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Clinical epidemiology and the use of words
Letters to the Editors
962
CLINICAL
EPIDEMIOLOGY
A recent article by Naylor et al. [l] discussed the problem of the terms “clinical” and “population” epidemiology and reviewed the argument about these terms that has been going on for the past few years. As Naylor and his colleagues point out, part of the problem arises through Sackett and colleagues’ book Clinical Epidemiology-a Basic Science for Clinical Medicine [2]. This is an excellent textbook for medical students, but it seems to suggest that epidemiology is a basic science exclusively for clinical medicine. The difficulty with these terms is that they conjure up labels, divide people, classify subjects and in the end obscure the function of the epidemiologist. If epidemiology is defined as the subject as taught in universities and medical schools a clear purpose to the subject is seen. The epidemiologist is one who develops a methodology for, undertakes research in and teaches the subject. Epidemiology, as defined by Last, is “the study of the distribution and determinants of healthrelated states or events in specified populations, and the application of this study to control of health problems” [3]. However, in the practical world in service situations, what do epidemiologists actually do? If they are concerned with infectious disease then they can study the occurrence of cases, set up surveillance systems and provide advice on and investigation into prevention and control of epidemics. If they are concerned with chronic disease they have a more difficult task since no clear single solution is usually available for the most common conditions. Epidemiologists really face a problem defining their role as the terms “clinical” and “population” epidemiology have evolved. Clinicians have a very clear role to play in the diagnosis, treatment and management of individual patients. They may apply epidemiology to improve methods of diagnosis, management and care. If they are in public health, responsible for the health of defined communities they will be dependent on epidemiology to provide them with the necessary knowledge on the distribution of disease and of factors in the environment which may predispose towards the development of disease and this knowledge may help in preventing the spread of disease. Thus we have two protagonists: one a clinician calling himself a clinical epidemiologist
AND THE USE OF WORDS and the other a public health physician calling himself a population epidemiologist. Neither of these individuals is trying to harm the other. Both are, however, trying to develop a discrete identity. As an epidemiologist, I am involved in the development of methods for the study of healthrelated events and with the investigation of optimal provision of health and other services to cure, care for and prevent disease in a population made up of individuals. As clinicians, Sackett and his colleagues are concerned with the provision of the best and most costeffective methods of diagnosing and treating individuals. The two approaches are obviously complementary. The basic principles of epidemiology are applicable to both clinical practice and public health practice and no argument exists on this. There is, however, a vital need to develop a proper rationale for the role of the epidemiologist in the service setting rather than the academic setting which is already more strictly defined. Those involved in public health practice have a clear mandate. They use epidemiology as the basic science in addition to other basic and social sciences. Clinicians, similarly, use epidemiology as one of the methods that they apply in their armamentarium for decision-making on the treatment of disease. The real problem that we, as epidemiologists, face now is not “Should we label ourselves one type of epidemiologist or another?’ It is “How can we help to make more effective use of the limited resources that are available for both the prevention, care and treatment of disease?” The major problems for epidemiologists concern the determination of priorities. Who should be treated and how? What is the approximate mix of services? How can we best prevent people getting disease? In countries where more profligate use is made of health resources, perhaps the major concern is the treatment of individuals rather than the treatment of population groups, even though significant groups may receive inadequate treatment. In most of the world, however, the real difficulty is how do we prevent diseases that can be prevented; how can we minimize the burden of disease?
Letters to the Editors
One failing that epidemiologists have is excessive concentration on refinements of methodology without concern for those conditions in which major advances need to be made. This is as true in the developed as in the developing world. The majority of epidemiologists are concentrated in working on a few conditions which may cause many deaths. If we review the contributions made in the past 20 years to our knowledge on the prevention and treatment of the major burdens on health, viz. cancer, cardiovascular disease, respiratory disease and infectious disease, most of the effective known methods and factors were already described 20 or more years ago. In spite of this the amount of person-hours devoted to their study has increased over this time. Diseases such as arthritis, mental illness, neurological illness, which also place a heavy burden on sufferers and their families, both in the western world and now in the developing countries, have not attracted our discipline to the same extent, only partly due to inadequate resources. Only in AIDS has there been a greater expansion and attraction of new work and new epidemiologists. In the developing world there are innumerable conditions amenable to prevention and yet we have done little to support such efforts. Only in a few conditions such as smallpox has there been any success. Silman and Allwright [4] have recently summarized efforts to eradicate or eliminate a number of conditions from Europe. It is of concern that we spend our time arguing about the proper or improper use of descriptive adjectives when in fact our profession is neglecting important problems that require to be tackled.
963
Epidemiology needs to be used under a wide variety of conditions, under different circumstances, both in service as well as in the universities. I would hope that we would continue to call ourselves epidemiologists without any labelling adjectives-thus restoring the prime purpose of our subject and not attempting to delineate particular sub-groups and their interests. The clinician may use epidemiology. The public health practitioner, however must use epidemiology in his work. However, to be successful he has to be more than an epidemiologist. He must be concerned with the use of his subject and its applications to public health. The clinician uses epidemiology in the management of the individual and sees the results. The public health practitioner does the same on a population-wide basis. The differentiation of epidemiology into “clinical” and “population” epidemiology distracts from the major task which is the application of epidemiological findings to improve health. W. W. HOLLAND Department of Public Health Medicine United Medical and Dental Schools St Thomas’ Campus London SE1 7EH U.K.
REFERENCES Naylor CD, Basinski A, Abrams HB, Detsky AS. Clinical and population epidemiology: beyond sibling rivalry? J Clin Epidemiol 1990; 43: 607411. Sackett D, Haynes RB, Tugwell P. Clinical Epidemiology-a Basic Science for Clinical Medicine. Boston: Little Brown; 1985. Last JM (Ed). A Dictionary of Epidemiology. New York: Oxford University Press; 1988. Silman AJ, Allwright SPA. Elimination or Reduction of Diseases? Oxford: Oxford University Press; 1988.
Response
Dr Holland’s letter reminds us that the commonality between clinical and population epidemiology extends beyond the realm of tools used for research, and into the service roles of clinicians and public health practitioners. I am grateful for his comments and agree with almost all the points made, but a few clarifications are in order.
We did not actually argue that Drs Sackett, Tugwell and Haynes had contributed to the problem of “sibling rivalry” [l] by subtitling their textbook A Basic Science for Clinical Medicine [2]. Although the McMaster primer is oriented primarily to medical students and residents, this may reflect the authors’ priorities in pedagogy, or their view of clinical epidemiology,
962
CLINICAL
EPIDEMIOLOGY
A recent article by Naylor et al. [l] discussed the problem of the terms “clinical” and “population” epidemiology and reviewed the argument about these terms that has been going on for the past few years. As Naylor and his colleagues point out, part of the problem arises through Sackett and colleagues’ book Clinical Epidemiology-a Basic Science for Clinical Medicine [2]. This is an excellent textbook for medical students, but it seems to suggest that epidemiology is a basic science exclusively for clinical medicine. The difficulty with these terms is that they conjure up labels, divide people, classify subjects and in the end obscure the function of the epidemiologist. If epidemiology is defined as the subject as taught in universities and medical schools a clear purpose to the subject is seen. The epidemiologist is one who develops a methodology for, undertakes research in and teaches the subject. Epidemiology, as defined by Last, is “the study of the distribution and determinants of healthrelated states or events in specified populations, and the application of this study to control of health problems” [3]. However, in the practical world in service situations, what do epidemiologists actually do? If they are concerned with infectious disease then they can study the occurrence of cases, set up surveillance systems and provide advice on and investigation into prevention and control of epidemics. If they are concerned with chronic disease they have a more difficult task since no clear single solution is usually available for the most common conditions. Epidemiologists really face a problem defining their role as the terms “clinical” and “population” epidemiology have evolved. Clinicians have a very clear role to play in the diagnosis, treatment and management of individual patients. They may apply epidemiology to improve methods of diagnosis, management and care. If they are in public health, responsible for the health of defined communities they will be dependent on epidemiology to provide them with the necessary knowledge on the distribution of disease and of factors in the environment which may predispose towards the development of disease and this knowledge may help in preventing the spread of disease. Thus we have two protagonists: one a clinician calling himself a clinical epidemiologist
AND THE USE OF WORDS and the other a public health physician calling himself a population epidemiologist. Neither of these individuals is trying to harm the other. Both are, however, trying to develop a discrete identity. As an epidemiologist, I am involved in the development of methods for the study of healthrelated events and with the investigation of optimal provision of health and other services to cure, care for and prevent disease in a population made up of individuals. As clinicians, Sackett and his colleagues are concerned with the provision of the best and most costeffective methods of diagnosing and treating individuals. The two approaches are obviously complementary. The basic principles of epidemiology are applicable to both clinical practice and public health practice and no argument exists on this. There is, however, a vital need to develop a proper rationale for the role of the epidemiologist in the service setting rather than the academic setting which is already more strictly defined. Those involved in public health practice have a clear mandate. They use epidemiology as the basic science in addition to other basic and social sciences. Clinicians, similarly, use epidemiology as one of the methods that they apply in their armamentarium for decision-making on the treatment of disease. The real problem that we, as epidemiologists, face now is not “Should we label ourselves one type of epidemiologist or another?’ It is “How can we help to make more effective use of the limited resources that are available for both the prevention, care and treatment of disease?” The major problems for epidemiologists concern the determination of priorities. Who should be treated and how? What is the approximate mix of services? How can we best prevent people getting disease? In countries where more profligate use is made of health resources, perhaps the major concern is the treatment of individuals rather than the treatment of population groups, even though significant groups may receive inadequate treatment. In most of the world, however, the real difficulty is how do we prevent diseases that can be prevented; how can we minimize the burden of disease?
Letters to the Editors
One failing that epidemiologists have is excessive concentration on refinements of methodology without concern for those conditions in which major advances need to be made. This is as true in the developed as in the developing world. The majority of epidemiologists are concentrated in working on a few conditions which may cause many deaths. If we review the contributions made in the past 20 years to our knowledge on the prevention and treatment of the major burdens on health, viz. cancer, cardiovascular disease, respiratory disease and infectious disease, most of the effective known methods and factors were already described 20 or more years ago. In spite of this the amount of person-hours devoted to their study has increased over this time. Diseases such as arthritis, mental illness, neurological illness, which also place a heavy burden on sufferers and their families, both in the western world and now in the developing countries, have not attracted our discipline to the same extent, only partly due to inadequate resources. Only in AIDS has there been a greater expansion and attraction of new work and new epidemiologists. In the developing world there are innumerable conditions amenable to prevention and yet we have done little to support such efforts. Only in a few conditions such as smallpox has there been any success. Silman and Allwright [4] have recently summarized efforts to eradicate or eliminate a number of conditions from Europe. It is of concern that we spend our time arguing about the proper or improper use of descriptive adjectives when in fact our profession is neglecting important problems that require to be tackled.
963
Epidemiology needs to be used under a wide variety of conditions, under different circumstances, both in service as well as in the universities. I would hope that we would continue to call ourselves epidemiologists without any labelling adjectives-thus restoring the prime purpose of our subject and not attempting to delineate particular sub-groups and their interests. The clinician may use epidemiology. The public health practitioner, however must use epidemiology in his work. However, to be successful he has to be more than an epidemiologist. He must be concerned with the use of his subject and its applications to public health. The clinician uses epidemiology in the management of the individual and sees the results. The public health practitioner does the same on a population-wide basis. The differentiation of epidemiology into “clinical” and “population” epidemiology distracts from the major task which is the application of epidemiological findings to improve health. W. W. HOLLAND Department of Public Health Medicine United Medical and Dental Schools St Thomas’ Campus London SE1 7EH U.K.
REFERENCES Naylor CD, Basinski A, Abrams HB, Detsky AS. Clinical and population epidemiology: beyond sibling rivalry? J Clin Epidemiol 1990; 43: 607411. Sackett D, Haynes RB, Tugwell P. Clinical Epidemiology-a Basic Science for Clinical Medicine. Boston: Little Brown; 1985. Last JM (Ed). A Dictionary of Epidemiology. New York: Oxford University Press; 1988. Silman AJ, Allwright SPA. Elimination or Reduction of Diseases? Oxford: Oxford University Press; 1988.
Response
Dr Holland’s letter reminds us that the commonality between clinical and population epidemiology extends beyond the realm of tools used for research, and into the service roles of clinicians and public health practitioners. I am grateful for his comments and agree with almost all the points made, but a few clarifications are in order.
We did not actually argue that Drs Sackett, Tugwell and Haynes had contributed to the problem of “sibling rivalry” [l] by subtitling their textbook A Basic Science for Clinical Medicine [2]. Although the McMaster primer is oriented primarily to medical students and residents, this may reflect the authors’ priorities in pedagogy, or their view of clinical epidemiology,