The term "prevention" encompasses the philosophy, credo, programs, and practices that aim to defer or eliminate diseases, disability, and other forms of human suffering. Additional discussions of disease prevention, the stages of prevention (primary, secondary, and tertiary) and the issues of clinical prevention in the setting of personal health services can be found elsewhere in this encyclopedia. The notion of prevention in populations has a long history of discovering and eliminating the causes of disease. For example, in the 1840s Hungarian physician Ignaz Phillipp Semmelweis reduced the rates of puerperal sepsis among pregnant women through attendant hand washing. In the 1850s, British physician John Snow helped abort an outbreak of cholera in London that was due to a contaminated water supply. The gradual assumption of sanitary practices in public health and preventive activities in clinical practice has been in place for a long time and is increasing, although always challenging and incomplete.
THE CONTEXT OF PREVENTION
The causes of disease and disability are gradually being discovered and either removed or ameliorated due to scientific advances as well as clinical and preventive interventions. While there are many measures of health, one of the most basic, mortality rates, improved at an unprecedented rate during the twentieth century, providing a strong basis for optimism that new preventives and treatments will continue to enhance health status. However, many diseases and conditions and other causes of human suffering are of unknown or incompletely understood causes. While striving to optimize health status and minimize dysfunction and disability within populations and individuals, it is likely that there will always be a health and functional burden on societies. There are several reasons for this including: uncontrollable acts of nature, such as meteorological and climatic catastrophes; war and other forms of interpersonal violence; unanticipated adverse effects of advancing technology or occupational exposures; adverse effects of health interventions (even if the net health benefit is positive); the constant evolution of infectious organisms; naturally occurring errors in function, which will inevitably occur among complex biological systems, even in the absence of known environmental stimuli; the uncontrollability of individual behavior; and the unintended consequences of health-giving interventions, such as the development of resistance to antibiotics that once successfully cured a wide variety of life-threatening infections.
While public health and the medical sciences continue to develop new preventive and curative modalities, there are ecological factors and forces intimately related to diminished population and individual health that could be addressed even in the absence of clear causal or pathogenetic mechanisms. One of the most important is the close relation between socioeconomic status and health. Both within and among populations, those with higher levels of affluence and various social and economic resources in general have higher levels of health by almost all available indices. One particularly common finding is the relation between income inequality and mortality. There may be several explanations for the generally strong association between income levels and subsequent mortality: (1) higher income levels are a measure of a safer physical environment, including occupational exposures and the general environment; (2) higher income purchases more effective personal and family health services; (3) higher income and wealth levels are literal markers of social status, with lower levels being characterized by increased stress from social oppression and distrust; and (4) income and wealth are markers of increased education and healthy behaviors. It is also possible that the association occurs because individuals with physical or mental conditions have a lesser ability to earn higher levels of income and accumulate wealth.
Even in the absence of full explanations for the income-disease association, some possible solutions may be available, including social policies that limit large levels of income inequality, and expenditures on economic development, which might improve health status secondarily as well as increase access to personal health services. However, the evidence for the effects of these social and economic policies is incomplete, and additional intervention studies are needed.
Despite the presence of global factors that appear to be important forces for disease causation, and the likelihood that disease and disability will quite likely continue to be public health and clinical challenges, a substantial amount is known about the causes of many conditions, and preventive interventions are available to lessen, if not eliminate, their public health burden. When considering disease prevention, it is axiomatic that most important clinical illnesses have multiple causes. For example, deaths from certain viral infections may be caused by the lack of immunization facilities, the failure to handle and administer vaccines properly, household crowding, inadequate nutrition and lack of knowledge to seek early care when the infection appears, as well as biologic variability in susceptibility. Coronary artery disease is caused by several factors, including genetic contributions, high fat diets, cigarette smoking, elevated blood cholesterol levels, and inadequate exercise: Preventive action aimed at several of these factors should have a salient effect. Thus, interventions at several critical points in disease causation—clinical, behavioral, policy, and educational—may all decrease morbidity and mortality. In many instances, multifaceted interventions may provide the best levels of prevention rather than any single approach. A corollary principle is that a preventive intervention at one locus may help prevent several conditions. An effective clinical smoking-prevention program will decrease the risk of several heart and lung diseases.
ROBERT B. WALLACE, The Gale Group Inc., Macmillan Reference USA, New York,