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Risk Prevention in Medicine: from a Population-Based Approach to a Personalized Approach

Pierre Corvol
p. 42

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Source: La lettre, no. 34, July 2012

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1Suffice it to say that the type of diseases or conditions that affect us is evolving, with a growing prevalence of chronic diseases.

Caption: Louis Jouvet in Knock (1951) © DR

2The infectious diseases that largely determined life expectancy and mortality in previous centuries are now giving way to cancers and degenerative disorders. Along with this trend, our societies are demonstrating increasingly high expectations regarding the quality of care and the need to be shielded from the risk of disease. Some speak of the emergence of a new obsession with health which may go hand in hand with a growing refusal of pain, old age, or even death. This is the context of risk prevention in medicine demanded by our fellow citizens who want to avoid diseases and delay death at all cost.

3The seminar of the Chair of Experimental Medicine, “Risk Prevention in Medicine: from a Population-Based Approach to a Personalized Approach”, addressed so-called “mass” prevention, applied indiscriminately to an entire population, as well as targeted, personalized, customized prevention. The latter is becoming possible by means of an analysis of a given person’s own particular antecedents and characteristics, in their own environment. The shift from global prevention to personalized prevention meets the desires of both doctors and patients.

4The World Health Organization (WHO) defines prevention as all the measures aimed at preventing or reducing the number and gravity of diseases or accidents. It distinguishes three types of prevention; this seminar dealt only with primary prevention, which seeks to prevent or delay the appearance of a new disease.

5The application of prevention to an entire population is not a recent phenomenon. Smallpox ranked among the primary causes of death in the eighteenth and nineteenth centuries: Paris counted 14,000 smallpox victims in 1796, as Jennerian vaccination was in its fledgling stages. Thanks to systematic vaccination, smallpox was eradicated – a unique yet crucial example of the elimination of a disease through mass-vaccinal prevention. Another landmark example of a simple tool for large-scale prevention is the practice of asepsis through hand washing. We owe this to the Austro-Hungarian obstetrician Ignace Semmelweis, who rigorously demonstrated that this hygiene measure reduced death from puerperal fever in the maternity wards of Budapest where this procedure was implemented.

6In 1902, France saw the promulgation of a law on the protection of public health, following the occurrence of serious plague epidemics in Marseille. These epidemics motivated several gene­ral sanitary measures, and mayors were given responsibility for the difficult task of ensuring hygiene in their municipalities. Thus emerged an understanding and collective organization of medicine with detailed means, compulsory expenses and even legally prescribed penalties in cases where sanitary policy measures were not respected. This law was to thank for the prevention of epidemics, with smallpox vaccination made compulsory, and sanitary visits allowing entry right into buildings to ensure that the population was not at risk because of an insufficiently hygienic environment. Owing to this hygienist approach, success in terms of life expectancy was noteworthy. Tuberculosis, for example, had declined even before the first tuberculosis treatments appeared in the late 1940s.

7A modern epidemiology serving prevention appeared in the wake of the Second World War, with the launch of large pros­pective empirical studies. The first and most significant such study began in 1948 in Framingham, in the United States. The initial project consisted in recording the cardiovascular diseases that had newly appeared over a generation, and linking­ them to patients’ biometric and biological characte­ristics. The Framingham study, a first and a remarkable example of “explanatory” epidemiology, allowed for the identification of the main risk factors responsible for cardiovascular diseases: high blood pressure, smoking and hypercholesterolemia. It motivated the prescription of medication-based treatments for high blood pressure in the 1970s and for hypercholesterolemia in 1985, thus paving the way for major medical progress, in view of the very high prevalence of cardiovascular diseases.

8Today, it is becoming possible to personalize prevention measures for individuals, even though these measures are based on data stemming from the analysis of a population studied at a given time, in a given context. There are therefore cardiovascular risk prediction algorithms which use calculations based on factors such as age, sex, tobacco consumption, and blood pressure and cholesterol measurements. Initially based on the Framingham study in the United States, these prediction scores can be applied to our environment thanks to the studies­ carried out in France and elsewhere in Europe. They can be used, for a given patient, to calculate the probability of the occurrence of a cardiovascular condition, whether fatal or not, in the five to ten years to come, with a certain margin of error.

9A risk prevention policy at the level of a population has several aspects: vaccination prevents infectious disease epidemics and is now also applied to the prevention of certain cancers; communication campaigns stigmatize dangerous individual and collective behaviours (smoking, dietary behaviours, alcoho­lism, unprotected sex, etc.) and promote “virtuous” habits, like physical exercise or a diet rich in fruit and vege­tables. One of the major goals of prevention is to reduce ­avoidable morta­lity, such as smoking-related mortality, which still represents a third of cardiovascular deaths in France (60,000 deaths an­nually). Finally, screening campaigns allow for different conditions to be diagnosed and treated early on: chronic cardiovascular diseases, cancers, macular degeneration linked to age, etc.

10Risk prevention in medicine must continuously adapt to take into account the evolving sanitary and medical context. New infectious diseases have appeared (Aids, prion-related diseases, bird flu, to name but a few), some of which can be prevented by developing new vaccines. The prevention of cancers and chronic conditions revolves around the identification of patients’ individual characteristics: biometric, biological, genetic, medical imaging data, etc. Patients themselves can adopt preventive measures, including self-monitoring and the use of Internet (telemedicine, e-health). Validating and estimating the predictive value of new individual prevention indicators requires numerous prospective studies and therefore time and heavy funding. Thus, after the discovery of the human genome sequence in the early 2000s, it was believed for a time that we would be able to predict the risk of occurrence of a disease based on the variants of a person’s genes. The human genome sequencing gave hope of customized forecasting of the occurrence of complex diseases. Twelve years later, we must face the facts that this is not the case, and that it would be dangerous today to make a prognosis for the ten years to come. This disappointing observation does not however mean that we have not made significant progress in pharmacogenetics or in the personalized treatment of several types of diseases.

11The seminar also addressed the provocative issue of a possible extension of primary prevention of cardiovascular diseases through the medicinal treatment of a population known to be normal. “Normal and pathological” were long considered as two clearly distinct entities. Was it rightfully so from a prevention pers­pective? Perhaps not, for if we consider the correlations between the numbers of risk factors (blood pressure, cholesterolemia, etc.) and deaths from cardiovascular accidents, we observe a continuous relationship, without any threshold effect. Treating a “normal” population to prevent the occurrence of a cardiovascular accident becomes an option to consider with a person whose primary risk is, inevitably, age! Systematically treating risk factors from a certain age (55?) can be envisaged since generic medicines with a low dosage exist, which are affordable and remarkably well tolerated. This preventive strategy is particularly attractive in developing countries where the prevalence of these conditions is constantly growing. The changing intervention thresholds in cardiovascular prevention and the evolution of the economic context of medication are examples of new parameters in the cardiovascular prevention equation.

12Risk prevention in medicine is inherently multidisciplinary. It draws both on the fundamental sciences and the huma­nities and social sciences, especially economics, demo­graphy, anthropology, and sociology. Any preventive measure first involves reflection on the targeted goal, the allocated means and the strategy to adopt. It requires an estimation of the cost/benefit ratio to expect. And its implementation is ultimately an eminently political decision. The seminar adopted a multi­disciplinary approach to discuss the determinants, potential pitfalls and new possibilities of prevention which, while it is still currently based on a population approach, will shift to the individual level in years to come.

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Légende Caption: Louis Jouvet in Knock (1951) © DR
URL http://lettre-cdf.revues.org/docannexe/image/2688/img-1.png
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Référence électronique

Pierre Corvol, « Risk Prevention in Medicine: from a Population-Based Approach to a Personalized Approach », La lettre du Collège de France [En ligne], 7 | 2015, mis en ligne le 02 novembre 2015, consulté le 27 juin 2017. URL : http://lettre-cdf.revues.org/2688

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Pierre Corvol

Experimental medicine

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