3 Analysing the causes of health problems and socially determined health

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Unit 5: Unravelling the causes of ill health


When you have completed this unit you should be able to:

5-1 What is health?

The World Health Organisation defines health as, “a complete state of physical, mental and social well-being, not just the absence of disease or infirmity”.

Health is a complete state of wellbeing not just the absence of disease.

5-2 What is disease?

A disease is a disorder of structure or function that presents with a set of recognised symptoms and signs.

The World Health Organisation defines disease as “a named entity that meets particular diagnostic criteria”. It is important to understand that somebody can feel unwell without having a recognised disease while others can have a disease and still feel well.

A disease is a named disorder of structure or function.

5-3 What do we mean by the determinants of health?

A determinant is a cause. Ill health does not occur randomly but has a cause or causes. By investigating who is ill and who is healthy, and which risk factors they are exposed to, we can start to unravel the reasons why some groups of people are less healthy than others. Understanding the determinants of health means that opportunities to prevent ill health can be identified. This process is called “epidemiology”. Epidemiology studies the distribution of disease and the relationship between risk factors and disease.

Epidemiology studies distribution of disease and the relationship between risk factors and disease.

5-4 How are the causes of disease established?

The causes of disease are usually established by studying:

Further investigations can then be done to see:

There are 2 distinct fields in public health that look at these questions:

This knowledge is useful when people want to do research or want to read original research to make their mind up about the results.

Epidemiology is a study of the relationship between risk factors and disease while biostatistics analyses and interprets data from research studies in public health.

5-5 Do public health and clinical practitioners think differently about the causes of ill health?

Yes. Public health practitioners and clinicians think differently about the causes of ill health because they use the information in different ways:

This simple understanding of cause and disease might help clinical management, but is less useful for planning prevention because people cannot be banned from smoking and malaria parasites cannot be eradicated. Instead, it is necessary to know more about why people smoke or why they become infected with a malaria parasite.

5-6 What is the epidemiological triangle and when can it be useful?

The epidemiological triangle is the traditional model for understanding the transmission of infectious diseases and how they are caused and possibly can be prevented. It recognises that there are important relationships between a disease causing agent (such as a microbe), its host (such as a person), and the environment in which they both live. The triangle looks like this:

Figure 5-1: The epidemiological triangle showing the relationships between causing agent, host and environment.

Figure 5-1: The epidemiological triangle showing the relationships between causing agent, host and environment.

The lines of the triangle represent the relationships between agent, host and environment. Prevention involves changing those relationships – or breaking the lines in the triangle.

If the disease-causing agent requires another organism to infect the host, another element called the “vector” has to be introduced into the triangle. In the case of malaria, this would be the Anopheles mosquito. An epidemiological triangle that contains a vector has more interactions that can be broken. An example of an epidemiological triangle for malaria is shown in Figure 5-2, together with examples of strategies for prevention.

Figure 5-2: The epidemiological triangle for malaria showing 3 interactions which could be broken.

Figure 5-2: The epidemiological triangle for malaria showing 3 interactions which could be broken.

Strategies for prevention of malaria include:

  1. Human-environment interactions: Identify sources of stagnant water, such as dumped tyres and uncovered household water sources such as drains or buckets.
  2. Human-Plasmodium interactions: In areas with a high malaria burden, mosquitoes are more likely to become infected with Plasmodium. Effective treatment and prevention of malaria in individuals has benefits for others as mosquitos are less likely to become infected. Humans can be protected using malaria prophylaxis.
  3. Human-mosquito interactions: Insecticide treated bed nets prevent mosquito bites.

An epidemiological triangle is used to understand the cause and prevention of infectious diseases.

If the agent must spend part of its lifecycle developing in the vector, the vector can also be called an “intermediate host”. The mosquito is an intermediate host for the malaria parasite. This terminology is often used when discussing worms and other parasites.

5-7 Is the epidemiological triangle useful for understanding non-infectious diseases?

The epidemiological triangle does not work well for non-infectious diseases because:

5-8 What is a “causal pie”?

A “causal pie” is one way of graphically showing causes when several factors are necessary to produce a disease. Each factor that contributes to the disease is shown as a slice of the pie. For the disease to develop all the slices in the causal pie must be present. Figure 5-3 shows 2 causal pies that represent the development of TB infection in 2 different people:

Figure 5-3: Causal pies for the development of tuberculosis

Figure 5-3: Causal pies for the development of tuberculosis.

You will note that exposure to TB occurs in both pies because TB infection cannot occur without it. On the other hand, not everybody exposed to the TB bacillus will develop the disease. Other component causes such as malnutrition need to be present for TB infection to occur.

Causal pies can be used to show that multiple factors are necessary to cause a disease. However they are limited to a few component causes, they do not show the relative importance of each component cause and they do not show how many factors interact with each other. Therefore they are too simple to explain most chronic non-infectious diseases.

A causal pie shows a number of factors needed to cause a disease.

Each slice of the pie is known as a “component cause” while the complete pie is called the “sufficient cause”. Any slice that is essential for disease is called a “necessary cause”.

Figure 5-4: Determinants of non-infectious disease including social and physical environment, life course events and access to healthcare.

Figure 5-4: Determinants of non-infectious disease including social and physical environment, life course events and access to healthcare.

5-9 What is the best way of understanding the underlying causes of chronic non-infectious disease?

In non-infectious diseases, a person (the host) may come into contact with a disease causing agent, but what happens is affected not only by the physical environment, but also by many personal factors including genetics, social influences that determine behaviour, by life events and access to healthcare. Therefore there are many layers of causes that interact with each other in a complex way to produce a chronic non-infectious disease.

Many factors interact with each other in a complex way to cause a chronic non-infectious disease.

5-10 Why is a model of interacting causes important in understanding chronic non-infectious diseases?

This sort of model is useful because:

The individual at the centre of this complex social and physical environment is in the best position to understand many of these factors and how they interact.

Finding the best way to analyse the relationships between risk factors in a complex system is an active area of research.

Case study 1

Rotavirus causes diarrhoea in infants and young children. It is shed in the faeces of an infected person and spreads to another person by mouth, in food, water and objects, and by hands.

1. Draw an epidemiological triangle with rotavirus (causing agent), young children (host) and environment on it. Think of ways to break each side of the epidemiological triangle and reduce rotavirus transmission.

See Figure 5-5 for an example.

Case study 2

A 50-year-old man with a family history of both heart disease and stroke is overweight and doesn’t exercise.

1. What factors in his environment could be altered to reduce his risk of these chronic non-infectious diseases?

Family and friends could support him in efforts to reduce his calorie intake. He could join a sports club or social group that encourages exercise and supports people who need to lose weight. These factors could affect his life style to reduce the risk of chronic non-infectious diseases, such as hypertension, diabetes, heart disease and stroke.

Figure 5-5: This is one example how to respond to the question.

Figure 5-5: This is one example how to respond to the question.

Unit 6: Socially determined health


By the end of this unit you should be able to:

6-1 What is meant by socially determined health?

Up until the 1980s, it was thought that poor people died of diseases of poverty and deprivation, such as infections and nutritional deficiencies, while richer people had “diseases of affluence” such as diabetes and heart disease. It is now clear that this is not true and that for most diseases, there is excess mortality in those who are less advantaged. The term “socially determined health” refers to the way in which health is determined by our sense of social well-being, and the effects on health of:

Therefore people who are socially disadvantaged tend to have poorer health.

Poverty, inequality, discrimination, marginalisation and social isolation are examples of social disadvantages which negatively affect health.

6-2 Why might the socially disadvantaged have poorer health?

Possible reasons include:

The field of socially determined health focuses on these last 3 factors (stress, health behaviours and discrimination).

6-3 How does the stress response lead to disease?

When people are worried about money, violence and their children’s futures, their bodies produce stress hormones, mainly cortisol from the adrenal glands and nor-adrenalin from nerve cells. Although this stress response can be useful in the short term to escape from danger, after months and years it has health consequences and leads to an increase in blood pressure and blood sugar, vascular disease such as heart disease and stroke, reduced immunity and premature ageing. This explains why even those conditions that were in the past considered as “diseases of affluence”, like diabetes and heart disease, are more likely to cause early death in poor communities.

Chronic stress results in physiological changes that increase the risk of diabetes, heart disease, stroke and reduce immunity.

There is good evidence to suggest that poverty causes certain patterns of behaviour that can both reinforce poverty and affect health. Importantly, it seems that the poorer you are, the less optimistic you are about the future.

Given the choice between having something enjoyable now or later, most people are likely to choose benefits in the present rather than the future. However sometimes people choose present enjoyment even when the future benefits of a different choice are greater. For example:

The behaviour of choosing what gives immediate pleasure even when a different choice will give greater benefits in the future is known as “present bias”. People living in poverty are more likely to have a present bias. The reasons for the link between poverty and present bias are not clear, but it is important for clinicians to realise that the poor should not be blamed for behaviours based on present bias.

Health economists also call present bias “excessive time discounting”. The reasons why the disadvantaged show greater present bias or excessive time discounting are unclear, but it is thought to be related to the cortisol response or to depression or to a combination of these. Another important factor is early schooling, which some people argue helps the brain to develop the will power, and to place more value on the future.

Poverty has a negative effect on decision making and often leads to “present bias”.

6-5 How does present bias affect the use of health services?

People who have a present bias are also more likely to put off a task that needs to be done until a later date or time, meaning that the task can end up never getting done, or being done too late. This is known as “procrastination”.
It is one reason for people not attending clinic appointments or not taking their children for immunisations. We can affect the way people make choices and make it more likely for them to do the right thing for their health by offering small incentives and making it as quick and easy as possible for them to get the services they need. This encourages them to “do the right thing”.

Health choices can be influenced by small incentives and by making “doing the right thing” easy.

Disordered environments where there are high levels of crime, violence and fear are associated with poor health regardless of income levels. This is probably also mediated by the physiological response to chronic stress. It is becoming more evident that children exposed to violence or abuse are more likely to become adolescents and adults who are less trusting of the healthcare system, less likely to be adherent to treatments and more likely to misuse drugs and alcohol.

Work can be good for health when:

Work can be bad for health when:

Employment has many physical and emotional health benefits.

Unemployment results in poorer health. This is partly because there is less financial security. However, even in countries with very generous unemployment benefits, the unemployed have worse health than people who are employed. This is probably because of the loss of other work benefits, such as self-esteem.

Worse health is also seen in people with job insecurity, and those who are underemployed (involuntary part time workers, those who have skill levels above the work they are doing, and those on very low pay). However, in this case it may also be that the less healthy get worse jobs. Unemployment commonly leads to episodes of depression and stigma.

6-9 What is stigma?

Stigma means a strong disapproval of certain people or diseases. Behaviours, lifestyles and certain diseases such as mental illness can be stigmatised. Diseases are usually stigmatised when there is fear and a lack of understanding, which means that the patient is blamed for their condition. When this happens:

Stigma is often associated with HIV and other sexually transmitted diseases, teenage pregnancy, alcoholism, and being overweight.

Stigma is disapproval of a person who is different to you

6-10 What can be done about stigma?

When a disease is stigmatised, people may not seek care so healthcare providers may need to be more pro-active about finding cases. Stigma tends to be more common in neglected and undertreated illnesses such as mental health problems. There is evidence that stigmatisation is reduced when information and effective treatment become available. Community education can reduce stigma as has been seen in people living with HIV.

Case study 1

Mrs Apollis is a 47-year-old widow. She rents an informal house on somebody else’s property in a low income area and does casual work filling shelves at a local supermarket when she is needed. She currently has loans for her television, microwave oven and some furniture that she bought when she had more regular work. Her son is addicted to “tik” (crystal meth). He lives at home, is unemployed and threatens her when she does not provide him with money.

1. How does Mrs Apollis’s social environment put her at risk of chronic disease?

Mrs Apollis is living in a situation of high stress with an uncertain income, financial commitments and concern about her son’s behaviour. The chronic stress response will likely lead to high blood pressure, high glucose and reduced immunity that put her at risk of conditions such as diabetes, heart disease and infections.

Case study 1 continued

Mrs Apollis visits the local clinic feeling unwell and is told she has high blood pressure. She is started on medication that brings her blood pressure under control. Several months later, she attends the clinic once more but her medication is out of stock. She is asked to come to the clinic again at the end of the week. She fully intends to visit the clinic, but there is some work for her at the shop on Friday and her son is arrested on Saturday. The clinic visit gets put off and she defaults from treatment. Six months later, she is admitted to the casualty department with a severe stroke. Her blood pressure is 240/130mmHg (very high).

1. What is the most likely reason that she defaulted from treatment?

Her social circumstances put her at risk for “present bias”. It is likely that her clinic visit was put off because she had the opportunity to earn money and deal with her son’s situation. The fact that the medication was out of stock the last time she visited and that there would be stock when she visited again would have informed her decision as well. In her social and economic situation, the clinic visit was less of a priority.

Case study 2

An organisation working in India found that mothers given a 1 kg bag of lentils when they attended a clinic were twice as likely to bring their children for immunisation as mothers who did not receive lentils.

1. Why did such a the bag of lentils (a small incentive) make such a big difference?

The bag of lentils is a form of food security and was just enough to swing the choice of some mothers so that they decided it was worth the effort of taking their children for immunisations. Health providers are starting to learn how what seems to be small incentives can be used to encourage good health behaviour.

Unit 7: Migration, urbanisation and globalisation


By the end of this unit you should be able to:

7-1 What is migration?

Migration is the movement of people to make homes in new places. It can be a temporary move, for example looking for seasonal work, or it can be with the intention of settling permanently. A migrant’s links with their former home (or “sending” community) may remain strong, or may be partially or completely lost.

7-2 What is international migration?

International migration is migration between countries. Most international migrants are either fleeing conflicts or seeking better opportunities.

7-3 What is internal migration?

This is migration within a country. Internal migration is most commonly from rural (country) to urban (town/city) areas. This form of migration is very common in South Africa. It may be permanent but is often seasonal.

Moving from a rural to urban area within a country is a common form of internal migration.

7-4 What causes local movement of people in urban areas?

People living in low-income urban settlements tend to move frequently. This is because many people rent living space and do not have easy access to legal protection against being thrown out of their homes (no secure tenure).

7-5 What drives migration?

There are many reasons why people migrate. They can be thought of as “pull” factors that attract people to new environments, and “push” factors that make living in the old environment difficult.

7-6 What are common pull factors?

Common pull factors include:

Employment, education and healthcare are important pull factors in migration.

7-7 What are common push factors?

Common push factors include:

Conflict and difficulties making a living in rural areas are common push factors in migration.

7-8 What are the health risks of migration?

The health risks include:

There are many health risks to both international and internal migration.

7-9 What is an informal settlement?

In an informal settlement residents have often erected their own housing, and services, particularly water and sanitation, have not kept up with the population increase. The residents of these communities are particularly vulnerable to diseases related to overcrowding, and poor water, sewage and sanitation, while access to healthcare may be limited.

New arrivals will often not have employment and may stay with extended family or friends while looking for work. This contributes to overcrowding and places additional demands on the breadwinner in that household. Unemployment and the loss of strong social ties make crime more likely and the residents of informal settlements often report living in fear.

Informal settlements are usually overcrowded and dangerous with poor water and sanitation services.

7-10 What is a megacity?

The move to urbanisation has caused cities to grow rapidly, and join up with other urban areas. A megacity is defined as a city with over 10 million residents. Of the 10 largest megacities worldwide, 7 are in low- and middle-income countries. Johannesburg, Cape Town and Durban are approaching the size of a megacity.

7-11 Is urbanisation a bad thing?

No. On the whole, urban populations have better access to education and health services and live longer than rural populations. Urban environments also provide work opportunities that can drive economic growth. Families in urban areas have fewer children.

7-12 Why do the health figures of urban areas look good when many people living in urban areas have poor living conditions?

When health statistics such as the under-5 mortality rate, or access to a skilled birth attendant are compared between urban and rural areas, the urban statistics are almost always better. This is partially because health services are better in urban areas. However it is important to bear in mind that health and opportunities can vary dramatically within towns and cities. Health and health outcomes in some informal settlements may be worse than for rural populations. Where possible, the overall health figures for a city should be “unpacked” so that problems in some urban communities, particularly townships, are not hidden.

7-13 What is globalisation?

Globalisation refers to the way in which countries around the globe are increasingly interconnected. There are 2 components of globalisation:

As a result of globalisation many speak of the world being a “global city” with common opportunities and problems.

7-14 What are the positive health and social effects of globalisation?

Positive effects include:

7-15 What are the negative health and social effects of globalisation?

Negative effects include:

Overall, although globalisation means that goods are more widely available, there is strong evidence that it increases inequality, good evidence that it limits the scope of social policies and serious concern about its contribution to the global spread of disease.

There are health benefits and health risks associated with globalisation.