Overview and framework
The public health context
Models of the determinants of health
Global and local determinants of health
The determinants of health and disease
Lifestyles and other behavioural determinants
This chapter begins by providing an overview of the context for public health practice at the beginning of the twenty-first century with an emphasis on the current phase of economic globalization. The next section summarizes models of the determinants of health and disease relevant to public health research and practice, and provides a conceptual framework of these determinants incorporating both global and local perspectives. Finally, the major categories of the determinants of health status are briefly reviewed; the other chapters in this section explore these determinants in detail.
The public health context
A major transition in the health of human populations is occurring. Firstly, there have been broad gains in life expectancy over the past half-century and fertility rates are declining. Secondly, the profile of major causes of death and disease is being transformed; the pattern of infectious diseases has become more labile with new and old epidemic diseases emerging, and the burden of non-communicable disease is increasing. Finally, health inequalities between rich and poor are increasing both within and among countries.
The prospects for the future health of populations depend to an increasing extent on the processes of globalization and the emergence of global environmental changes in response to the burden of economic activity (McMichael and Beaglehole 2000). In addition to the immediate causes of disease, there are profound influences on population health status from social, economic, political, and environmental processes at multiple levels. The improvements in the health profile of developed countries over the past two centuries have resulted from both broad-based changes in the social, economic, and physical environment, in human ecology, and, to a lesser extent, from deliberate public health and medical interventions. In developing countries, health gains have begun more recently in the wake of increased literacy, family spacing, improved nutrition and vector control, assisted by the application of public health knowledge about sanitation, vaccination, and the management of infectious diseases (Powles 1992).
Public health is ‘the art and science of preventing disease, promoting health, and prolonging life through the organised efforts of society’ (Committee of Inquiry 1998). There are two major themes underlying the modern public health task. Firstly, as social and material inequalities within a society generate health inequalities, an important public health task is to identify through research the underlying determinants of these health inequalities. That knowledge must then be applied, in part through professional practice, to the development of health supporting social policies. Secondly, longer-term changes in the structure and conditions of the social, economic, and natural environments, at both the local and the global levels, affect the level and sustainability of good health within populations. The scope of contemporary public health practice includes the health consequences of rapid urbanization, demographic change, the globalization of economic, social, and cultural relations, and human-induced global environmental changes. To be most effective, modern public health research and practice should be based on an up to date understanding of the broad determinants of the health and disease status of human populations.
Models of the determinants of health
Over the last 50 years there have been important shifts in the manner in which the determinants of health are viewed. Four distinct, but overlapping, perspectives on the determinants of health can be identified:
the biomedical view
the lifestyle approach
the broad socio-economic approach
the population health view.
The biomedical paradigm emerged towards the end of the nineteenth century based on bacteriological discoveries. This paradigm is still dominant. It is based on the strength of the molecular and genetic sciences and is characterized by adherence to ‘objective’ sciences and the search for causes of specific disease in individuals and their constituent parts. The huge investment in the human genome project typifies this view of human health and its determinants.
The Lalonde Report to the Canadian government in 1974 began the modern era of health promotion by proposing a broader view of health (Lalonde 1974). The report asserted that positive health was not attainable for the majority of the population through a concentration of public health funds on personal services. The report described the health field in terms of four fields: human biology, environment, lifestyle, and health-care organization. Unfortunately, the emphasis rapidly shifted to the role of individual lifestyles in determining health status.
The 1986 Ottawa Charter emphasized the role of factors outside the health-care sector and, in particular, the social and economic determinants of population health status (Ottawa Charter 1986). This view did not gain widespread acceptance outside of the public health and health promotion communities.
Since the early 1990s and in response to the fiscal crisis affecting health-care systems worldwide, the ‘population health model’ has received increasing support (Evans et al. 1994). This model has replaced the earlier ‘health promotion’ model as a guiding framework for health policy and practice. The central message of the population health model is that health in human societies, as opposed to individual health status, is powerfully influenced by the wealth-generating capacity of a nation and the manner in which this wealth is distributed. The central assertions of this model are as follows:
the major determinants of human health status are cultural, social, and economic factors at both the individual and population levels
these factors are independent of medical care input at the population level
societies that enjoy a high level and relatively equitable distribution of wealth enjoy a higher level of health status
at the individual level, health status is determined by the social and economic environment and the way in which this environment interacts with individual psychological resources and coping skills.
Contemporary evidence in support of the population health model and of the prime importance of wealth and prosperity comes from Japan, which has the world’s highest life expectancy at birth yet spends only a relatively small percentage of gross domestic product on the health system (Marmot and Davey Smith 1989). Another important strand of the model is the evidence from the Whitehall studies in the United Kingdom on the role of relative poverty in producing major health inequalities. The social determinants of these inequalities appear to be of more importance than the role of the major risk factors (smoking, elevated blood pressure and cholesterol levels, and physical inactivity) for non-communicable diseases (Marmot and Wilkinson 1999). The focus on social and economic determinants of health in the population health model is a welcome contrast to the mainstream biomedical model of health. However, the population health model has several limitations; in particular it downplays the importance of targeted public health interventions and the effects of improved living and working conditions in increasing life expectancy over the last 150 years (Szreter 1988). Clearly, wealth generation alone was insufficient to increase health status: public health and social reforms more generally were also involved. For example, the contemporary role of medical services in relieving suffering, enhancing quality of life generally, and improving life expectancy, particularly in poor countries, over the last 50 years is also underemphasized as described in Chapter 2.8. There is evidence that a medically based and high-risk approach to the primary prevention of non-communicable disease can be successful, even if it is not cost-effective (Hunick et al. 1997). Also, as far as the Japanese evidence is concerned, there appear to be large hidden costs in the private (home care) sector that is largely provided by women.
Another limitation of the population health model is that it underplays the importance of the current phase of economic globalization for public health practice (Hayes et al. 1994).
The links between wealth and health are obviously more complex than represented in the model. In fact, a high level of wealth at a national level is not a necessary prerequisite for high population health status. The final limitation is the lack of attention given to the importance of community involvement in health affairs.
Global and local determinants of health
The determinants of health are broad, extend from genetic influences to the social, cultural, and economic environment, and include manifold pathways by which these various factors operate to influence health and disease status at both the population and individual levels. The preferred model of the determinants of health is dynamic and interactive and adopts a life course approach to health status recognizing the complexity of the interplay between prenatal, early, and later life influences on the development and maintenance of health and disease states. This model is far removed from the more usual and more circumscribed ‘medical model’, which is based on a restricted biological view of disease aetiology and concentrates on the endstages of the disease production process.
The preferred model of the determinants of population health status places greater emphasis on both the role of the new global economy and its associated developments and on the role of people and communities. The new interconnected global economy has a major influence on and interacts with environmental, social, and cultural determinants of health (Fig. 1).
Fig. 1 The determinants of the health of populations.
Economic ‘globalization’ has been a long-evolving feature of a world dominated by Western society. For example, the onset of the twentieth century was a time of vigorous free trade, subsequently curtailed in the aftermath of the First World War. Contemporary globalization differs in both the scale and comprehensiveness of change, and in the associated decline in the nation-state’s capacity to set social policy. The West’s post-Second World War international ‘development project’ anticipated national convergence towards the model of Western democratic capitalism. Since the early 1980s, that project has evolved towards a globally deregulated free-market economy. These globalizing processes, in turn, have become a major determinant of national social and economic policies (Gray 1998). Thus, although responsibility for health care and the public health system remains with national governments, the fundamental social, economic, and environmental determinants of population health are becoming increasingly supranational. It is evident that this current global configuration of liberal economic structures and constrained social policies promotes social dislocation, economic inequalities, and political instability, each adversely affecting public health. Unless the moderating role of the state or of international agencies is strengthened, increasing competition for the world’s limited natural resources could become increasingly damaging to intercountry relations, local and global environments, and population health (UNEP 1999).
From a public health perspective, globalization is a mixed blessing (McMichael and Beaglehole 2000). On the one hand, accelerated economic growth and technological advances have undoubtedly enhanced health and life expectancy in most populations. At least in the short to medium term, material advances allied to social modernization and various health-care and public health programmes have yielded impressive gains in overall population health status.
On the other hand, aspects of globalization are jeopardizing population health through the erosion of social and environmental conditions, the global division of labour, the exacerbation of the rich–poor gap between and within countries, and the accelerating spread of consumerism. The primary health risks, reflecting the central impacts of globalization on social and natural environments, include the following.
Perpetuation and exacerbation of income differentials, both within and among countries, thereby creating and maintaining the basic, poverty-associated conditions for poor health.
The fragmentation and weakening of labour markets as internationally mobile capital acquires greater relative power. The resultant job insecurity, substandard wages, and lowest-common-denominator approach to occupational environmental conditions and safety can jeopardize the health of workers and their families.
The consequences of global environmental changes (includes changing atmospheric composition, land degradation, biodiversity depletion, spread of ‘invasive’ species, and dispersal of persistent organic pollutants).
Other more specific risks to population health status include the following.
The spread of smoking-caused diseases as the tobacco industry globalizes its markets.
The diseases of dietary excesses as food production and food processing becomes intensified and as urban consumer preferences are increasingly shaped by globally promoted and marketed images.
The diverse public health consequences of the proliferation of private car ownership, as car manufacturers extend their marketing.
The continuing and widespread rise of urban obesity, exacerbated by the above two developments.
Expansion of international drug trade, exploiting the inner-urban underclass and, more generally, the alienation of some young people in the context of ineffectual national control efforts and institutional weaknesses.
The infectious diseases that now spread more easily because of the distant and rapid connections around the world, the disruption of natural habitats, and the emergence of drug resistance.
The apparent increasing prevalence of depression and mental health disorders in ageing and socially fragmented urban populations.
A major manifestation of the increasing scale of the human enterprise is the advent of global environmental changes. While not directly caused by the globalization processes, global environmental change reflects the increasing numbers of humans and the intensity of modern consumer-driven economies (McMichael and Powles 1999). Humankind is now disrupting, at a global level, some of the biosphere’s life-support systems which provide environmental stabilization, replenishment, organic production, the cleansing of water and air, and the recycling of nutrient elements (Chapter 2.7). Earlier generations could take these environmental ‘services’ for granted in a less populated lower-impact world. Changes are now occurring in the gaseous composition of the lower and middle atmospheres. There is a net loss of productive soils on all continents, and depletion of most ocean fisheries and many of the great aquifers upon which irrigated agriculture depends. There is an unprecedented loss of whole species and many local populations. An estimated one-third of the world’s stocks of natural ecological resources has been lost since 1970. These changes to the earth’s basic life-supporting processes pose long-term risks to human population health.
The complementary global and people-centred approaches to understanding the determinants of health are key components of strategies for health improvement in the twenty-first century. The people-centred approach to public health has at its core the concept of empowerment, which means that the people of a community are in control of the public health process and are strengthened by it. The key to this approach is the adoption of a community development strategy where needs assessment and clear goals are central aspects (Raeburn and Rootman 1997).
There is a need for a balanced emphasis in both research and public health practice on the proximal, intermediate, and distal causes of health, disease, and disability. This balanced approach is in contrast to the more usual epidemiological approach that focuses on the proximal determinants, especially intrinsic biological and behavioural factors (McKinlay 1992).
The determinants of health and disease
Health is a social and cultural concept in addition to its fundamental biological characteristics. There are three basic sources of differences in the health of populations: hereditary determinants, socio-economic circumstances, and lifestyles and other behavioural factors. Gender differences span all three domains and cultural and political factors also play important parts in determining the health of populations.
The effects of genetic factors on the various components of health and the ageing process are not yet well known. It has been estimated that only 20 to 25 per cent of variability in the time of death is explained by genetic factors (Christensen and Vaupel 1996). About 50 per cent of variation in human lifespan is attributable to survival attributes that are fixed for individuals by the time they are aged 30, but only a third to a half of this effect is thought to be due to genetic factors. The influence of genetic factors on the development of chronic conditions, such as coronary heart disease and diabetes, varies considerably. However, from a practical point of view, the environmental determinants of these conditions still offer the greatest scope for prevention and control efforts.
Social and economic determinants of health refer to a wide range of factors that include occupational status, work conditions and security, educational attainment, housing environment and tenure, and family circumstances (Marmot and Wilkinson 1999) (see also Chapter 2.2). It is likely that each of these factors acts differently on health at each stage of life. Cumulatively these factors play a major part in determining the ‘social capital’ available to both individuals and communities.
An important question is the extent to which the roots of health inequalities lie in socio-economic circumstances earlier in life, compared with current circumstances. From life-history studies of childhood and adolescence it appears that social factors probably operate in a cumulative fashion (Kuh and Ben-Shlomo 1997). There are significant social class differences in height, growth, and other aspects of physical development, as well as in the incidence of infectious and other diseases and risk of injury. Vulnerability to physical ill health in childhood and later adult life is associated with poor parental socio-economic circumstances and low levels of parental education and concern (Wadsworth 1997). Cross-sectional studies also show differences in mortality and morbidity as a function of socio-economic status, across various disease categories throughout the life span. Educational attainment and marital status have also been shown in several longitudinal studies to be powerful predictors of mortality. In addition, age, gender, and socio-economic status influence disability-free life expectancy (Robine et al. 1992).
The economic consequences of unemployment and retirement place many citizens in positions of financial vulnerability. As populations age, in both the developing and the developed worlds, the issue becomes how to keep older persons economically active within their respective societies. No community is exempt from the financial hardships experienced by ageing and unemployed populations. As populations stop working, they lose not only the economic but also the social and psychological benefits of activity and purpose. Men seem to be particularly sensitive to loss of work and retirement.
Lifestyles and other behavioural determinants
Behaviours such as smoking, physical exercise, activity in everyday life, alcohol consumption, diet, self-care practices, social contacts, and work-style are important contributing factors to population health status and variations in ill health with age (Chapter 2.3). Changes in the population levels of several of these factors, for example smoking and inappropriate dietary habits, are probably responsible for an important fraction of the increase in life expectancy in middle-aged people that have occurred over the last three decades in many Western countries (Chapter 2.5 and Chapter 10.1). These gains are a result of the major declines in cardiovascular disease death rates that began in the mid-1960s in the United States and have since been experienced in many other industrialized countries, although not yet to the same extent in eastern European countries (Beaglehole 1999) (see also Chapter 9.3).
General health education messages have had only a modest impact on changing these health determinants in people from disadvantaged social circumstances. Attempts to change people’s health-related behaviour have been based on a superficial understanding of their social conditioning. The concept of prevention, like the concept of health, is a cultural and social construct. Interventions, therefore, have to be adjusted to different cultures and social circumstances and to the life experiences of different individuals, and have to take into account cohort and period effects and the powerful economic determinants of health, which are increasingly located at the transnational level. It will be increasingly important to locate prevention policies in the broad context of social and economic policy if current knowledge on the role of these health determinants is to be applied for the benefit of entire populations.
Gender differences in health status are apparent throughout the lifespan and one expression of this is the feminization of later age. Several reasons have been suggested for these gender differences (Chapter 11.2). Prominent among these are behavioural factors such as cigarette smoking, alcohol consumption, and exposure to occupational hazards. Conversely, women have a higher prevalence of chronic conditions and disabilities, particularly in old age. The influence of social structures on health for women goes beyond causes related to conventional socio-economic differentials. More attention needs to be given to the reasons for men’s shorter life expectancy and women’s greater burden of sickness and disability. The important role of ‘masculinity’ in shaping men’s expectations, behaviour, and thus health, requires further exploration and is likely to be as important as ‘feminine’ roles are in shaping the health of girls and women. Development of gender-specific health policies and health research is needed in all countries.
Different cultures assign different values to the parts people play at different ages within their societies. In certain cultures, older persons, for example, are assigned the tasks of government or other important duties and are regarded with great respect as community leaders. The particular impact of ageing on the health of indigenous older men is an under-researched area. It is known that most indigenous people, for example the New Zealand Maori, are severely disadvantaged from a health perspective. In industrialized cultures, older persons are often removed from the patterns of regular life when families are unable to fulfil caregiver roles, and are resettled in residential or skilled nursing institutions. Such environments can lead to diminished states of physical and psychological well being and mark the beginning of serious declines in health.
Political decisions shape the social and economic environments and the health systems that have important effects on the health of populations. Policies involving the organization and delivery of health services, national social security, and insurance programmes, for example, are major determinants of the health status of populations, and especially the young and old (Chapter 2.8). The collaboration of health advocacy groups in lobbying policy-makers and creating general awareness is a key element in promoting the health needs of specific communities. Non-governmental organizations provide health advocacy at the local, developmental level. Functioning in both developed and developing countries, these groups are vital members of the health improvement network, having direct access to populations and often also to the policy-making process.
This introductory chapter has illustrated the need for modern public health teaching, research, and practice to be grounded in both local and global perspectives on the determinants of health and disease in human populations. The challenges facing public health are great, and a comprehensive approach to health determinants will be necessary to achieve the full potential of all citizens of the world.
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