Genetics and Health Care: A Paradigm Shift

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GENETICS AND HEALTH CARE: A PARADIGM SHIFT P. A. BAIRD* This article is about health care in the future—some of the things addressed are quite a few years in the future, some are here now, and others are coming very fast. I want to put my remarks in the context of my conviction that as a society we need to change our view of disease as an outside enemy—and find a new way of thinking about illness. Over the last century or so, the living conditions of human populations in developed countries have altered markedly, with resulting dramatic changes in health, largely owing to progress in nutrition and hygiene . Measures of population health such as life expectancy rose rapidly in the early decades of this century, with far fewer people dying prematurely from malnutrition or infectious diseases such as TB and cholera. A larger proportion of the population now lives to approach the normal biological life span of humans, which is probably in the 85-95year range [I]. The age structure of the population has changed from one that has a preponderance of young people under 30 to a distribution that includes more people in their middle years and older. The benefits of public health and good nutrition in Western societies have led to a remarkable decrease in those diseases with a primarily external cause. Perhaps because of this success, most physicians and investigators have perceived that deleterious influences on human health are of two kinds: either a deficiency of a basic resource such as food or vitamins, or exposure to hazards that may be either natural (such as parasites, bacteria, or viruses) or man-made (such as smoking, war, environmental pollutants [2]). Genetics is now showing that this view of the determinants ofhealth as being external is too simplistic. It neglects a major determinant of disease —an internal one. Far from being a rare cause of disease, genetic The author expresses gratitude for helpful comments and criticism to J. Friedman and F. Rolleston. * Department of Medical Genetics, University of British Columbia, Room 226, 6174 University Boulevard, Vancouver, British Columbia V6T 1W5.© 1990 by The University of Chicago. All rights reserved. 003 1 -5982/90/3302-066910 1 .00 Perspectives in Biology and Medicine, 33, 2 ¦ Winter 1990 \ 203 factors are a very important determinant of health or illness in developed countries. The most widely held model of disease says that disease has clinical manifestations [3], These manifestations are classified to allow us to diagnose disease, and appropriate treatment is dependent on making an accurate diagnosis. This is the concern and focus of most of today's practice of medicine. We seem to treat manifestations and pathogenesis, and pay less attention to causes, of disease. Less attention in particular has been given in our thinking to the internal cause of disease, especially with regard to common disorders [4]. Genetic factors in human disease were initially identified through the study of unusual and rare variants, for example, phenylketonuria, cystic fibrosis, or Huntington disease, in all of which there is a clear internal cause. In these uncommon diseases, a defect in a single gene makes the patient unable to carry out metabolic mechanisms that allow normal functioning. We now know of about 4,000 different single-gene disorders in humans, each one relatively rare but in total a significant burden on health. Most important, though, diseases now common in Western populations do not have either only an external cause, such as vitamin deficiency, or only an internal cause, such as phenylketonuria. Most common diseases are multifactorial—they are due to a combination of internal and external causes; due to interactions between the individual's genetic makeup (predisposition) and his or her particular experience [5]. We need to shift our model of how illness is determined to take this into account. The relative contribution of genetic causes to all causes of disease in our population has likely increased markedly in this century for many disorders. For example, in the early years of the century the infant mortality rate in the United States was about 150 per 1,000 live births [6]. It is estimated that about five of these 150 deaths...

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