Our conceptions of the determinants of health change periodically. At certain times socioeconomic factors have figured predominantly in policy-making; at other times the emphasis has been largely on identifying the causes of disease and treating the sick. Theories about the determinants of health?indeed, the definition of health?necessarily affect how illness is defined, what public policies are initiated, and how resources are allocated.

The National Health Services was introduced in the United Kingdom in 1948. At that time, it was believed that the gradient in health across the social classes (the highest social class had the lowest mortality rates, and the lowest social classes had the highest mortality rates) would be decreased if the financial barriers to health care were removed.1 Similar arguments were used when Canada introduced its national insurance program for health-care services nearly two decades later. In the 1970s the Merrison Royal Commission on the National Health Service in the United Kingdom 2 was surprised to find that the gradient in mortality across social classes had actually widened even though mortality rates had continued to fall. In 1977, the Labour government established a research group, headed by Douglas Black, the Chief Scientist in the Department of Health and Social Security, to look more broadly at the factors influencing health. A major conclusion of this compelling report, often referred to as the "Black Report,"3 was that while health care contributed to improved health and well-being there were socioeconomic factors of equal or greater importance in determining health and well-being. These factors were primarily causing the gradient in health across social classes.

The publication of the "Black Report" unleashed a vigorous and, at times, acrimonious debate and a deluge of studies. Black's working group was itself split over how resources should be allocated to reduce the inequalities in health. As Sir Douglas Black explained:

We were all agreed that education and preventive measures, specifically directed towards the socially deprived, were necessary. But the sociological members of the group (Townsend and Smith) considered that the consequent expenditure should be obtained by diversion from the acute services. On the other hand the medical members? and that means both of us (Black and Morris)?felt that the acute services played a vital part in the prevention of chronic disability and could not be further cut back without serious effects on emergency care, on the training of doctors for both hospital work and for family practice and on the length of waiting lists. We spent a long time, without real success, trying to resolve this matter. 4

The relative importance of investments in health care versus investments in other determinants of health is still an unresolved issue. The "Black Report," recent population-based epidemiological studies, and new insights from medical science have begun to give us a better understanding of how socioeconomic factors influence the health and well-being of populations. 5 Some quite striking perspectives have emerged from recent studies of the records in Western countries over the last three hundred years. The early period of our history provides some insights about our changing social environments and health.

PRE-INDUSTRIAL REVOLUTION

Ester Boserup has provided an informative account of hunter-gatherer societies and the Agricultural Revolution. 6 The hunter-gatherer societies had limited supplies of food and were constantly moving. Since only a small number of young children could be coped with under such conditions, birth spacing, infanticide, and short life expectancy constrained population growth. These groups, in addition to being affected by changes in food sources, were also exposed to physical hazards, predators, and, presumably, in certain environments, to pathogens.

The basic social structure of the hunter-gatherer societies was the troop or tribe (usually fewer than one hundred individuals). Because the groups were so small, there was a great deal of social interaction and support. Since social support appears to influence health and well-being, 7 the individuals in these simple social units may not have suffered from the negative effects on health of social deprivation that are found in societies today.

A different social framework emerged in the agricultural evolutionary stage, about ten thousand years ago, and began what some have called our experiment with civilization. Populations became less nomadic. New social environments with hierarchies were created through the establishment of farming communities and towns. Mechanisms for the control of land, food production, irrigation systems, and organization of labor evolved to ensure that these more complex systems could work. These new social orders did not have the collective, communal aspects of the hunter- gatherer societies. As Boserup points out, many hunter-gatherer societies stayed away from the new order to protect their communal form of existence. It has been suggested that hunter- gatherer societies knew of the technologies necessary for agriculture long before the development of agriculture.

In the towns and cities that emerged, the quality of the water supply and sanitation systems became factors influencing health. The increased population density created extreme vulnerability to any new infectious agent that swept into the population. In addition, wars were largely fought over controlling the sources of food and its distribution. In this period, as today, war often contributed to famine and epidemics. Although medicine emerged as a profession during this period, the causes of disease were poorly understood and therapies were limited in their effectiveness. Despite these factors, there was steady population growth: from approximately 10 million in 8000 B.C. to approximately 750 million in A.D. 1750.

Towards the end of this period insight into socioeconomic policies and the health of populations was gained. In the sixteenth century the authorities in England recognized that famines were man-made rather than natural disasters. Food was available, but
the lower classes could not gain access to it. 8 The state interfered and surplus food was supplied to the poor. This intervention angered farmers, producers, and merchants and contributed to the grievance against Charles I and the Civil War. After the revolution the new government abandoned the Tudor-Stuart program of food relief. This policy change subjected England to nearly two centuries of periodic famines. For the poorer members of the population, food riots became common. The issue was not food production, but destruction. After the Industrial Revolution, the government reinstated the old Tudor-Stuart program.

One of the criticisms that has been raised about the role of better nutrition in the improved health of populations is the observation that prior to the Industrial Revolution the peerage in England had the same mortality rate as the general population even though they had access to abundant supplies of food. 9 One explanation is that an abundance of food did not ensure that the upper-class children had a better diet than the general population. 10 After the Industrial Revolution, and its associated cultural and social changes, the life expectancy and height (a measure of the adequacy of nutrition during childhood) of the peers increased rapidly, while those of the general population lagged behind. Interestingly, a health gradient between the peers and the rest of the population emerged only after the Industrial Revolution.

THE INDUSTRIAL REVOLUTION

Although there were many technological innovations that affected socioeconomic development following the Agricultural Revolution, a major change occurred when it became possible to harness fossil fuels as a source of energy. Prior to this, slaves or serfs were used for most physical labor. Unfortunately, there is little data detailing the differences m the health and well-being of serfs and slaves versus those who were more privileged before the Industrial Revolution. As Rosenberg and Birdzell have emphasized, the Industrial Revolution was associated with vastly enhanced prosperity for Western societies, which led to better health, the disappearance of slavery and serfdom, and the development of democracy and universal suffrage. 11 During this period we find a substantial improvement in health and a dramatic rise in population. The world population has increased from approximately 750 million in 1750 to nearly 6 billion today. The decline in mortality rates over the past 150 years is one of the great triumphs in human history. A UN report in 1953 attributed the trend to four factors: 1) public health measures; 2) advances in medical knowledge and therapeutics; 3) improved personal hygiene; and 4) improved standards of living. 12

McKeown and Brown, attempting to better understand why health improved, explored factors influencing the major decline in mortality rates in the United Kingdom after 1840.13 They found that the bulk of the change in mortality rates could not be explained through medical intervention because there were no effective treatments for the major causes of death during most of this period. Furthermore, a large decline in mortality from airborne diseases could not be easily explained by the improved water and sanitation systems at the end of the 1800s. McKeown's conclusion was that the decrease in mortality was due to improved prosperity and nutrition. 14

Critics pointed out that while McKeown's argument about improved nutrition was obviously part of the story, he gave too little credit to public health measures and medicine. He also did not account for discrepancies, such as why the mortality rate of infants and young children in the United Kingdom did not begin to fall until 1900 when the decline in death from tuberculosis started much earlier. 15 Reves showed that the increase in child spacing that occurred in the United Kingdom around the beginning of this century was sufficient to increase the median age of exposure, and thus decrease susceptibility, to infectious diseases. 16 In earlier societies, child spacing was, in part, driven by culture, population density, access to resources, and survival of the society. The dynamics of the practice of child spacing cannot be determined by a simple formula. However, increased birth spacing has been shown to have a positive effect on a nation's health.

Improved water systems and sanitation greatly decreased the number of deaths due to waterborne diseases. The greatest decline occurred during the latter part of the nineteenth century, when water and sanitation systems in Britain were improved. Also in the nineteenth century, the hygiene movement and its public health accomplishments 17 reversed the deterioration of the British environment that was associated with the growth of urban centers during the Industrial Revolution. The socially conscious citizens of an increasingly prosperous society drove their economic and political institutions to improve the urban environment, thereby improving health and well-being for the society.

Following McKeown's pioneering work, Fogel 18 and others 19 have provided new evidence about the relation between improved nutrition and changes in mortality rates during the Industrial Revolution. They shifted attention from famine (only a small factor in pre-industrial mortality rates) to chronically poor or inadequate nutrition as a determinant of health. Before the middle of the nineteenth century, national food production in countries like England and France was not sufficient to provide adequate nourishment to the lower class. The bottom 20 percent of the labor force took in enough calories to stay alive but not enough to do much work. 20 In addition, undernourishment led to weakened immune systems and increased vulnerability to infectious diseases. 21

Height and weight measurements have long been used as a means of better understanding the relationship between nutritional status and mortality. An individual's height in adulthood reflects the effects of the nutritional experience during the growing years, including the fetal period. Height at maturity is inversely associated with risk of chronic diseases and dying in the later stages of adult life. 22 Weight represents the balance between nutrition in adult life and energy demands. The association of height with adult mortality rates reveals not the effect of adult nutrition but of nutritional levels (and disease history) from conception to maturity. Individuals who are poorly nourished or overnourished in adult life show higher mortality rates than individuals who maintain an ideal weight for height. However, short men who maintain an ideal weight are at a greater risk of death than are taller men. 23 Height is determined by genetic factors and nutrition, and the relative importance of each in explaining individual variation in height is still being debated. However, population mean height over time, which is used in these population studies, is primarily determined by environmental factors. 24

In Western countries, where records are available, the improvement in nutritional status during infancy and childhood, as estimated by changes in the mean height of the populations, is associated with a decline in mortality rates. Examination of English and American data has shown that Americans achieved mean heights and levels of life expectancy by the middle of the eighteenth century which were not achieved by the British upper classes until the beginning of the twentieth century. 25 The evidence from these studies also shows that the lower classes in England did not show a marked increase in height until this century. Countries in which access to nutritious food varies by social class, for whatever reasons, tend to show class gradients in height and health status. In countries that have a high degree of income equity and equitable access to good food, height differentials by socioeconomic class have largely disappeared. 26

The historical records since the Industrial Revolution show fluctuations in mean heights in populations in Western countries that appear to be related to socioeconomic factors such as the state of the economy, income distribution, and the effects of urbanization. These studies of the relationship between poor nutrition during early life and health and well-being in later life have shown that chronic health problems are more common among short or stunted men than among tall men. 27 Rejection rates for recruits into the Union army in the US Civil War, based on medical conditions, were, coincidentally, inversely correlated with the height of the potential recruits.

Fogel 28 notes that individuals in the last century who survived into the later stage of adult life were not freer of chronic disease than are persons of the same age today. He makes the point that reliance on cause-of-death information has led to a significant misrepresentation of the distribution of health conditions and an unfortunate separation of the epidemiology of chronic diseases from contagious diseases. Poor development during early life, as a result of poor nutrition, not only increases the risk of dying from contagious diseases, it also increases the likelihood of chronic disorders in adult life. The evidence also indicates that this phenomenon is not disease-specific, but is related to the development of the immune system and other organ systems. 29

A historical analysis of the influences of economic growth and improved prosperity on health and well-being is constrained by the limited information available. Thus, while the case for improved nutrition, particularly during childhood, seems clear, the role of other factors, such as better nurturing of children, the environments in which individuals live and work, and other socioeconomic factors, cannot be readily determined. More recent studies have begun to show the roles of these other factors.

COMPETENCE, COPING SKILLS, AND HEALTH AND WELL-BEING

The strong and pervasive relationship between an individual's place in the social structure of society and his health status is striking. Kitagawa and Hauser showed compelling evidence of different rates of mortality according to socioeconomic class in the United States between 1930 and 1960. 30 For several major causes of death, the rates were highest for the lower social classes. Even though the mortality rates in the United States have continued to decline, the social gradient in health, as measured by levels of income and education, is still present and the differences in mortality rates have widened. 31 This suggests that the widening in mortality rates is related to changing socioeconomic circumstances, such as increasing inequalities in income, education, and housing, a falling standard of living for a large segment of the US population, and limited access to health care for the poor and least educated.

Although life expectancy has improved for all social classes in the United Kingdom for the last sixty years, the gradient in social class mortality has been widening. 32 In contrast, in Scandinavian countries the gradient in health has not widened and life expectancy has increased for all social classes. 33 It has recently been reported that the mortality rate for the lowest social class in Sweden is less than that for the top social class in the United Kingdom. 34

One of the best studies of the relation between socioeconomic factors and the health of the middle class is the Whitehall civil service study. This longitudinal study provides direct measures of the health of individuals against their position in a well defined job hierarchy. 35 A striking finding from this study is the clear social gradient in health. As in larger population studies, 36 among those lower in the hierarchy there was found to be a higher risk of death from coronary heart disease, strokes, cancer, gastrointestinal disease, accidents, and suicides. The Whitehall study reported that the risk of dying of a heart attack for those in the bottom tier was more than 2.5 times that of the top tier. Marmot has shown that adjusting for conventional risk factors, such as cholesterol, blood pressure, and smoking, accounts for about 25 percent of the civil service social gradient in coronary heart disease. The remainder of the risk is related to factors in the social environments in which those in the civil service live and work. What in the social environment influences our vulnerability to a wide range of diseases and has an effect equal to or greater than more conventional risk factors? Since the civil service is largely a middle-class population, the "something" that influences health is not affecting some underprivileged minority, but is affecting a larger population.

There are many beneficial medical interventions available today for sick or injured individuals. There are also a number of interventions of questionable benefit. In the Whitehall study, it was concluded that differences in medical care could not account for the three-fold differences in mortality among civil servants. 37 The Whitehall study also shows that life-style (e.g., smoking) is strongly influenced by an individual's position in the social hierarchy. The study also reinforced a key conclusion from the historical analysis: the mean height of the civil servants, in each job classification, correlates with position in the job hierarchy, sickness-absence rate, and risk of dying. 38

An individual's sense of achievement, self-esteem, and control over his or her work and life appears to affect health and well-being. Studies in Sweden have shown that individuals in high demand jobs who see themselves as having little control over their work have a much higher incidence of coronary heart disease than do people in similar jobs who believe they have control. 39 Similarly, the Whitehall study found that a high proportion of people in the lower tiers of the civil service feel they have less control of their work than do individuals in the top tiers of the civil service. 40

How competence and coping skills relate to vulnerability to disease may be explained by improved understanding of the links between the brain and the endocrine pathways and the immune system. 41 We now understand some of the biological pathways through which individuals, coping with the demands of the environment in which they live and work, can influence the host defense system and disease expression. One set of animal experiments found that a friendly, supportive environment influences the process of diet-induced atherosclerosis. In these studies, two groups of rabbits were fed a cholesterol-rich diet. Those that were treated kindly (i.e., had music played to them) had 60 percent fewer incidences of atherosclerosis than those given the usual laboratory treatment. 42 Another research group working with monkeys found that an unstable social environment can accelerate coronary artery atherosclerosis, and that animals in the same colony, fed the same high cholesterol diets, show very different degrees of coronary artery occlusion depending upon their position in the hierarchy of the group. 43

Emerging evidence from fields such as psychology and the neurosciences points to how nurturing or stimulation influence brain development, particularly when it is most plastic. 44 The modifications and connections that are formed among the billions of cells in the cerebral cortex occur very rapidly during the first few months of life and continue throughout childhood. The development of the brain is strongly influenced by the quality of the nourishment and nurturance given to infants and children. The stimuli affect not only the number of brain cells in the cortex and the number of connections among them, but also the way the nerve cells are "wired." The stages in the development of the brain appear to be linked so that events early in life affect the development and function of the brain at later stages. In addition, in adverse environments activated stress hormones can have a negative effect on brain development and can damage neurons, leading to permanent defects in memory and learning. 45 Studies have suggested that children who were better nurtured in early life are healthier and do better in adult life. 46 There is evidence from studies in animals ranging from rats to nonhuman primates that show that this relationship exists. 47

This new understanding of the mind-body influence on disease expression also has relevance to some of the earlier observations. Could the post-1900 improvement in infant mortality in Britain 48 have been due, in part, to the link between breast-feeding and immune system responses, including the mother's early response to antigens in the infant's saliva? A mother, who is in circumstances that she has difficulty coping with and whose mind- body dynamics are suppressing her immune capability, may not be adequately building the defenses of the child she is feeding.

McKeown observed the steady decline throughout the nineteenth and twentieth centuries in mortality from tuberculosis, a disease which affects primarily children and young adults. 49 We know that tuberculosis is influenced not only by family age, structure, and crowding but also by host response capability, which may well be affected by the social environment as well as adequacy of nutrition. Thus, it may be that the increased prosperity and control people had over their lives after the Industrial Revolution, accompanied by improved nutrition, increased the population's host defense capabilities and this inhibited expression of the disease. The relationship among the nervous system, the endocrine system, and the immune system is emerging as a pathway that can help our understanding of the changes in health which are associated with changing social and economic conditions.

People's positions in the hierarchy of a society, the degree of control they enjoy, and the adequacy of their diet appear to be important factors in determining vulnerability to a wide range of diseases. The relationship between the quality of nurturing and adequacy of nutrition in early childhood and health risks in adult life has implications not only for health policies but for policies concerning the competence and coping skills of the population (human capital). This is a key factor in determining economic growth. We need to better understand how economic forces influence the quality of social environments and human development. Countries with major improvements in health status and less inequality in health tend to be countries that are prosperous and have a high degree of social and income equity, and a small proportion of children living in poor social environments. Are societies that are more coherent or communitarian in character likely to provide better environments for health than are extremely individualistic, fragmented societies? How does economic growth and prosperity determine the quality of social environments?

ECONOMIC GROWTH, PROSPERITY, AND HEALTH AND WELL-BEING

 In a recent essay on economic growth, The Economist said: "true enough, economists are interested in economic growth. The trouble is that, even by their standards, they have been terribly ignorant about it. The depth of that ignorance has long been their best kept secret." 50 A key issue has been the inability of the theoretical framework of neoclassical economics to cope with the role of technological innovation as an endogenous force in economic growth. The new framework of understanding of the determinants of economic growth, that embraces the role of technological innovation, 51 makes it important to understand better the relationships between technological innovation, economic growth, and the effects of these changes on society.

In his analysis of the improvements in the health of populations since the Industrial Revolution, Fogel points out that technological innovation can be a mixed blessing for populations that have to live through the associated socioeconomic changes. 52 For example, there have been periods of technological change and vigorous economic growth which produced limited, if any, improvements in the health status of the populations. 53 As Sen has pointed out, how societies create and distribute their wealth determines the health and well-being of the population. 54 In periods of profound technological change, with associated changes in wealth creation and distribution, individuals, particularly the young, will be at risk.

Changes since World War II in Eastern Europe and Japan illustrate this relationship. The decline in the economies of Eastern Europe has been associated with a decline in the health status of the populations while the improved prosperity of Japan has been associated with a marked improvement in health status. In a recent analysis for the World Bank on the decline in health status in Eastern Europe, Hertzman concluded that, in addition to the deterioration in the physical environment, a strong factor seems to be the deterioration in the quality of the social environment in which families live and work. 55 In contrast, the extraordinary improvement in the health of the Japanese 56 is associated with enhanced prosperity and what appears to have been a remarkable ability to sustain the quality of social environments and reasonable income equity throughout the society.

Wilkinson has found in his analysis of a number of Western countries that life expectancy is correlated with the degree of income equity in the society. 57 A recent study of Northern England showed a widening inequality in health that was linked to increasing income inequality. 58 How societies create and distribute the resources necessary to sustain their populations is a fundamental question. Adam Smith concluded that there were sectors of the economy that produced the wealth that made other activities in society possible. Smith described these sectors in his chapter entitled "Of the Accumulation of Capital, or of Productive and Un-Productive Labour:"

The labour of some of the most respectable orders in the society is, like that of menial servants, unproductive of any value, and does not fix or realise itself in any permanent subject, or vendible commodity which endures after that labour is past, and for which an equal quantity of labour could afterwards be procured. The sovereign, for example, with all the officers both of justice and war who serve under him, the whole army and navy, are unproductive labourers. They are the servants of the public, and are maintained by a part of the annual produce of the industry of other people. Their service, how honourable, how useful, or how necessary soever, produces nothing for which an equal quantity of service can afterwards be procured. The protection, security and defence of the commonwealth, the effect of their labour this year will not purchase its protection, security, and defence for the year to come. In the same class must be ranked, some both of the gravest and most important, and some of the most frivolous professions: churchmen, lawyers, physicians, men of letters of all kinds, players, buffoons, musicians, opera-singers, opera- dancers etc. 59

The new understanding of the factors determining economic growth has implications for Smith's splitting of the economy into productive and nonproductive labor. Since both sectors are important to a society, the productive labor section can be considered the primary wealth-creating sector (the engine of economic growth) and the other sector, the secondary wealth- creating component (the quality of the environment in which we live and work). When the primary wealth-creating sector falters, the income that flows to the secondary sector decreases, with associated changes in our social environment that can reduce our quality of life. The old economic theory tended to treat all outputs in the economy as being equal in wealth creation. The new concept clearly brings out the importance of a better understanding of a healthy primary wealth-creating sector and the synergy between this sector and the secondary wealth-creating sector. Many activities in the secondary sector, like some aspects of education, health care, and the support of children, are key parts of the infrastructure for all innovative economies.

Britain is regarded by many as a nation that has failed to make investments during this century in new technologies on the scale necessary to maintain its wealth creating capacity, and its economy has fallen behind those of other developed countries. 60 An interesting question is how many of the inequalities in health in the United Kingdom, particularly in the regions of major economic decline ,61 are products of the failure to invest in the key technological innovations that determine economic growth?

Krugman makes the point that the United States has two major problems: slow growth in productivity and rising poverty. 62 To increase the nation's wealth through enhanced productivity, ideas, and innovation is key. To help control expenditures, he points out, it is necessary to make the nation's health-care system more cost effective. In a sense, we are back to the debate in the "Black Report" concerning the need to allocate resources wisely in the secondary wealth-creating sector of our economies. In Canada this debate has become part of the policy considerations concerned with health in the provincial governments. 63 In Manitoba, the new Centre for Health Policy and Evaluation has shown from its analysis of the records of their health-care system 64 (a proxy for the health status of the population) that there is a clear gradient in health against measures of social deprivation. It is not lack of access to health care that is setting this gradient but the underlying social economic factors (unemployment, income, and education) as in Marmot's study of the Whitehall civil service. As might be expected, the most deprived part of the population places the greatest demands on the health-care system. Manitoba is trying to confront the need for reallocation of resources, from the least appropriate health-care expenditures to the social needs of the population in greatest difficulty, particularly children in poverty. As Sen has pointed out, it is not the level of wealth a country has that improves the health of the population, but its commitment to allocate resources to key sectors, such as mothers and children, education, and adequate nutrition.65 Canada, for the past twenty years, has not been creating sufficient wealth to sustain its consumption in the public and private sectors. Consequently, it has borrowed to maintain its standard of living, leading to the largest external debt per capita (private and public sector) in the developed world.66 Canada faces the challenge of trying to sustain its social systems, including health care, social support, and education with diminished resources while simultaneously trying to rebuild the economy.

To sustain quality social environments with diminished resources is a difficult task. It is possible that societies with high-quality social capital will be better able to adjust than will fragmented individualistic societies. Societies that have a strong, coherent sense of what is important, and a collective will, will probably be most successful. Putnam's description of what constitutes "civic societies" appears to be important in this regard.67

It is time to integrate our understanding of the determinants of health and the determinants of economic growth. Governments and their societies are mistaken to concentrate on the economics of business cycles rather than the long-term forces affecting economic growth, prosperity, and health and well-being. Fogel has concluded that 50 percent of the economic growth in Britain since the Industrial Revolution has been due to better nutrition of the population.68 A society that handicaps large segments of its population during periods of major technological change may be handicapping its future economic growth. We now have a better understanding of the relationships among economic growth, prosperity, and health and well-being, and the need for a long- term, integrated perspective on the determinants of health and economic growth. Can we make intelligent and wise use of this understanding?

 John W. Frank is Director of Research at the Institute for Work and Health, Toronto, and a Fellow of The Canadian Institute for Advanced Research's Population Health Program at the University of Toronto.

 J. Fraser Mustard is President of The Canadian Institute for Advanced Research Toronto, Canada

Notes for "Determinants of Health"