The word "health" derives from Middle English helthe, meaning hale, hearty, sound in wind and limb. Dictionary definitions allude to soundness and efficient functioning and give the same meaning to financial health as to bodily health. Modern medical practice and public health are concerned about the health of individuals and populations. However, for most individuals and for many cultures, health is a philosophical and subjective concept, associated with contentment and often taken for granted when all is going well. Health in this sense is difficult to describe or define, but its absence is readily recognizable, even when replaced by minor departures from an accustomed level of health.
DEFINITIONS AND CONCEPTS OF HEALTH
In the preamble to the constitution of the World Health Organization (WHO) health is described as "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity." This description has often been criticized as being too vague. Further, it describes an ideal state rarely attained by most people, and it contains no ingredients that can be readily measured or counted, either at the individual or the population level.
Another definition, composed by specialists in preventive medicine, specifies some tangible components of health; calling it "a state characterized by anatomical, physiological, and psychological integrity; ability to perform personally valued family, work, and community roles; ability to deal with physical, biological, psychological, and social stress; a feeling of well-being; and freedom from the risk of disease and untimely death" (Stokes, Noren, and Shindell, 1982). Everything mentioned in this definition can be measured and counted at the individual and at the population level, although assessing "a feeling of well-being" may be a challenge, and "freedom from the risk of disease and untimely death" is not an achievable state.
An increasing level of interest in health promotion in the early 1980s inspired a WHO working group to compose a definition recognizing the role of individuals and communities in determining their own health status. They can be paraphrased to the extent to which an individual or a group is able to realize aspirations and satisfy needs and to change or cope with the environment. Health is a resource for everyday life, not the objective of living; it is a positive concept, emphasizing social and personal resources as well as physical capabilities (Last, ed., 2000). This definition draws attention to the need for partnerships among individuals and communities, and to the importance of protecting the integrity of the environment in the cause of promoting good health. Moreover, many aspects of this definition are measurable.
The health of humans cannot be dissociated from the health of the life-supporting ecosystems with which humans interact and are interdependent. Moreover, no matter how healthy the present generation may be, the health of future generations is dependent upon the integrity and sustainability of these ecosystems. A definition of "sustainable health" that recognizes this interconnectedness states that health is a sustainable state of equilibrium among humans and other living things that share the earth (Last, ed., 2000). The key word in this definition is "equilibrium" meaning harmony. Human beings cannot long remain healthy in an environment in which they are out of harmony with other living things, or if other living things are dead or dying as a consequence of people's actions. This is true of all life forms, from the smallest microorganisms to the largest mammals. Since the mid–twentieth century, medical professionals have been trying to "conquer" pathogenic microorganisms with antibiotics. This is a war that ultimately cannot be won because micro-organisms have very short generation times, measurable in minutes. Microorganisms can therefore adapt to the challenge of antibiotics by evolving and producing antibiotic-resistant strains much more rapidly than new antibiotics can be developed.
An alternative to antibiotics, which is perhaps insufficiently implemented, is based on the ecological concept that humans are an integral part of the global ecosystem. Immunization programs aimed at protecting people from diphtheria, tetanus, and other diseases have been very effective. The microorganisms responsible for these diseases are still there, in people's throats, in the soil, wherever is their usual habitat. But once protected by immunization, people can live in harmony with these otherwise dangerous microbes. The challenge is to develop methods that will enable humans to live in harmony with other dangerous microorganisms and insect vectors of disease. This is a more certain way to ensure long-term health for the population than the impossible goal of attempting to exterminate these other life forms. Pathogens that have no other host than humans can sometimes be eradicated, as the smallpox virus was, and as the polio virus could soon be, at least regionally if not globally; but eradication is not feasible with microorganisms that can survive out-side human hosts.
HEALTH THEORIES AND THEIR PRACTICAL APPLICATION
Beliefs about the foundations of good health are inseparable from theories of disease. Primitive beliefs about good and evil spirits; the benevolent or malevolent intervention of fate, gods, or ancestors; disease as a punishment for sin (Murdock, 1980); theories such as those of Aristotle and Galen about the balance of bodily fluids (humors) and about the effects of miasmas or "bad air" survive in the names by which we know some common diseases, including influenza, malaria, cholera, and rheumatism. A preference for holiday resorts and convalescent hospitals at the seaside or in the mountains reflects a belief in the notion that some environments are inherently healthier than others—as, indeed, abundant evidence demonstrates.
Scientists can trace the evolution of medical science in the changing nomenclature of disease. Some modern diagnostic labels indicate a precise understanding of the causal mechanisms of disease—streptococal septicemia is, literally, the poisoning of the blood by streptococcus bacteria. Some that sound impressive, such as thrombocytopenic purpura (bruising associated with a deficiency of thrombocytes, or blood platelets) reveal partial knowledge: scientists know what causes the bleeding but not what causes the deficiency of platelets. Other disease names are deservedly vague—essential hypertension confesses out ignorance about what actually causes high blood pressure.
Modern medicine and public health embrace several theories that are confirmed by abundant empirical and experimental evidence, and medical professionals have an increasingly broad and deep understanding of the ways in which health of individuals and populations can be impaired, endangered, of permanently lost. Scientists know that many diseases are caused by invading pathogenic microorganisms, which are often communicable. Some diseases are due to a disruption or imbalance among endocrine glands that secrete hormones needed to ensure efficient bodily function, some are caused by dietary deficiency of essential vitamins or minerals, and others are caused by exposure to harmful chemicals or physical insults such as ionizing radiation or excessive noise. Some diseases are due to, or strongly associated with, emotional stress. There remains a residue of important, and sometimes common, diseases and causes of disability and premature death for which there is no known cause, although effective treatments have been developed for some of theses, often through trial and error or guesswork. High blood pressure is one such disease.
The activities of public health services aim to minimize the risk of serious departures from good health. The scope and methods of medical and public health practice demonstrate the depth and breadth of current understanding of the causes of disease, disability, and premature death, and also of the causes of good health.
Many who remain fit throughout a long lifetime attribute their good health (often incorrectly) to their behavior; whether it be to an ascetic or hedonistic way of life, to abstaining from (or indulging in) alcohol or tobacco, to vigorous exercise, or to leading a quiet, sedentary life. Some credit their parents or genetic heritage—certainly an important determinant of longevity—along with many environmental and behavioral factors. In fact, the causes of good health are as diverse and complex as the causes of disease.
Even literate, well-educated people sometimes have misguided views about what makes or keeps them healthy, often believing that regular daily exercise, regular bowel movements, or a specific dietary regime will alone suffice to preserve their good health. The Nobel laureate Linus Pauling believed that massive daily doses of Vitamin C preserved his health. Those who are less well educated and more gullible are easy prey to hucksters who purvey all manner of dubious nostrums to prolong life, enhance vitality or virility, promote fitness, and eliminate ailments ranging from halitosis and body odor to failing sexual potency and even cancer and heart disease.
Modern approaches to health education and health promotion make use of the Health Belief Model along with several other theoretical constructs to predict health-related behavior. These are based on assumptions derived from empirical studies of how people perceive their health and their understanding of what has to be done to preserve and protect their own health, or that of their children.
OBJECTIVE AND SUBJECTIVE PERCEPTIONS OF HEALTH
A well-trained physician, or an observant member of a family, can often tell at a glance that someone is unwell. There are obvious signs—pallor, sweating, unsteady gait, a bone-shaking cough. The converse is more challenging. Someone who appears to be outwardly perfectly fit—hale and hearty, sound in wind and limb—may harbor an early cancer that is eating away at a vital organ, or, when asked the right questions may reveal a potential mental health problem, though there is no physical evidence of a departure from excellent health. Health has many dimensions, and each must be assessed and measured on some sort of scale. This is what physicians do when conducting a routine medical history and physical examination, which includes various laboratory tests. The results of such an examination have a range of values that usually follow a normal distribution, and for many of these the decision that a particular value lies within or outside the range of normal is rather arbitrary, although it is based on empirical experience. For example, experience and follow-up of many sets of observations allow us to agree on what level of systolic and diastolic blood pressure give grounds for a confident recommendation that treatment is needed to reduce an excessively high pressure that could lead to a stroke or heart attack.
Conversely, many severely disabled people can function efficiently and cheerfully within their limited capacity—paraplegics can perform with consummate speed and skill in road races in wheelchairs, and blind people can play chess and swim in competitive tournaments. The theoretical physicist Stephen Hawking, described in his book, A Brief History of Time (1988), the full and productive life he leads, though he is profoundly disabled physically by amyotrophic lateral sclerosis (Lou Gehrig's disease). Physical, mental, and emotional health are clearly three different dimensions of health.
Determinants of Health. Both individual and population health are determined by physical, biological, behavioral, social, and cultural factors. First among the physical factors is the radiant energy of the sun, which is ultimately essential for all life on earth. In Airs, Waters, and Places, Hippocrates identified climate, environmental topography, and aspects of behavior as determinants of health. Climate is assuming greater importance than hitherto due to the climate changes caused by increasing industrialization and energy consumption. Environmentally, the presence or absence of trace elements in the soil or water, such as fluorides to toughen dental enamel, iodine to stimulate the thyroid gland, and lead compounds that damage the developing brain, act to enhance or impair our health.
Biological determinants of health are inherent or acquired. Genetic heritage is a contributing factor to longevity, and to susceptibility or resistance to a wide range of diseases that include the pathogenic microorganisms responsible for some of the great plagues that have afflicted humans for millennia. Molecular geneticists have demonstrated that the interaction of human communities with the plague bacillus, the influenza and smallpox viruses, the malaria parasite, and with several other microorganisms, played a role in determining the differentiation and distribution of early races of humans in Africa and Asia. On a much shorter time scale, pathogenic microorganisms may be the most important biological determinants of health and disease. Immunity or resistance to pathogens is a very important determinant of good health. Immunity is enhanced by prior exposure, or by maternal exposure in the case of newborn infants, who acquire maternal (passive) immunity to some infections before they are born, and have it reinforced after birth by antibodies in breast milk. Routine immunization of infants and small children protects them from harm by many common and formerly dangerous pathogens including those that cause diphtheria, tetanus, measles, poliomyelitis, and whooping cough. Nutritional status is another important influence on resistance to infection. Individuals and populations are most vulnerable when they are malnourished or starved, which is why plagues often accompany famines.
Behavioral determinants have been much studied. An association of certain diseases with particular personality types has been observed empirically for centuries. An irascible temperament, for example, has been linked to occurrence of strokes, and an association has been demonstrated between high risk of coronary heart disease and a type A personality, marked by forceful and aggressive behavior. Research on mind-body interactions, which unites the disciplines of psychology, neurology, and immunology, made great progress in the last quarter of the twentieth century and began to clarify and explain these relationships.
Social factors that influence or determine health are also complex. There is epidemiologic evidence that good health is determined at least in part by social connectedness. Persons who have many and frequent interactions with other family members and with a network of friends have a more favorable health experience in many ways than those who are socially isolated, live alone, are estranged from their family, and have little or no family and social support systems. It is difficult however, to unravel social connectedness and personality factors that may encourage gregariousness or a solitary way of life. Position in the social hierarchy plays a role. Michael Marmot, a professor at University College in London, and his colleagues studied British civil servants, showing that top managers lead healthier lives than middle managers, who in turn are healthier than semi-skilled and unskilled clerical workers. Social networks and support systems, and social positions, are in part determined by factors beyond the control of individuals. While they are interrelated with personality factors, they are very complex and not well understood.
Studies have shown that economic conditions dramatically effect health and longevity. A consistently strong relationship has been demonstrated between income levels and health status in every country where the relationship has been examined. Many interactions between social, economic, and cultural factors also help to determine or influence community health.
Culture is defined as the set of customs, traditions, values, intellectual, and artistic qualities, and religious beliefs that distinguish one social group or nation from another. Culture influences behavior through customs such as use of or abstention from meat, alcohol, and tobacco; the practice of rituals such as circumcision; marital customs such as the prevailing age at which women marry; attitudes toward family size, childbearing, and child rearing; personal hygiene; disposal of the dead; and much else. People's values may be the most significant component of culture that affects behavior and through behavior, health. For example, since the late nineteenth century, an understanding of the importance of personal hygiene has become part of the value system of many cultures. In the late twentieth century, values in many nations shifted towards a rejection of tobacco smoking as a socially acceptable custom. In the 1960s, the oral contraceptive pill contributed to the sexually liberated values and behavior that encouraged casual promiscuity, and which was only partially overshadowed by the threat of infection with HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome) in the 1980s and later.
PREREQUISITES FOR HEALTH
Another way to consider conditions required for people's health to flourish was outlined by working groups of the World Health Organization Regional Office for Europe in the 1980s, during the development of targets to be met in order to achieve Health for All, a program conceived with the goal of assuring that essential health care is accessible to everyone through organized programs of health promotion. The prerequisites for health were identified as: freedom from the fear of war, equal opportunity for all, satisfaction of basic needs (food, education, clean water and sanitation, decent housing), secure work, a useful social role, and political will and public support. All these are embodied in one way or another in the determinants of health outlined above, but when expressed as they were by the WHO working groups, the relevance of human values to achievement of good health becomes more explicit. Ultimately, values may matter more than anything else in influencing health.
HEALTH PROMOTION AND HEALTH MAINTENANCE
The basic goals of health promotion and health maintenance are a safe environment, enhanced immunity, sensible behavior, good nutrition, well-born children, and prudent health care. Each of these merits a brief discussion.
Safe Environment. Among the fundamental requirements for good health are clean air, safe water, land free from toxic substances, and shelter that protects people against the elements. The term "filth diseases" coined in the mid–nineteenth century, summarizes many life-shortening environmental hazards that prevailed at that time. Unpolluted water, sanitary disposal of human wastes, and improved housing conditions transformed overall health by the end of the nineteenth century. Access to food and resources essential for survival, as well as freedom from threat of war, persecution, and discrimination, are included in the European Charter for Health Promotion. A high proportion of the world's people are in want of these essential requirements for good health.
Enhanced Immunity. Next in importance to the provision of pure water supplies and sanitary disposal of human waste is the protection of infants and children against lethal and crippling infectious diseases. By the middle of the twentieth century, immunization campaigns had virtually wiped out diphtheria, tetanus, and whooping cough. Smallpox was eradicated worldwide by 1980. Development in virusvaccines in the second half of the twentieth century added poliomyelitis, measles, rubella, and mumps, to the list of diseases preventable through vaccination. This list includes other dangerous diseases that are rare in Western industrial nations, including typhoid, typhus, and yellow fever.
Sensible Behavior. The way people behave influences their health in many ways, and behaving sensibly is an obvious requirement for good health. Health-related behavior is influenced by our values, which are determined by upbringing, by example, by experience, by the company one keeps, by the persuasive power of advertising (often a force of behavior that can harm health), and by effective health education. These influences affect everyone—especially impressionable children—and lead to good or poor health, depending on the predominance of sensible or risk-taking behaviors that result.
Good Nutrition. A balanced diet comprises a mixture of the main varieties of nutriments (protein, carbohydrates, fats, minerals, and vitamins). For many reasons, not everyone has easy access to or incentives to eat a balanced diet. Some cannot afford it, others are ignorant of what kinds of food are good for them and what kinds are not; many are attracted by the advertising, convenience, and low cost of junk foods. Nevertheless, those who eat a well-balanced diet are healthier than those who do not.
Well-Born Children. By this term we mean children who are free from genetic defects, safely and easily born to healthy mothers after a pregnancy of normal duration, and nurtured securely to ensure that they pass developmental milestones in a timely manner so they grow up fit and strong. A great many characteristics are summarized in that statement, and are discussed elsewhere in this encyclopedia.
Prudent Health Care. It has been said that, until about 1930, the average patient with the average disease consulting the average physician had a less than 50 percent chance of benefiting from the encounter. In some respects the situation has greatly improved since then, but doctors even now inadvertently harm some whom they attempt to help, and hospitals remain dangerous places where patients are at risk of infection by other patients and contaminated instruments, invasive procedures can go wrong, and medications can be administered to the wrong patient or given in wrong dosages.
HEALTH INDICATORS
The health of potential military recruits and applicants for life insurance is assessed by their past history of illness and harmful behavior (e.g., smoking), and by a physical examination that includes blood pressure, tests of exercise tolerance, and other measures. Similar methods can be used to assess the health of a nation. The physical examinations of military conscripts early in the twentieth century provided evidence of the poor health of the British working classes, and which in turn motivated the government to introduce the first tax-supported medical services. In the United States, the National Health Surveys provide information about the health status of Americans (such as the increasingly prevalent obesity among young people). But this is a costly way to assess a nation's health. Traditionally, health care professionals have relied on summary statistics, especially life expectancy, which is derived from the age distribution of the population as determined by a national census. Life expectancy at birth is particularly sensitive to infant mortality, which is another widely used indicator of a nation's level of health.
More sensitive indicators take into account the available evidence on commonly occurring disabling diseases to derive summary statistics such as disability-adjusted life years. Health measurement scales are more elaborate derivatives of disability-based health indicators. These require the use of questionnaires, interviews, and sometimes physical examination of individuals to derive a numerical score for particular aspects of health such as an ability to climb stairs, shop for food, prepare meals, get dressed unaided, or drive a car. Standardized interviews can also be used to derive a numerical score for aspects of mental health, social interaction with others, and employability. When all available health indicators are complied, various conclusions can be drawn. They show, for example, that Japan, Australia, Sweden, the Netherlands, and Canada are among the world's healthiest nations; while Sierra Leone, Mozambique, and Malawi are in many respects the least healthy. The United States is among the top twenty nations according to some indicators, and among the top twenty-five according to others. But no nation has a monopoly on indicators of good health. If athletic prowess is an indicator, African Americans consistently outperform all others in sprints, while Africans from Kenya outperform all others in middle- and long-distance running. Some small nations in the mountainous Caucasus region between the Caspian Sea and the Black Sea, in the
Table 1
The top 25 and the bottom 25 nations ranked according to Disability-Adjusted Life Expectancy (DALE)
foothills of Mount Ararat, are famous for many authenticated cases of extreme longevity, and they may have the world's highest proportion of persons surviving to ages over one hundred. Yet these same nations have relatively high infant and childhood mortality rates, as well as high death rates from causes associated with violence.
Determining which nations are healthy depends on which health indicators are looked at. The Netherlands, for example, ranks at the top using indicators of health quality—literacy levels, low incidence of abortion and unwanted pregnancy, low incidence rates of impairments, disabilities, and handicaps—though other countries may rank higher in terms of longevity and other indicators.
Table 1 shows the ranking of various nations based on years of healthy life expectancy or disability-adjusted life years, the age to which on average people are expected to live in good health. This number is reached by subtracting the average years of ill health from the overall life expectancy. The top nations are Japan, Australia, and France; the bottom three are Malawi, Niger, and Sierra Leone. The United States is twenty-fourth on this list, though it is the richest nation on earth in terms of economic indicators. The poorest fifth of residents in the United States have a healthy life expectancy of just fifty-five years, compared to seventy years for the nation as a whole. Clearly there is room for considerable improvement.
CONCLUSION
Health is clearly a complex, multidimensional concept. Personal or individual health is largely subjective. It is possible to be physically robust, to be "the picture of good health," and yet have serious mental or emotional impairment. Conversely, an individual can be profoundly disabled physically yet have an intact mind and be emotionally well-adjusted. So while many facets of health can be identified, the assessment or measurement of individual health must take them all into account. Economists can derive a single number—the net worth or gross domestic product—as a measure of the economic status of an individual or a nation. But there is no comparable one-dimensional measurement scale for the health of an individual, much less a nation. At best, public health professionals can create community or national profiles using crude health indicators like life expectancy; infant mortality rates; death or sickness rates from specific causes like cancer, heart disease, suicide, and homicide; or surrogate measurements such as use of drugs, (prescribed or over-the-counter) and spells of hospital care.
Health is, ultimately, poorly defined and difficult to measure, despite impressive efforts by epidemiologists, vital statisticians, social scientists, and political economists. The dramatic differences in levels of health among the nations of the world only challenge public health professionals to pursue global health standards.
At the beginning of the twenty-first century the principal causes of premature death and departures from good health were violence, including violent armed conflict; smoking-related disease; automobile accidents; and overindulgence in high-calorie foods that are ill-suited to modern, sedentary lifestyles. All of these are ultimately associated with human behavior, which is greatly determined by values. Only by adopting values that support a healthy lifestyle can people improve their overall health.
Abelin, T.; Brzezinski, Z. J.; and Carstairs, V. D. L., eds. (1987). Measurement in Health Promotion and Protection. Copenhagen: World Health Organization.
Dubos, R. (1959). Mirage of Health. London: Allen and Unwin.
Helman, C. (1990). Culture, Health, and Illness, 2nd edition. Oxford: Butterworth-Heinemann.
King, M. (1990). "Health Is a Sustainable State." Lancet 336:664–667.
Last, J. M. (1997). Public Health and Human Ecology, 2nd edition. Stamford, CT: Appleton and Lange.
Last, J. M., ed. (2000). Dictionary of Epidemiology, 4th edition. New York: Oxford University Press.
Marmot, M., and Wilkinson, R. G., eds. (1999). Determinants of Health. Oxford: Oxford University Press.
Murdock, G. P. (1980). Theories of Illness. Pittsburgh, PA: Pittsburgh University Press.
Stokes, J. III; Noren, J. J.; and Shindell, S. (1982). "Definitions of Terms and Concepts Applicable to Clinical Preventive Medicine." Journal of Community Health 8:33–41.
World Health Organization (1948). Constitution and Charter. Geneva: Author.
—— (1978). Primary Health Care. Geneva: Author.
—— (1985). Targets for Health for All. Copenhagen: Author.
—— (1986). "Ottawa Charter for Health Promotion." Canada Journal of Public Health 77:425–430.
