A Contribution to the History and Philosophy of the Risk Factor Approach to Disease
Epidemiology, Chronic Diseases and the Risk Factor Approach since the 1920s: Shifts in our Concepts of Health and Disease
Cooperation Partners:Paris1 Sorbonne University, Institut d’Histoire et de Philosophie des Sciences (IHPST), CNRS
One of the main sources of contemporary issues around the definitions of health and disease is the importance of the “risk approach” to disease and of the notion of “risk factor” in medical thought and practice. This approach to diseases, introduced by epidemiologists in the middle of the twentieth century, has brought about a new kind of preventive medicine which does not seem to be related to any of the preventive public health programs of the twentieth century. Since the 1970s, preventive practices by general practitioners, such as the prescription of preventive treatment for hypertension or for hypercholesterolemia, have become common in most of the more developed countries. Prevention of cardiovascular diseases is now based on a prediction of individual risk. Such predictions have created a new and fundamental role for medicine in prevention. Moreover, they have contributed to the blurring of the demarcations between, on the one hand, public health and medicine, cure and prevention, and, on the other hand, between the normal and the pathological, the causes of a disease and the disease itself.
Indeed, the introduction of the notion of “risk factor”, which is constituted within the framework of population analysis at a statistical level but applied to individuals in clinical preventive strategies, has led to a blurring of the demarcation between population perspective and individual perspective. Correlatively, it has led to a tendency to substitute a continuous model of the relation between health and disease for the traditional dichotomous model. For most risk factors, we observe a continuous relation between the level of the risk factor and the risk of a disease. We encounter differences of degree rather than differences of kind, and it is difficult to determine a threshold below which there would be no risk of developing a disease and above which a disease would be much more probable. To define “health” as “absence of disease” is inadequate here. Under these circumstances, clinical reasoning, which necessarily requires a binary outcome (the decision to treat or not to treat), will somehow have to deal with the uncertainty and continuity of the variables of risk. Physicians no longer think in terms of presence or absence of disease, but in terms of acceptable levels of risk, and they treat risk factors in the same way as they treat the diseases themselves.
In short, the notion of risk factor is confusing and calls into question various traditional distinctions. New questions are raised concerning the definition of the pathological, and a conflict has appeared between a population-based approach and an individual-based approach. The present project aims at contributing to the clarification of this situation by developing, firstly, a historical and epistemological analysis of some of the roots of the risk factor approach to disease, and secondly, a conceptual and philosophical critical analysis of its impact on our concepts of health and disease:
- An epistemological and historical analysis of the modern epidemiological approach to diseases with a particular focus on American cardiovascular epidemiology
- Concepts of health and disease phenomena in the risk factor approach
To summarize, the aim of this project was to analyze whether, and if so, to what extent, there is an epidemiological concept of disease that would allow us to decide, or perhaps rather overcome, the ancient debate between ontological/clinical and physiological conceptions and between naturalist and normative views of health and disease phenomena. This shed light on the question whether epidemiology can create a body of knowledge about states of health that differs from that obtained in clinical and laboratory (physiological) medicine, and at the same time complement it.