its aspect to the winds ... Then. think of the soil. whether it be bare and waterless or thickly covered with soil and we ll watered . . . Lastly consider the life of the inhabitants them selves: are they heavy drinkers and eaters and co nsequentl y unable to stand fatigue . or being fond of work and exercise - eat wisely but drink spa ringly? . . . A physician who understands these subjects we ll . .. would know what epidemics to expect. both in the su mme r and in the winter. and what particular disadvantages threaten ed an individual who changed his mode of life ... He wou ld be very successful in the practice of medicine."
Epidemiology is not limited only to infectious diseases, not by a long way. Our food and the manner in which we eat affect our health. James Lind in the 18th century and Kanehiro Takaki in the 19th showed the role played by food in the fight against scurvy and beri-beri. At the beginning of this century, Joseph Goldberger studied the deficiencies which affected poor people in the United States and which provoked insanity in sufficient numbers to fill the asylums; as a result he developed methods which are still being applied in the epidemiology of disorders related to nutrition. In the same way, our general lifestyles and our working conditions affect health. Last century, in the Mulhouse region of France, LouisRene Villerme had already described the effects of their working conditions on the health of the cotton workers. Closer to our own time, in the 1950s, the epidemiological studies of Richard Doll and Austin Bradford Hill drew attention to the active role of tobacco in lung cancer. These studies provided the basis for the works which have made us better able to identify the risks involved in tobacco and to develop programmes to combat smoking.
WORLD HEALTH ,
June 1989
major health care programmes in the United States. So we can say that epidemiology helps us to identify the factors which Photo T. P. Singh influence our health (by giving answers Facing page: /gnaz Semmelweis (181~ to the questions where, when, who, 1865) and his hygienic basin how much?). The most important encountered the hostility of colleagues question still remains: and then? In who saw no reason for doctors to wash order to reply effectively, it is necessary: their hands before examining women - "Firstly, to know how to draw conin labour. clusions that result from these Photos WHO replies (that is the role of the analyses carried out by epidemiology); Finally, epidemiological methods have been applied to the development - "And secondly, to want to apply those conclusions in support of and use of the health services, whether programmes and policies - or to by comparing methods of intervention develop new ones - that will make (efficacity of the cervical smear in the better health possible (the role of struggle against cancer of the neck of political decision). the uterus) or ways of promoting health, or of establishing what types of It is therefore essential that epidemservice and staff can most efficiently iological knowledge and political will take charge of health care activities. support each other. The member Studies of this type have, for example, countries of WHO recently established made it possible to confirm the precise health goals and drew up effectiveness and usefulness of various categories of personnel in family planning programmes in several counAll photos in th is issue which are not marked tries. One such study provided the WHO or © for copyright are entries in wHo's 40th anniversary International Photo under-pinning for the setting up and Competition. evaluating of nurse practitioners in "Our food and the manner in which we eat affect our health., A meal for poor children in India. WORLD HEALTH ,
policies that would be needed to attain them. They are now striving on a regular basis to collect the vital information which will enable them to measure their progress towards the goals. On the basis of this information, they will then t!y to develop their own new programmes and policies or to improve existing ones. All these will entail considerable changes and readjustments, which are unlikely to be effected without a great deal of heartsearching. Let me come back to the question which began this article. All political action is risky, and no change can come about without risk. In the case of Semmelweis mentioned above, the risk proved to be only too real. Exposed to the hostility of colleagues who could not forgive him for insisting on their washing their hands before examining women in labour, he died insane and in misery in 1865. Without necessarily wishing to go quite so far, it might be useful to recall that, to the degree that it supports health policy or even just politics generally, epidemiology is neither totally harmless, innocent, nor without risk. And perhaps that is not such a bad thing. • 5
June 1989