Multiple Determinants of Health

In this chapter we’ll be looking at the determinants of health, especially the social, ecological and political determinants. Of course biology is absolutely critical too, but that is most often dealt by clinical medicine. But we will also look at the interplay of these other determinants with human biology and ultimately how they shape health at the level of populations.

Let me start with the story of Rudolf Virchow, who was an eminent pathologist in 19th Century Germany. He was also the founder of the Anthropological Society of Germany. And he had a place in the Kaiser’s court. A highly respected academic. When he was sent off by Kaiser, or the emperor of Germany to investigate an outbreak of typhus in Silesia in Prussia. He came back with a report not looking at the biology of the disease, but on the social circumstances which caused the outbreak. He said the principle cause of that outbreak of typhus in Upper Silesia was poverty and inequity. And he recommended that there should be measures taken to reduce poverty including abolition of feudal privileges and greater levels of democracy. That did not make him popular in the court, but as a philosopher of social medicine Rudolf Virchow has a very prominent place. He said, do we not always find that diseases of the populace traceable to defects in society? If disease is an expression of individual life under unfavorable circumstances, then epidemics must be indicative of mass disturbances.

He went on to say that these mass disturbances are disturbances of culture and therefore great social changes sometimes also bring epidemics in their wake. What was true of typhus in the 19th Century is true of tobacco in the 20th Century and now we are seeing other social movements which are also resulting in the epidemic of overweight and obesity because of unhealthy foods. Even in Victorian London, poor living conditions were recognized to be responsible for ill health. The Black Death of 1655 was again, strongly related to poverty and poor living conditions. And when we had epidemics in London or the United Kingdom, then the rich left the town for their estates while the poor who were to remain, suffered. And we have seen the descriptions of this kind poverty and deprivation affecting health in the books of Charles Dickens. When we look at how sometimes social circumstances can actually change for the better and thereby bring about improvements in public health, we also see the decline of tuberculosis antedated the discovery of drugs against the tubercular bacterium, or the bacillus tuberculosis. And that is where McKeown brought about his famous thesis that it is the social conditions which actually are responsible for decline in infectious diseases in countries which are improving economically.

While it is true that science and technology are also very important allies in bringing about public health improvements, we definitely have to acknowledge the important role of socioeconomic development. But this development also has to be equitable. Now we recognize that if you actually look at populations and compare them. We also find out that some of the diseases which appear to be very common in some countries are far less common in other countries, even at the same level of economic development. For example, in Finland, in the 1960s and ’70s, coronary heart disease was extremely common. Whereas at the same time in Japan, coronary heart disease was very rare. And we find that the way the populations live in terms of their living habits, of diet, physical activity, all of them are responsible considerably for these inter-population differences.

Geoffrey Rose from the United Kingdom, a famous epidemiologist, while studying cardiovascular diseases across different countries said, sick individuals come from sick populations.

If your average cholesterol level in the population is high, the number of people who will get heart attacks because of high cholesterol is going to be high. Similarly if your average blood pressure in the population is high, the number of people with hypertension who are going to get a stroke is high. So we have to really alter the population dynamics of risk acquisition and risk reduction if you want to make an impact in public health across the population. Now we also know that migration into urban environments also accounts for a great deal of this change. When you look at Kenyan nomads who live in very rural conditions and London civil servants at the same time, this is one of the earlier studies of Geoffrey Rose, you find a marked change in the distribution of the systolic blood pressure across these two populations. In London, the entire distribution is far to the right. That means even the average blood pressure as well as the proportion of those with hypertension is far higher than those in the Kenyan nomads. And therefore the way in which we lead our lives makes a difference.

This doesn’t mean that everybody has to live in relatively primitive conditions and shun modernity, but we are to make sure that as we advance towards modernity we retain some of our healthy living habits. And that is the basis of public health. So when we look at the principles of risk and prevention we understand that since much of this is determined by the population profile of a risk factor, small reductions in risk factor levels when achieved across the whole population. That means when the whole population distribution shifts to the left, shifts to a better level, then that results in a large reduction of adverse events like strokes and heart attacks across the population. Even though the individual shifts are small, cumulatively the population benefits are large. At the same time you have to also look at people who are at the high risk end of the distribution and who at the individual level have a very high risk and we have to focus public health interventions to get them the appropriate mode of risk reduction therapies. So we need to combine both of these strategies.

These are not mutually exclusive but are synergistically complimentary. But when we look at what makes people healthy, or unhealthy, we realize that there are elements in the health system which are very important. The health workforce, are there enough doctors, nurses, allied health professionals? The infrastructure, are there well equipped health facilities? Do they have enough drugs, vaccines and technologies available and affordable across the population? How is health being financed? And what are the health information systems like? Do we get ready information on what the risk factor levels in the population are? Or what is the spread of disease across the population? How is the whole system being governed? Is it efficient? Is it suffering from corruption? Is it accountable to people? All of these matter in the health system. But over and beyond that, we also have to look at the social determinants of health and nutrition. For example, these are factors operating at the societal level. Like the availability of clean water, sanitation, food systems and agricultural systems which provide healthy nutrition across the life course to every individual. A clean environment, having as little air pollution as possible. Social stability, free from conflict and violence and having adequate degree of community participation.

Then all of these matter very much in terms of the societal forces. The level of development and distribution of incomes within society matters. At the personal level, income, education, occupation, social status, gender, participation in social networks, all of these are important social determinants of health. So when we really look at all of these, public health operates at each of these levels. But underlying all of these are political and economic systems which ultimately make choices with respect to many of these determinants. We recognize for example that as per capita income grows across countries, up to a certain level the life expectancy also increases.

Once you reach a certain level of about close to ,or beyond $3000 or $4000 per capita, then the effect starts plateauing off. And this is known as the Millennium Preston Curve. But the fact is, per capita income which means the overall income as assessed as the income per population, per unit, actually matters a lot in terms of life expectancy.

However, how this is distributed within the population also matters a lot. Like for example, in the United Kingdom, there’s a huge difference in life expectancy between one county of the United Kingdom and the other county of the United Kingdom. Almost, whereas one county has a life expectancy of 54 years, the other county has a life expectancy of 82 years. Again, even within the U.S. you have differences in life expectancy which is considerable between different counties. Where in Washington you have a predominantly black population, you have 63 years as their life expectancy. On the other hand, in Montgomery County, which has a predominantly white population, you have a life expectancy of 80 years.

Now we also know that because of income differences, but also because of educational differences and employment differences you can have substantial differences in mortality rates. For example, if you look at the mortality rates across different classes of occupation, the people who are in higher grades of employment in the Whitehall which is the secretariat in the United Kingdom, they have had much lower levels of mortality as compared to some of those in the lower professional grades who, where the stress levels are much higher. And in terms of health inequalities we also recognize that educational levels play a great role.

Even at the same levels of income, differences in education make a lot of difference. Those who have had university education have a much lower mortality as compared to those with only elementary education. So there is a growing recognition that whether, between countries or within countries, we ought to be addressing inequality much more effectively. Michael Marmot who headed the WHO Commission on Social Determinants of Health remarked that the fact that there is a spread of life expectancy of 48 years among countries and a spread of 20 years or more within countries is not inevitable. This is not something that is a given, irreversible. We can, by addressing through appropriate public health strategies and equitable socioeconomic development and distribution bring about a shrinkage of these huge gaps that lie within life expectancy across and within populations. And we see this can happen in different countries where the differences between the wealth quintiles can be substantial even in terms of the number of births that are attended by skilled birth attendants. And within countries we find that the poorest, again, have unattended births with a likelihood of higher maternal mortality. But as universal health coverage takes place across countries, even in countries with lower incomes, we find that these differences across wealth quintiles are substantially reduced or even obliterated. So we ought to be really looking at universal health coverage to reduce health inequalities brought about by income inequalities. We also recognize that by making determined efforts to bring about greater equality in society you can overcome many of the existing inequalities. Brazil is a remarkable success story in this direction. After the revolution in Brazil where the military dictatorship was overthrown, and a constitution enshrining the right to health was adopted, Brazil had a number of social initiatives which were directed against reducing income inequality and reducing poverty. And that has had its effect on health. If you look at the stunting rates across income quintiles, then we find that earlier on we had a huge gap pre-revolution in the stunting rates between the high income groups and the low income groups. But subsequently we find that in the last decade these differences have greatly narrowed and we find the stunting rates in the lower and the high income groups are virtually very similar. So by bringing about a greater degree of equality in distribution and greater access to nutrition, also other social determinants of health as well as health services we can actually reduce some of the gaping health inequalities that are a major problem in terms of inequitable development. And that is a very important mandate for global health. How best can we reduce inequalities in health across populations and within populations? We do have the knowledge, we just have to apply it political will and determination supplemented by professional skill brought about by good public health systems.