Biostatistics is the science used to quantify relationships observed in public health and medicine. Through the correct application of biostatistical techniques, public health professionals can test and quantify the magnitude of the relationship of a factor or factors to the health of the community.
Advances in epidemiological methodology have been accompanied by rapid progress in biostatistics, particularly the development of computer technology. Through its application, biostatisticians have developed multivariate techniques to sort out the independent relationship of multiple factors to disease occurrence while simultaneously observing the relationship of these variables to each other. Sophisticated techniques for the analysis of events in relation to time are enhancing the value of the cohort study design. Because the computer can process massive amounts of information rapidly, it has been possible to develop and test mathematical models that describe hypothetical relationships and disease outcomes based on a variety of assumptions. The degree to which the actual occurrence of disease matches the model confirms or refutes these relationships. These models can be used to predict the future course of disease both in the individual and in the community. Both are useful for public health administrators responsible for allocation of scarce resources.
These new statistical techniques have been used to determine the strength of a relationship between a suspected risk factor and disease occurrence or causation, and to determine the efficacy of preventive strategies such as vaccines and health education, the level of efficacy of drugs through clinical trials, and the future course of epidemics. Through further development of biostatistical strategies and innovative computer methodology, the potential of statistics to contribute to public health will be even greater.
Biological and physical sciences
The laboratory sciences have long played an essential role in public health. Many of the new advances leading to the control of infectious diseases depend upon microbiology to provide new techniques to identify and isolate disease agents, to describe relevant variations within a group of agents (e.g. polio types 1, 2, and 3), to describe host variations in susceptibility to disease, and to identify markers of prior infection or exposure. The rapid expansion of vaccines to prevent viral diseases reflects new procedures for isolating viruses using cell cultivation techniques that were developed in the late 1930s. These cell culture techniques facilitated the manufacture of live vaccines using attenuated viruses, that is, viruses that have lost their virulence characteristics for humans but not their capacity for stimulating immunity. Recently, microbiologists have fragmented disease agents into specific components and selected those that are responsible for the protective immune response. Vaccines are now also being developed that utilize genetic recombination and synthetic peptide chains (NIAID 2000). It is likely that within the next few years vaccines based on DNA will become a reality. New techniques have been developed for identifying levels of viral DNA and RNA in cells and serum. These techniques can be used to provide new insights into the early stages in the infective process, to identify chronic diseases that have a viral aetiology, and to guide therapy.
Startling as these recent developments in microbiology and immunology have been, equally important contributions to public health continue to come from the laboratory sciences of chemistry, biochemistry, and engineering. These disciplines provide information about the levels of pollutants in the air, water, and soil which is used by epidemiologists to determine their health effects. The studies of the chemical interactions of primary pollutants in the atmosphere led to the discovery that the products of these interactions, such as photochemical oxidants, can cause permanent compromise of lung function. Physical scientists continue to develop monitors that can measure specific pollutant exposures even at the personal level. Knowledge of chemical interactions has also led to the development of catalytic converters which have played a major role in reducing pollutant levels due to vehicle exhaust emissions in urban areas. Further advances in the physical sciences can be expected to provide a more healthful environment in the future.
Advances in the laboratory sciences can be rapidly translated into new techniques for identifying infection and disease, as well as environmental and occupational hazards. For the epidemiologist they provide tools to identify and measure disease agents and knowledge which leads to the development of testable hypotheses. Thus, these new advances often lead to new techniques and strategies for intervention and control of threats to the public health.
Behavioural and social sciences
In addition to their influence on choice of exercise, levels of personal hygiene, eating patterns, and alcohol consumption in disease occurrence, behavioural factors also determine the response to illness, particularly to subtle manifestations of disease. Thus, they significantly affect the ability of the individual to live in a healthy way and to respond to disease. The role of the behavioural and social sciences (including psychology, sociology, and anthropology) in public health is therefore increasing as the nature of disease problems is changing. Experience with HIV/AIDS as well as cardiovascular disease and cancer over the past few years dramatically illustrates the need for changing types of behaviour that promote disease occurrence (Fauci 1996; Mann and Tarantoloa 1996).
Behavioural science techniques have proved valuable in understanding important influences on health. Social science, particularly its relationship to statistics in developing survey methodology and its increasing application to smaller population groups, for example, has greatly enhanced our capacity to discriminate the possible connections of behaviour and ecological factors to disease and thus to discern trends that are highly important to public health. Psychological investigations of people’s knowledge and attitudes yield insight into the habitual and lifestyle practices that are related to health and often suggest ways of promoting health. Sociological investigation of group processes that determine a community’s norms and values, and adherence to them, likewise leads to an understanding of how people behave and how they can be influenced to follow a healthy lifestyle. Anthropology elucidates the cultural traditions that affect what people do in everyday life and suggests approaches to health promotion specific to various cultural groups.
Within the field of public health, health education draws upon these disciplines to develop effective techniques for cultivating health-promoting behaviour (Green and Kreueter 1998). As emphasized above, the social milieu largely determines the choices that people make. Economic and other social conditions of life profoundly impact what people do about health-related actions. Lifestyle does not consist of behaviour elements selected by individuals in a void but depends upon their life circumstances. Hence public health must be concerned with the social conditions in which people live and direct substantial effort towards their improvement on behalf of health. The social sciences provide knowledge that guides analytic effort, in that regard, as well as for organizing and managing appropriate interventions; and they therefore contribute to formulating and implementing policy for public health.
Demography, vital statistics, and health information
Demography delineates the nature of populations, focusing on trends such as growth in their various segments, i.e. the excess of births over deaths, and immigration over emigration. Public health statistics are concerned with information about the health of populations. Both fields are devoted to satisfying social concerns about people. Mutual interest in factors such as those determining fertility illustrates the continuing interrelationships of public health and demography.
John Graunt is commonly considered the father of vital statistics because of his early studies of the Bills of Mortality in London and a parish town in Hampshire. He collected and examined the birth and death records maintained by parish clerks from 1603 to 1662 (Graunt 1662). From that work he drew important inferences about the population and its health. He analysed mortality, including infant mortality, seasonal variation of deaths, and longevity, as well as fertility and the excess of male births. His studies laid the groundwork for what has become vital statistics, which now include:
births and the rates of their occurrence in various segments of the population;
fertility, i.e. the ratio of births to women aged 15 to 49 years;
mortality, including deaths amongst infants and in subsequent ages, as well as trends, specific causes, and determinants of deaths;
Information about health may be obtained through aggregated data from vital statistics, surveys, disease reporting, and disease registries as well as demographic statistics. Computer technology facilitates analysis of such data in relation to the characteristics of people affected. In addition, information from other sources can be linked to the occurrence of health events, thus providing additional information about factors in these events.
Data concerning non-lethal diseases are more difficult to obtain than the birth and death information that must be recorded by law. In the United States, the Centers for Disease Control and Prevention publishes a Morbidity and Mortality Weekly Report, which contains information on certain diseases, obtained through reporting from local health departments. Hospital discharge abstracts and summaries provide further information. Special surveys for specific diseases or factors affecting health may be carried out, in addition to ongoing national health surveys administered to a probability sample of the population. Cancer registries in several countries provide information about changing trends in cancer occurrence, mortality, treatment effectiveness, and duration of survival. Comparable data registries are also being developed for diabetes, coronary heart disease, congenital malformations, and other chronic diseases.
Programmatic scope of public health
Success in achieving the WHO’s objective of eradicating smallpox throughout the world and, more recently, its initiative to eradicate poliomyelitis by 2005 (which has already been accomplished in the western hemisphere), have inspired other efforts to set and popularize explicit goals in public health (WHO 2000). For example, in 1980 the United States Department of Health and Human Services established specific objectives for 1990 in various health domains and a data collection and publication process to track progress in meeting the objectives (US DHHS 1980). It also delineated the measures necessary to reach those objectives. Based on experience with that venture, the agency set new goals in priority areas for the year 2000 (US DHHS 1991). For some specific objectives the trends have been on track, but for others, such as obesity, the trend was in the wrong direction. New goals for health priorities are now being formulated for the year 2010 (Table 6) (Institute of Medicine 1999).
Table 6 Core list of candidate leading health indicators for Healthy People 2010
Prevention of disease and promotion of health
The ultimate goal of public health has always been and remains the prevention of disease and the promotion of health in communities. Attention to quality of life is also growing, and represents a more positive goal than the traditional target of disease control in the health field (Breslow 1999). Although great strides have been made towards that goal, many conditions still cause considerable unnecessary deterioration in the quality of life as well as in disability and premature death. Furthermore, many people in both the developed and the developing world have not yet benefited from the public health achievements of the twentieth century. A major goal of public health in the developed countries in the future, therefore, will remain the prevention of diseases such as cancer, heart disease, trauma, and AIDS, which are currently responsible for most premature mortality and diminished quality of life. Achieving that goal requires assurance that public health advances reach those groups of people still suffering heavily from morbidity and mortality that can be avoided using current knowledge and technology. These include the poor and those not yet adequately integrated into the mainstream of society. In developing countries, reduction of infectious diseases and malnutrition often still must take priority, but increasingly, reduction of chronic diseases, accidents and trauma, and environmental threats to health are becoming goals there as well.
Prevention can be achieved through:
emphasizing preventive aspects of medical care, such as immunizations and screening for selected conditions;
health education and behavioural modification, including social influences on these aspects of health;
control of the environment for health;
cultivating political will for public health initiatives.
Beginning with Bismarck, the Western nations have generally provided medical care of varying kinds and degree as a social benefit to industrialized workers. In most countries care has also been extended to others, particularly to families of workers, the elderly, and the poor. The British National Health Service, for example, covers the whole population. Conversely, the United States relies mainly on private arrangements for employed people, and large-scale governmental assistance for health-care services goes only to the elderly and the poor, while one-sixth of the population has no coverage.
Medical care can be examined from several perspectives: medical and economic, for example, as well as from the standpoint of public health. The medical profession, reflecting both the centuries-old tradition of healing, as well as recent advances in medical science, looks upon medical care as the principal means to relieve suffering and restore health in individuals. Economists view medical care in terms of its cost and therefore are concerned about the increasingly large expenditures for it. Public health considers medical care to be one means of protecting and improving the health of people, but also is vigilant about its cost and financing, especially in so far as that constitutes a barrier to health care for some groups. Public health’s focus on medical care emphasizes its potential for enhancing a community’s health, with its cost a consideration in the same sense that environmental protection raises financial issues. Public health usually does not assume responsibility for the actual delivery of health care to the individual, but is concerned with the quality, access, and equity of the care that is provided.
Provision of medical services is usually determined in a specific country by cultural and traditional patterns, although these medical service patterns are constantly evolving. Thus, in the United Kingdom the individual general practitioner with a panel of patients comprises the predominant care module, with referral to the hospital consultant as necessary. However, a current trend is for general practitioners to work within group practice prepayment plans; for example, in the United States the former lifelong doctor–patient relationship is often replaced by health centres or clinics where the patient may be seen by a primary care doctor, by some specialists, such as paediatricians, general internists, or obstetricians, who see patients only during certain limited periods of their lives, and, to a growing extent, by free-standing emergency medical services. The number and type of various medical service arrangements and payment methods are rapidly expanding in the United States.
Public health relies upon doctors primarily to achieve preventive medical care. Thus, public health agencies have organized immunization activities and often maternal and child health services both through existing sources of medical care, and, where necessary, through direct provision of these services. In recent decades these efforts have contributed to spectacular achievements in control of communicable disease, for example the eradication of smallpox and the extensive control of poliomyelitis.
Curative services, however, generally receive funding priority over preventive services on the grounds of urgency. Most doctors and medical care agencies adhere to what may be termed the complaint–response system of medicine; patients are encouraged to recognize and bring their health complaints to the doctor, whose response is to diagnose and treat any illness that may be present. Prevention, if advocated at all, is usually a minor consideration.
A new system of medical care that gives priority to promoting health and preventing disease has been slowly emerging. The health of individuals is monitored through periodic appraisal geared to age and other factors that determine both current and future prospects of health. Thus, infant care concentrates on growth, appearance of defects, immunization status, and any necessary corrective action to assure the healthiest possible development. When a person has reached 50 years of age, the focus shifts to blood pressure, weight-to-height ratio, blood sugar, blood cholesterol, cancer detection, cigarette and alcohol consumption, and other physical and behavioural characteristics. Many industrial leaders in the United States have started to provide health risk assessment and health counselling services for their employees. Arrangement for these services at or in connection with work is one of the fastest growing aspects of medical care in the United States (Fielding 1989).
While medical care services have absorbed a rapidly increasing proportion of total expenditures for all goods and services in some developed nations, the developing world has not had the resources to commit to such an effort. Vast numbers of people can thus receive only the most elementary medical services, if any. Furthermore, as medical education advances in the developing nations, a substantial number of doctors seek training in the high-tech training centres around the world. Those returning to their native countries then try to introduce the procedures they have learned, but these are pertinent and available mainly to the élite in their societies. That circumstance aggravates the tendency to spend the money largely on curative services rather than on the huge backlog of needed preventive services in the developing world. Use of community health workers, i.e. people recruited from the communities themselves and trained to promote health, as developed in several countries, may help to alleviate the problem.
In addition to the relative emphasis that should, worldwide, be accorded preventive vis-à-vis curative efforts, several other issues currently affect the public health approach to medical care. Previously many procedures and drugs have come into widespread use without sufficient consideration of their effectiveness. Initiatives are now underway, for example, by the Medical Research Council and the Departments of Health and Social Security in the United Kingdom, and the Congressional Office of Technology Assessment in the United States, to establish better systems for evaluating the effectiveness of medical technologies, including drug regimens, as well as to shorten the interval between the development of a drug and its licensing.
These initiatives reflect concern about the rapidly rising cost of medical care in the Western nations and about features with questionable, or even negative, relevance to health. Another rising issue is the efficiency of medical service, that is, how the best possible quality of medical care be provided within a given amount of resources. New facilities for ‘ambulatory surgery’, for example, make it possible to carry out many procedures without the extra expense entailed in admission to a hospital. Organizing medical personnel into groups, as well as providing incentives to personnel, offer possibilities for increasing the productivity of medical services. However, another cost-related issue is the extent to which medical resources should be used for highly expensive procedures and devices, such as heart replacement, that benefit only a few people at great expense. Recently, managed care organizations, which are private for-profit organizations, have become popular as a cost-effective strategy for providing care. Managed care organizations emphasize primary care, but the primary care doctor and a review board in them also act as the gatekeeper for seeing specialists and reducing costs. This latter role has raised questions about the quality of care delivered by managed care organizations which may limit referrals to specialists deemed necessary by primary care doctors as well as their patients.
Limited resources, together with the application of expanding technology for dubious gains, are forcing consideration of the ethical as well as the health and economic consequences of medical care. Resistance is growing to the technological prolongation of life when the quality of life has deteriorated beyond the point where it is worth saving. The state of Oregon, in the United States, has even introduced the concept of limiting funding for very expensive procedures to patients who fit certain criteria deemed to make the procedure cost-effective.
The principal aims of public health in the immediate future must be to find an appropriate balance between the provision of (a) sophisticated, technology-dependent health care at an affordable cost; (b) curative, complaint-driven medicine; and (c) preventive/health promotion services. The ideal balance will be partly determined by the resources that the country can devote to medical care. In developing countries greater emphasis should be placed on cost-effective preventive/health-promotion services than on expensive curative complaint-driven care.
As noted above, the circumstances of life and the way people live largely determine their health. Thus a prime responsibility for public health is to develop effective strategies to promote healthful conditions and lifestyles. One approach is to assure that local, national, and even international milieux favour healthful behaviour, as in the various national and WHO campaigns against cigarette smoking and the worldwide struggle to promote breast feeding of infants. Such activities, however, often result in confrontation with powerful entrenched economic interests. Tactics in the struggle to turn public policies explicitly towards the side of health, therefore, must be high on the public health agenda.
Another approach is the so-called medical model: that is, using the doctor–patient relationship, or analogues of it, through a one-to-one or sometimes a small-group effort in a health-oriented environment to guide individuals towards healthful behaviour. It offers promise particularly when people have, or can be induced to have, concern about particular health problems such as cancer or heart disease, and then are willing to undertake the indicated habit changes. Doctors often have been reluctant to devote the effort needed, partly because of their discouragement with the results. Positive change, however, can be achieved with adequate protocols (Manley et al. 1991).
A third approach is to use the community intervention model for promoting more healthful behaviour. Particularly in developing countries people tend to consider themselves primarily as a member of a family and a community. Changing established community norms can, therefore, often influence people to adopt healthier behaviours. Community intervention can be initiated by identifying the leaders or trend setters in a community and enlisting their assistance in influencing the members of their community.