Chapter 2 Determinants of Health and Health Inequities

Determinants of Health and Health Inequities

After completing this chapter, the reader will be able to:

a. Income and social status
b. Social support networks
c. Education and literacy
d. Early child development
e. Social and cultural environments
f. Physical environments
g. Employment/working conditions
h. Health services
i. Gender
j. Health behaviours

Linking these topics to the Medical Council exam objectives, especially sections 78-1 and 78-3.

Note: The colored boxes contain optional additional information; click on the box open it and to close it again.
Words in CAPITALS are defined in the Glossary

Peter Sulawesi’s environmental asthma

Ms. Sulawesi is consulting Dr. Rao yet again for Peter, her three-year-old son. They live in a damp and poorly heated apartment above a dry-cleaners; Peter has had three emergency room visits in the past month for poorly controlled asthma. Ms. Sulawesi is a single mother who recently immigrated to Canada with no family and few friends here. She works as a cleaning lady in the local school, in the evenings and on weekends. Dr. Rao tried involving social services, but they are overwhelmed with more pressing issues. The landlord refuses to make repairs to the apartment and winter is approaching. Dr. Rao’s immediate task is to treat the asthma symptoms, but he is fully aware that this will do nothing to correct the factors that will likely continue to exacerbate the asthma. He talks to his practice nurse whose sister may be able to rent Ms. Sulawesi a better apartment for an affordable price. Dr. Rao feels pleased that he has advocated for his patient but recognizes that he cannot address the underlying cause. Someone else will move into the damp apartment, likely creating another chronic case. Perhaps he should notify the local public health department …

Effective disease management requires attending to the patient’s immediate problem, then tackling any modifiable factors that gave rise to the condition – in Peter Sulawesi’s case, his dilapidated and perhaps mouldy living environment. The goal is to avoid a revolving door cycle of repeat symptomatic treatments for the effects of an enduring environmental cause. The CanMEDS clinician roles introduced in Chapter 1 blend  care for individual patients with interventions to address determinants at the community and population levels.

Public, and Population Health

Dr. Rao works in a primary care system that operates alongside public health and social service systems designed to address contextual factors that exacerbate illnesses such as Peter’s asthma. The public health system focuses on preventing disease and protecting health (See HEALTH PROTECTION in the Glossary). “Public health is defined as the organized efforts of society to keep people healthy and prevent injury, illness, and premature death. It is a combination of programs, services, and policies that protect and promote the health of all Canadians.”Unfortunately, this definition does not specify what public health actually does. Unlike other branches of medicine, public health does not address a particular type of disease or therapy, but employs a variety of approaches to address whatever population health issues are most pressing in each place and time. As patterns of disease evolved historically, public health went under  a succession of names as it wrestled with whether environmental factors, or individual behaviour, or social problems should form the main target of interventions (click on Nerd’s corner “Evolution of thinking”).

Evolution of thinking about public health

As new patterns of disease unfolded during the twentieth century, public health actions changed to keep pace, and this was reflected in changing names for the discipline. The earliest approach, termed “public hygiene”, focused on environmental sanitation. Then, between 1920 and 1940, the development and mass application of vaccines encouraged a shift toward “health protection”. During the 1950s the importance of the social environment was formally recognized and university departments were named “community health,” or “community medicine” to emphasize the role of doctors. As diseases of lifestyle became more prominent in the 1960s and 1970s, attention shifted towards changing behaviour and “health education” was born, subsequently broadened to “health promotion” in the 1980s. The health promotion movement recast the role of individual people, who moved from being passive recipients of health education to active participants encouraged to assume responsibility for their health, mainly through lifestyle improvement. National programs and policies promoted exercise, good nutrition, safe drinking, and smoking cessation. In the 1980s the healthy cities movement focused attention on the built environment (promoting sports facilities, walking paths, pedestrian malls).

Meanwhile there was continued debate over whether traditional public health should be broadened to include health promotion, or whether it should retain a narrower focus on health protection. Critiques of health education argued that many people, especially those with limited resources, lack the opportunity to improve their lifestyles since they are constrained by their economic and cultural milieux. Health education risked “blaming the victims” of their circumstances (see “Blaming the Victim”, below), and focusing on changing lifestyles will not alter the circumstances that gave rise to these behaviours. Behaviours were increasingly recast as symptoms of underlying social determinants, rather than as central causes of poor health. This gave rise to the population health perspective, which highlights the need to modify underlying social determinants of health.

Blaming the victim

The phrase “blaming the victim” was coined by the American psychologist William Ryan in 1976. He criticized an earlier report on black families in the U.S. that had attributed their enduring poverty to their culture and behaviour patterns, rather than to the structural conditions of society that constrained their choices. The issue of blame is relevant in thinking about how clinicians can deal empathetically with patients whose illness is related to their lifestyle (smoking, lack of exercise, alcohol abuse). It may be impossible to determine how far a patient’s lifestyle is a matter of personal choice versus social pressures and constraints. A superficial analysis suggests that obesity arises from poor dietary choices, but these choices are constrained by food availability, affordability, and by the person’s social environment in ways largely unknown to the clinician. The challenge is to help patients martial the resources to overcome their problems while being realistic about their capacity to modify behaviour, and on their even more limited capacity to control their environment.

The tendency to “blame the victim” also reflects a belief in a just world: if we believe that good behaviour gets rewarded, then bad things like a cancer should simply not happen to a good person. Scientific advances should tame randomness. Hence it becomes logical to attribute at least some blame to the person who is suffering. And this tendency increases as we learn more about risk factors: this patient likely wouldn’t have bowel cancer if he had eaten enough fruit and veggies; that one might not have diabetes if she had exercised enough.

Many public health interventions have been outstandingly successful, most notably in controlling infectious diseases that have an identifiable single link in their causal chain that can be broken, for example by an immunization, or by improved sanitation. But recent challenges such as the obesity epidemic prove more intractable: the link between diet and body weight is complex; weight gain can be remarkably hard to reverse, and powerful business intrerests promote inappropriate diets. Intervention is required on several levels: individual counselling, creating supportive environments, and broad policy changes to modify the affordability of healthy foods. Coordinated interventions of this scope are the hallmark of the population health approach. This holds that, while encouraging individual responsibility for health, we must also address underlying social determinants, such as poverty, that constrain people’s ability to achieve real gains in health.

The concept of population health gained prominence in the 1990s; it overlaps with public health. Both are concerned with patterns of health and illness in groups of people rather than in individuals; both monitor health trends and examine their determinants; both propose interventions at the population level to protect and promote health and both propose ways to deliver these interventions. The distinction is subtle, but the population health approach is seen as broader, as forming a unifying paradigm that links disciplines from the biological to the sociological. It proposes a rational basis for allocating health resources that balances health protection and promotion with illness prevention and treatment, while also making a significant contribution to basic science.2 Dr. Christina Mills, past president of the Canadian Public Health Association, quipped “Population health is how we think, public health is what we do” (quoted by Hancock3). To illustrate: a public health approach to tackling childhood obesity might design education programs for parents and children, advocate for subsidized healthy school lunches, for banning sweetened drinks in school vending machines, and lobby for tougher regulations on marketing junk food to children, and to promote physical activity, etc. A population health perspective might extend these approaches by raising awareness of the food system itself: how do import tariffs and agricultural policies affect the price of food and how might they be improved? Could city planning policies overcome the problem of urban food deserts where people without a car lack access to a grocery store? (See the box on “An organic view of population health”). Population health still values personal health as a key outcome, but views issues from a broader perspective that includes economics, environmental sustainability, social justice, etc.

Population health

John Frank (founding director of the CIHR Institute for Population Health), 1995: “Population health is a conceptual framework for thinking about why some people, and some peoples, are healthier than others – the determinants of health at individual and population levels. The major determinants of human health status, particularly in countries at an advanced stage of socio-economic development, are not medical care inputs and utilization, but cultural, social and economic factors – at both the population and individual levels.”

Kue Young (author of a leading textbook on population health), in 1998: “A conceptual framework for thinking about why some people are healthier than others, as well as the policy development, research agenda, and resource allocation that flow from it (…) Population health studies serve the objectives of describing the health status of a population, explaining the causes of diseases, predicting health risks in individuals and communities, and offering solutions to prevent and control health problems. To achieve these aims, population health requires collaboration between the core science of epidemiology, several social sciences which are also concerned with population phenomena, the humanities, and laboratory-based biomedical sciences.” 2, p4

These ways of thinking give rise to strategies to improve health, as described by Health Canada in 1994:

“Population health strategies address the entire range of individual and collective factors that determine health. Traditional health care focuses on risks and clinical factors related to particular diseases. Population health strategies are designed to affect whole groups or populations of people. Clinical health care deals with individuals one at a time, usually individuals who already have a health problem or are at significant risk of developing one.” 5

Note that you may hear the term “population health” used in a purely descriptive manner, referring to “the health of the population, measured by health status indicators.”6 This usage does not refer to the population health perspective, which is the focus of this chapter.

An organic view of population health

A population is normally defined in geographic terms as the people living in a neighbourhood, city, or country. Alternatively, a population can be defined by any characteristic of interest that a group of people shares in common, such as age (as in Gen Z), socio-economic status, language, or lifestyle. Here, population health is measured by aggregating measures of individuals, such as prevalence or incidence of disease or life expectancy, that record health in the population.

By contrast, an organic view of a population focuses on the functioning of the population as a whole: as something more than the sum of its parts, a collective organism whose members act as a self-aware group, with shared values and traditions. For example, a healthy population or community might be one that works as a group to address challenges and promote the welfare of its members, and the population health perspective analyses the health of the population.7 A healthy population might rally to a natural disaster with a collective response that thereby contributes to the health of its members. In this perspective, indicators of a healthy population might include the existence of social equity legislation or the development of public policies that characterize a “caring society.”

This organic view has expanded the health promotion approach into a hybrid sometimes termed population health promotion. Many public health units now follow this approach and develop programs to enhance the ability of community groups to work together for the improvement of their own health.

Although physicians treat individual patients, they should be aware of the population perspective for several reasons. First, the old chestnut that “common things occur commonly” is true: your patient’s condition is a symptom of health patterns in the population, so knowing the population prevalence will influence the hierarchy of your differential diagnosis. Chest pain in a 50-year-old is more likely to be of cardiac origin than the same complaint in a 15-year-old. Second, your patient’s lifestyle may have caused his medical condition, but the driving forces for his lifestyle lie in his social circumstances. Your efforts to help him change health behaviours will often be frustrated by the social and environmental constraints he experiences. It may be more efficient to tackle a disease at the population level (e.g., by lobbying for taxation on high-fat foods and using the proceeds to subsidize fruits or exercise programs) than by treating large numbers of individuals (see Chapter 8).

Reflecting a population health approach, the CanMEDS physician roles include health advocacy: “As Health Advocates, physicians responsibly use their expertise and influence to advance the health and well-being of individual patients, communities, and populations”.8

Peter’s asthma – continued

Dr. Rao notifies the public health department of his concerns over young Peter Sulawesi’s condition and his suspicion of its environmental cause. But public health advises Dr. Rao that the possibility of mould in the apartment is really a personal matter between Ms. Sulawesi and her landlord or the local housing authority, but they do agree to send an inspector to see whether fumes from the dry cleaning business downstairs could be a public health hazard.

Ms. Sulawesi is unlikely to be able to move to a better apartment. She lacks the education to qualify for a better paying job and afford the higher rent. And the depressed local economy makes the landlord unlikely to spend money on renovations.

In general, public health is mandated to focus on the broader physical environment, including chemical or biological exposures that may exacerbate Peter’s condition. This seems ineffectual in this case. The population health perspective views Peter’s asthma as an example of a much wider pattern of remediable health inequalities between social groups. Might this offer a route to improvement?

Health Inequalities

In every society there are variations in health, whether between individuals, groups of people, regions or between countries.9  Indeed, most diseases and health states occur in predictable patterns. To illustrate, Figure 2.1 shows life expectancy in Canada plotted by sex and income.10, 11 The data were taken from a study of 2,734,800 Canadians who were followed for 15 years after the 1991 census. Deaths during that time were linked back to income information recorded on the 1991 census. Income was adjusted according to the size of the family that depended on it, to give a better indicator of income adequacy. The result is shown grouped into five categories (or quintiles) of income, running from poor (coded as 1) to rich (coded as 5). The vertical bars show the years of life remaining, on average, to a 25-year-old person in each sex and income category.

Income adequancy quintiles
Figure 2.1: Remaining life expectancy at age 25 in Canada by sex and income quintile, non-institutionalized population, 1991 to 2006

The results show troubling disparities in health: men in the lowest income category can expect to live about 7 years less than those in the richest category (48 versus 55 years beyond age 25); for women the contrast is about 5 years. Moreover, the deficit is not only for those with the lowest income: there is a steady rise or gradient in longevity across income levels and this pattern is called the “social gradient in health”.

This chart shows life expectancy, but rates of ill-health and disability also rise in a gradient as socioeconomic status declines, so poorer people experience the double deficit of a shorter life and a less healthy one. Such patterns are attributed to “social determinants” of health, defined as “the circumstances in which people are born, grow up, live, work and age.”12 Health gradients also occur across levels of education, occupation and residential area, all of which reflect socio-economic status as a social determinant of health. But note that the word “determinant” is not intended to imply inevitability or determinism; it comes from the Latin de termine, or “from the far end” (i.e., the origin) of a chain of causal influences.

Systematic variations such as those in Figure 2.1 should in principle be correctable: if richer people can live longer, there seems no inherent reason why poorer people could not live equally as long. A disadvantage that is correctable or could have been avoided is termed a HEALTH INEQUITY, carrying the implication of unfairness and moral unacceptability. “Reducing health inequities is an ethical imperative. Social injustice is killing people on a grand scale…  The conditions in which people live and die are shaped by political, social, and economic forces.”12 A leading example of health inequity in Canada is the health of Indigenous peoples, as shown in the Nerd’s Corner box, below.11

Terms for contrasts in health states

“Health disparities” or “health inequalities” refer to systematic differences in health status that occur among population groups. The terms disparities and inequalities are broadly equivalent although, as Marmot observed, disparities is the term more widely used in the United States while inequalities is used in Britain,13 so Canadians can use either!
Whichever term is used, it is unrealistic to think that we can remove all forms of inequality, so priorities need to be set, and a useful concept here is that of health inequity. “Health inequity” refers to those inequalities in health that are deemed unfair or that stem from some form of injustice. Inequities form a moral incentive for corrective interventions. On a global scale, historic inequities between nations persist in part because of the exploitation of developing countries by developed ones. Commentators in rich countries may refer to these contrasts as disparities rather than inequities, perhaps to downplay the urgency of working to resolve them.

Health inequities among Indigenous peoples in Canada

Most health indicators for the Indigenous peoples of Canada have shown clear improvements over the past 20 years, and yet they lag behind equivalent statistics for the population as a whole. A description of the challenges in assembling data on Indigenous health is given by a Statistics Canada report.14 Here are some highlights (percentages have been rounded):

  • Life expectancy at birth has improved among First Nations populations. In 2000, it rose to 68.9 years for males and 76.6 years for females, an increase of 13% since 1980. A projection to 2017 anticipates 73 years for males and 78 for females, but this is still about 6 years shorter than the Canadian average for men and 5 years shorter for women.15
  • Life expectancy for Inuit people is lower, at 64 years for males and 73 for females.
  • In 2019 the Canadian infant mortality rate was about 3.7 deaths per 1,000 births; the IMR for First Nations peoples was 2.3 time higher, while the rate for Inuit was 3.9 times higher.
  • In 2003, the most common causes of death between ages 1 and 44 were injury and poisoning. Among children under 10, deaths were primarily due to injuries, but suicide and self-injury take over as the leading causes of death for youth and young adults. For people aged 45 and older, circulatory diseases were the leading cause of death. These patterns parallel the Canadian population as a whole.
  • With respect to suicide, First Nations groups up to age 65 are at higher risk than the Canadian population. The greatest contrasts with the overall Canadian rates are for females aged 15 to 24, and males aged 25 to 39, at approximately eight and five times the Canadian rates, respectively.
  • First Nations people experience an elevated burden of infectious diseases. These include pertussis (3 times higher than the national average), chlamydia (7 times higher), hepatitis A (5 times higher) tuberculosis (8 to 10 times higher) and shigellosis (almost 20 times higher). [Shigellosis is a common bacterial infection in developing countries and results from poor water quality and inadequate sewage disposal. These in turn reflect poverty and inadequate infrastructure].
  • The prevalence of diabetes is around 5% for the overall Canadian population. For First Nations living on reserve the age-standardized prevalence was 17% in 2009, and 10% for those living off reserve. Prevalence was 7% for Métis.
  • Based on self-reports, 18% of non-Indigenous Canadians had a body mass index of 30 or above in 2009; figures for First Nations were 40% (on-reserve) and 28% (off-reserve). Equivalent figures were 33% for Inuit peoples and 25% for Métis.

Health inequities derive ultimately from many historical and social determinants. But social inequities per se can also play a causal role. For example, a power imbalance between the genders in some African countries exacerbates the risk of HIV infections among women who are prevented from using protection or are forced into prostitution. Or, a person’s mental health may suffer because they perceive the unfairness of continued social exclusion. The following sections review some of the main social determinants of health, and then describe how these interact to damage health.

The Major Social Determinants of Health

Virtually any characteristic of a society can affect the health of its citizens, so could be considered a social determinant of health. To make this less daunting, agencies such as Health Canada and the WHO have identified key social determinants that deserve special attention (see the additional materials box). The following paragraphs summarize the impact of a selection of determinants from Health Canada’s list.

Major health determinants

For a summary of the evidence on the impact that selected determinants have on health, see the federal Public Health Agency of Canada website.

Public Health Agency of Canada list of health determinants16  World Health Organization list of actions to address social determinants of health17
  • Income and social status
  • Social support networks
  • Education and literacy
  • Employment & working conditions
  • Social environments
  • Physical environments
  • Personal health practices and coping skills
  • Healthy child development
  • Biology and genetic endowment
  • Health services
  • Gender
  • Culture
Improve daily living conditions:

  • Early child development
  • Urban planning
  • Fair employment & decent work
  • Social protection systems
  • Universal health care

Tackle the inequitable distribution of power, money and resources:

  • Make health equity a priority for all government sectors
  • Allocate resources to health
  • International regulations
  • Gender equity & empowerment
  • Good global governance

Measure and understand the problem and assess the impact of action:

  • Monitoring, research, training
A Saskatchewan family physician, Ryan Meili, gave a TED talk about social determinants of health and the political imperatives that derive from them.

Early childhood development

In treating a disease, a doctor intervenes to correct a process that often began many years earlier. The life course perspective extends the origins of a disease back to childhood, and even to exposures faced by the child’s parents.18, 19 Nutrition and stimulation in early life influence a child’s physical and emotional development; if the influences are positive they build resiliency; if negative, they increase vulnerability. Traumatic experiences in early childhood shape personality and have a lasting impact on how the person will view his world, how he relates to others, and how he interprets events. The impact of broken homes, chronic childhood stresses and so forth have non-specific effects, acting mainly to increase emotional vulnerability in adult life.19 The recognition of critical periods in early child development has led to the popularity of programs such as Head Start.

Income and social status

While Health Canada’s list of determinants combines income and social status, it may be helpful to unpack these. Social status includes both a person’s formal position in society (student, manager, retiree) and the subjective feelings of prestige that their position accords them. The prestige part may be relevant in understanding mental health, whereas for conditions such as an occupational injury the person’s formal position may be the most relevant. In part, social status is inherited, but is largely achieved through education and thence occupation. It is also influenced (to varying extents) by factors such as ethnicity, personality, and happenstance. Linked to all of these is a level of wealth, which affects the person’s range of lifestyle options.

It is virtually impossible to disentangle the health effects of each of these factors: in epidemiological terms, an example of CONFOUNDING. Ultimately, it may not matter: whichever marker of social status and whichever health indicator is used, there is a universal tendency for those in higher social positions to enjoy better health. Exceptions are rare and often reflect the working of other factors: for example, elevated breast cancer rates among higher income women probably occur not because of wealth but due to delayed first pregnancy linked to establishing a career. Some other examples of an inverse gradient are transient and reflect social change. An example occurred when heart disease was increasing in the 1930s, and cases often occurred in richer people who could afford a cardiogenic diet and sedentary lifestyle. Subsequently, the decline in heart disease occurred more steeply among richer and better-informed people so that the familiar inverse income gradient now holds.21

The health impact of income, especially insufficient income, may be described in relative or absolute terms, and can relate to individual income, or to society as a whole (gross national income). Absolute poverty refers to lacking the resources to meet basic needs for shelter, nutritious food, clothing, and education; a poor person cannot afford choices that promote good health. In low-income countries, their absolute poverty and the resulting lack of infrastructure form the fundamental health determinant. In the initial stages of economic development, population health status improves rapidly as national income rises to the level where basic necessities (food and shelter) are available to virtually all (see the “International disparities in health” box). But there is a limit beyond which increasing wealth cannot further improve health, whether for an individual or a nation. Instead, overall health in richer nations is influenced more by the evenness of distribution of income within society, or income inequality: a marker of the range of incomes across the different levels of society. In two societies that no longer suffer extremes of poverty, the one with a narrower spread of incomes around the overall average will have greater longevity.22 

International disparities in health

As of 2022, Canadians could expect to live almost 83 years on average, a figure similar to that for France. Citizens of Japan and Singapore outlive us at 86 years, as do Australians (84.3 years), while Americans had a life expectancy of 80 years on average, placing them in 54th place in one international ranking. The disparities between nations are striking: women in Japan live 86.7 years on average, 25 years longer than women in Sierra Leone, Botswana or Swaziland.

Among the poorest countries, longevity increases rapidly with growing national wealth, as illustrated in Figure 2.2, below. However, as shown in the figure, beyond a Gross National Income of around $30,000 US per year, gains in life expectancy flatten, although there remains variability in longevity between countries. Beyond roughly $30,000 GNI, further improvements in health appear to derive more from the way that incomes are distributed within societies than from increasing the overall GNI. This was beautifully described in a brief video by Hans Rosling:

figure 2.2 Life expectancy and gross national income per capita, 2012-2013 (Statistics from the WHO and World Bank reports).
Figure 2.2 Life expectancy and gross national income per capita, 2012-2013 (Statistics from the WHO and World Bank reports).

Sources: Life expectancy Wikipedia
World Bank: Gross national income per person

Discussion Point: How could you explain the pattern shown in the graph in your own words?

What are the mechanisms for this? In every society there are rich and poor, and the richer have better health (Figure 2.1). As wealth improves, so does health, but with the ceiling above which more wealth cannot further improve health. Meanwhile, poorer people lag behind in health, pulling the national average down, so redistributing wealth to them should raise the average health more efficiently than across-the-board pay increases. Hence in richer countries, the relative size and level of economic disadvantage of the poorer segments of the population (i.e., the extent of income inequality) becomes a better predictor of overall health than total national income. Countries that redistribute wealth via fiscal policies to poorer people tend to have better overall health.22 This association between relative poverty and health is termed income inequality in health (see HEALTH INEQUALITY in Glossary) and has been widely discussed.9, 17, 23-25

At the level of treating individual patients like Paul Richards (whom we met in Chapter 1) there may be local agencies to assist the clinician – see the following boxes.

Paul’s continuing woes

Another of Dr. Rao’s patients, Paul Richards, continues to have difficulty. Six months ago Paul had a mining accident that prevented him from working and he has since developed angina. It seems unlikely that he will ever find another job because most of the desk jobs on offer require people with more education than he has. Money is tight; his disability pension is inadequate. Paul and his wife Julie rely on a wood stove for heating their house in winter because wood is free as long as Paul collects it himself – difficult because of his injury. The food bank, which they use regularly, mainly provides processed foods that are high in carbohydrates or fat and salt, so healthy eating is a problem.

Working with patients in poverty

Many health agencies are designed to deliver care to poor people. For example, Community Health Centres (CHCs) in Ontario often treat uninsured and homeless people, creating an atmosphere in which they can feel at ease. CHCs are staffed by medical and social services teams that include physicians, nurse practitioners, nutritionists, social workers, and community outreach workers. They tailor programmes to the needs of their local clientele, and may provide interventions such as a harm reduction unit, workshops for recent immigrants, classes on cooking on a low budget, and so forth. Members of ethnic groups can often use the centre after hours for meetings and to arrange mutual support.

Education and health literacy

Education both results from and contributes to social position. The social position of a child’s parents influences her access to educational opportunities. The resulting education influences her employment opportunities and thereby income; it influences whom she meets and where she lives. All these indirectly influence her health. Dementia offers an example. Here, limited education may lead to careers that expose a worker to neurotoxic substances that damage brain function. Conversely, higher education, and the stimulating career it may lead to, may build complex neural networks that create brain reserve and protect the aging brain against cognitive decline.26  Education also affects a person’s ability to navigate the health care system, to interpret health information and to communicate effectively with health professionals.27, 28  “Health literacy” refers to the patient’s ability to understand health information and to follow treatment guidelines. Several sources suggest that between 50 and 60% of Canadians lack a level of literacy that enables them to negotiate the health care system effectively, to follow written health advice, or to access and interpret lab results on their electronic chart.27, 29 Physicians need to bear in mind that our increasingly complex health system places high demands on the reading and problem-solving skills of patients.

Social support networks

Ms. Sulawesi lacks a supportive social network. No-one else in her town speaks her native language and she feels alone in a strange place. Social connections benefit health in several ways. They offer a source of emotional reassurance that helps a person cope with adversity. Networks can provide information, advice and practical support, such as knowing someone who can assist in a time of need. They can also support people during the process of changing health behaviours. People with strong social ties, who belong to clubs or organizations, who both give and receive assistance or who volunteer, report feeling healthier than others.30 A TED talk showed how a physician gained insight into the social networks of his patients.

The association between social connections and health also holds at the population level: communities that establish collaborative networks are resilient and better able to address social and economic challenges, so can be seen as more healthy. SOCIAL CAPITAL refers to a resource that derives from people’s willingness to cooperate and engage in collective action; this willingness in turn reinforces trust and confidence within the network. Neighbourhood watch programmes are an example. By contrast, low social capital is characterized by suspicion and hesitation to collaborate with others; this may occur where there are wide disparities in income and a perception of social inequalities. Various studies have linked higher social capital to reduced all-cause mortality25 and to greater well-being, better care for children, and lower crime.31 

Employment, working conditions, and occupational health

The WHO recognizes fair employment and decent work as a cornerstone of health, and advocates for fair minimum wages, full employment, and occupational health and safety standards.17 Although Canada’s overall unemployment rate may be low, at 6 or 7%, this masks wide variations. There are inequities between regions and across population groups – 11.5% of recent immigrants are unemployed and many more are underemployed.32

The health consequences of unemployment have been extensively studied and reveal complex relationships. Overall, people who lose their jobs experience reduced self-perceived health and increased mortality, but the effect varies by age, gender, and education.33 The health impact also varies according to the general unemployment level: where many individuals lose their jobs the health impact appears less severe.34 The concept of stress describes the main channel through which employment and unemployment influence health.

Stress and strain

Work stress (see WORK-RELATED DISEASES in the Glossary) derives from the demands work places on a person, modified by their perceived control over these, their work satisfaction, perceived levels of physical risk, and job security. Unfortunately, stress and the resulting strain are often not distinguished in the health literature, where stress can refer both to the input (the “stressor”) and the outcome (the resulting condition). These terms are distinguished in engineering, where stress refers to the load placed on a structure and strain refers to its resulting distortion. This offers a convenient metaphor for illness, and it would seem helpful to retain this distinction.

Work stress refers to high expectations at work, often accentuated by a worker’s low level of control over their work (see Definitions box). Demands that exceed the person’s coping ability result in feelings of strain, perhaps also in somatic disorders such as hypertension, peptic ulcers, migraine headaches and others. These affect many Canadians, especially women.35 Working conditions may correlate with other determinants, such as income, so that the lowest income households typically report higher levels of work stress due to job insecurity and dissatisfaction, with adverse effects on physical and mental health.36 Work strain can arise from a combination of high psychological demand (such as being pressured to work fast) while also having little freedom to make decisions affecting the job (e.g., being in a subordinate position).37 Strain also results from a mismatch between work effort and reward: jobs that demand high effort for low gain produce feelings of exploitation that predict poor health.38 A study that followed 10,000 British civil servants over 10 years showed that those who had little control over their work environment had an increased risk of subsequent heart disease.39 Reorganizing the workplace to provide a greater variety of tasks and more decision-making authority at work may decrease risk.

A lack of control over working conditions also increases the risk of workplace injuries, which form an important cause of disability and mortality in Canada. In 2020, 313 Canadian workers died due to injuries at work and a further 611 died from occupational diseases.40 There were over 253,000 claims for lost time at work due to injury; around 62% of these were for men.41 The lower a worker’s income, the more likely they are to experience a work-related injury.42 

Paul’s work history

As a child, Paul was not interested in school and had difficulty keeping up with his class. Nor did his parents see the value of schooling: there were solid jobs in mining that didn’t require academic learning. However, as global economic changes put the mining industry under pressure, company managers began taking short cuts around safety legislation. Paul worried that his job was insecure but he couldn’t see a way out; he had to work long and tiring hours, ignoring safety procedures. This was coupled with the physical and mental stress associated with high-risk work. At the end of a 12-hour shift he was carrying a heavy, awkward load; he fell and twisted his neck, resulting in the injury that put him out of work. Currently, he is unemployed and is receiving Worker’s Compensation benefits. While this may address some of his financial worries, it is not going to match the income he earned as a miner and his prospects for future employment are limited, further worsening his stress.

The strain of family duties: caregiving

Having a sick or aging relative often imposes unpaid work, especially for women. For caregivers who are also employed, work stress increases and job security may be harmed due to absences to care for their relative. The resulting loss of income affects the whole family. Several countries have introduced benefits for caregivers, such as the 2006 Canadian Compassionate Care Benefit under the Employment Insurance Program, which provides financial support for individuals caring for sick relatives.

The physical environment

Environmental influences on health can be positive or negative, and exist at all geographic levels, from global (climate change) to national and regional issues (the destruction of war; air and water pollution), to local issues such as Ms. Sulawesi’s mouldy apartment. The benefits of spending time in beautiful surroundings are universally celebrated (see box “Positive places”) but most research focuses on negative environmental influences. Contaminants in air, water, soil and food are associated with both communicable and non-communicable diseases. Climate change and the associated weather extremes increasingly affect public health: hyperthermia from extreme heat; burns from fires; injuries from extremes of wind and rain; social disruption from changing sea level; under-nutrition in poor areas due to the impact on agriculture; increased risk of food-, water- and vector-borne infections; and the changing distribution of vectors and infectious agents which may introduce disease to previously unaffected regions.41 Few communities will be immune and there are very few short-term solutions. Further information from a Canadian perspective can be found in reports from Natural Resources Canada.42, 43

Positive places

There are many examples of the beneficial effects of places on health. Hospital rooms with a view over a garden may speed recovery;44 feeling attached to place provides older people with a sense of self and security;45 gardening is therapeutic46 and contact with nature confers a wide range of health benefits.47

Air pollution in Canada

Environment Canada reports encouraging trends in air emissions. Emissions of sulphur oxides from refining and smelting in Canada declined by 93% between 1990 and 2020. Trends for nitrogen oxides, of which about half come from transportation emissions, fell by 69% over the same time period, with much of the decline occurring since 2002.
Carbon monoxide emissions declined by about 67% between 1990 and 2020. The chief source is transportation, for which tighter vehicle emissions standards have been effective. But carbon monoxide also comes from natural sources such as forest fires, which vary widely from year to year but will only increase with climate change.
Respiratory health is also influenced by total particulate matter (TPM) in the air. Industrial source TPM declined by 44% between 1990 and 2012, but industry forms only a tiny fraction of the overall problem: roughly 95% of TPM comes from “open sources” (dust from roads, agriculture, construction sites). TPM from these sources increased by 33% between 1990 and 2020, largely due to construction activity and summer driving on unpaved roads.

The active transportation movement seeks ways to encourage human-powered transportation (walking or bicycling rather than driving) to reduce pollution and promote physical fitness. Feasibility depends on design of the built environment such as the proximity of relevant destinations, perceived safety, street design, and also the natural setting, with parks or trails.50 North American preference for private motor transport remains strong; as people move further from the city centre they drive more, increasing the risk of vehicle collisions, as well as “higher rates of heart and respiratory diseases and obesity, and elevated stress related to both commuting among congested traffic and increased noise levels.”17 In rural areas where walking or cycling is impractical (and often dangerous because of road conditions) the prevalence of obesity is higher than in urban areas, and road traffic injuries are relatively frequent.

Individual and public health services

Innovations in health care have conferred immense benefits on health and longevity, especially in the developed world. Antisepsis, antibiotics and other pharmaceuticals, and life-saving surgical procedures have revolutionized the management of most diseases.

And yet the greatest impact came from public health interventions such as sanitation and communicable disease control measures, and from disease prevention (immunization, tobacco control measures, and screening).49 Basic engineering measures, such as protecting water supplies or reducing overcrowding in homes, often have the greatest impact on overall health. This was famously illustrated by the decline in tuberculosis in England and Wales. As Figure 2.3 illustrates, tuberculosis mortality had been declining for at least 100 years before the introduction of any effective therapy; this early decline was achieved by non-specific means such as improved housing and nutrition, and through specific legislative measures such as banning spitting in public to reduce disease transmission. Similar patterns of decline occurred for polio, smallpox, and whooping cough, all of which responded dramatically to improvements in hygiene long before effective medical treatments were developed.

Figure 2.3: The historical decline in tuberculosis in England and Wales, 1840–1970, showing the timing of critical discoveries in understanding the disease
Figure 2.3: The historical decline in tuberculosis in England and Wales, 1840–1970, showing the timing of critical discoveries in understanding the disease

Public health measures to improve air and water quality benefit all citizens, whereas the benefits of individual medical care are less evenly spread. Roughly four million Canadians do not have access to a family physician.52 Despite universal insured health care, access to medications, dentistry, home care, and home support are significantly affected by income. But even when financial barriers to care are removed, we run the risk of continued health inequities if programs are not accessible because of location, or because of a person’s feeling of discomfort at using facilities. Practitioners’ offices tend to be built in richer neighbourhoods, where property values will be preserved and quality of life for their employees is more attractive, but where the need for care is lower. Similarly, facilities relevant to promoting health, such as commercial exercise facilities, are less likely to be built in lower-income or immigrant neighbourhoods.5 There is an inherent tension between economic efficiencies, which lead to clustering specialized services in urban areas, and geographic access for people in rural areas. The greatest overall benefit for health may now come from improving access to care for disadvantaged groups: distance medicine for those in remote areas; community health centres for street dwellers, sex trade workers and people with addictions; family planning clinics for teenagers; and clinics tailored to multi-ethnic neighbourhoods, with staff members who speak minority languages and deliver culturally appropriate care.


Sex refers to our biological identity as male or female, whereas gender refers to the differential status, lifestyles and access to services that are linked to a person’s sex. It refers to “the array of socially constructed roles and relationships, personality traits, attitudes, behaviours, values, relative power and influence that society ascribes to the two sexes on a differential basis.”54

Women in contemporary Canada on average live longer than men, as seen in Figure 2.1, and yet women experience more morbidity. Biological differences between the sexes, earlier development of fatal conditions such as heart disease among men, along with gender differences in the distribution of other health determinants, contribute to these patterns.55 Nevertheless, several gender inequities remain, and largely as a result of the women’s movement these have received considerable attention. These occur in all societies in terms of differences in power, freedom, resources and values, inequities that may affect health. The most egregious examples include the exploitation of women in the sex trade, underage marriage, or the work conditions in sweat shops in the garment industry. In developed countries there are often gender inequities in income, such that wages for women may be around 20% lower than those for men.56 Because single parents are almost always women, the lower income of women also affects their children.17

Gender inequities in health do not only result from income disparities; gender is also linked to differential access to health services, to unequal obligations to provide unpaid family care duties, and to disparities in nutrition.23 Gender inequities also exist in health research: clinical trials historically have been more likely to use male experimental subjects and yet the benefits of many interventions vary between men and women.57, 58 For example, mortality due to cardiovascular disease is increasing in women, yet they are under-represented in research studies.59 Women present cardiac disease differently than men, and are less likely to be diagnosed accurately and to receive timely treatment. Given these disadvantages of being female, we have yet to fully explain why women live longer.22, p191 Part of the explanation lies in gender differences in risk taking, which in turn is linked to culture.


“Culture is a system of ideas, values, and metaphors that are consciously and unconsciously used or enacted by people in their everyday lives. It is not a rigid set of behaviour traits but a fluid and adaptive system of meaning.”60 Culture “explains what one must know and do to function in a given society.”61 Some related terms are shown in the definitions box.

Sharing and transmitting culture

Culture is learned and conveyed from generation to generation through the process of socialization. Parents transmit cultural values, but so do peer groups and schools. Young people often struggle to choose which cultural code to follow; they receive conflicting messages, perhaps contributing to adolescent rebellion and significant health consequences such as drug use. This tension may be amplified in immigrant families if the parents do not understand the adopted local culture.

Culture is not unitary. Most societies present a mainstream culture and various subcultures. These may be defined in terms of age (teen culture), lifestyle (gay culture), ethnicity (West Indian), location (street culture), or even health problems (drug culture, Alcoholics Anonymous). Most individuals belong to several cultural groups at the same time.

Race and ethnicity

Ethnicity is an imprecise term that refers to a collective identity based on a combination of race, religion or a distinctive history. An ethnic group shares cultural customs that distinguish it from neighbouring groups. Ethnicity differs from race in that the shared characteristics are values, norms and ideas, rather than physical characteristics. Ethnic groups are generally sub-groups within a culture or race. Ethnicity may refer to how a person describes him- or herself in terms of ancestry, history and culture.

Race is a quasi-biologically defined classification of people based on shared genetically transmitted physical characteristics: “A division of humankind possessing traits that are transmissible by descent and sufficient to characterize it as a distinctive human type.” Race is not a scientifically rigorous classification: there is a huge amount of mixing among races; characteristic racial features do not appear in all individuals, and there may be more genetic variation within a race than between races.

Racialized refers to the social process of of focusing on racial identity as the salient characteristic of a person or group, typically to marginalize and discriminate against them. This will often divert attention from real health determinants, such as poverty.

Multiculturalism refers to the recognition of, and support for, racial and cultural diversity in a society. It implies respect for the customs and beliefs of others and covers the right to equal opportunity and recognition regardless of race, colour or religion.

Prejudice is the holding of unfounded ideas (generally negative, but sometimes positive) about a group, whether a race, class or ethnic group. These ideas are resistant to change and are rarely open to logical discussion.

Culture filters the effect of other social determinants, affecting how groups of people react to their circumstances and environment. Our cultural background influences our beliefs, behaviours, perceptions, emotions, language, diet, body image, and attitudes to illness, pain or misfortune, all of which can influence health and the use of health care.62 Culture also underpins values–deeply held beliefs that define what is desirable and moral, and values influence expectations of behaviour, including the way a doctor’s actions are perceived by the patient. Dr. House of the t.v. series, transgresses numerous values of the medical profession. But although cultures may be shared, people are far from homogeneous, and we must never assume that all members of a culture will hold the same norms and values or will react the same way to new ideas and knowledge. Some errors and prejudices can be avoided by being careful to view culture as influencing behaviour within each specific context, rather than in general.62  Chapter 3 explores ways in which clinicians can incorporate cultural awareness into their daily practice of medicine.

Determinants and Risk Factors

The reference to a person’s culture as a filter for other social determinants of health introduces the idea of multiple steps in the chain of disease causation, running from the broadest social determinants through local environmental influences, to personal risk factors. A common metaphor of disease causation (and prevention) distinguishes between underlying or distal factors, such as a government policy mandating free immunization clinics, intermediate factors such as accessibility of local health care facilities, and proximal factors such as whether an individual obtains an immunization. An equivalent metaphor refers to upstream and downstream factors.

The upstream-downstream metaphor

This metaphor contrasts clinical and public health approaches; it imagines a dangerous river in which people have drowned. Following a clinical model, rescue workers work hard to pull victims out, but realize that no matter how hard they struggle they cannot rescue them all. They discuss how to recruit more staff, and maybe put up warning signs. By contrast, the public health approach recommends looking upstream to figure out why people are falling or jumping into the river in the first place. Perhaps that can be fixed, for example by building a bridge or installing a fence, or even (in a population health approach) by addressing the determinants of suicide attempts.

Key idea: Social determinants establish the broad patterns of health in groups or populations: they set the incidence rates of disease, but they do not identify which individuals will get sick. There will always be variability around the averages shown in a chart such as Figure 2.1: some individuals live longer than the average of their income group and others live less long. This variability within a group is most helpfully attributed to the balance of personal risk and protective factors – characteristics of the person, their biology, behaviour, or environment that combine to increase or reduce their risk compared to the group average. To explain an individual case we have to consider both the underlying determinants of disease incidence in the population that set the baseline risk for the group of which he or she is a member, as well as the individual risk factors that modify the base-rate for this individual, relative to the absolute risk in the group.

We may now extend the diagram of the NATURAL HISTORY of a disease from Chapter 1 to show a chain of causation, as illustrated in Figure 2.4. The chain is laid out over the lifetime of an individual:19

Figure 2.4: Disease precursors and clinical course
Figure 2.4: Disease precursors and clinical course

Although the terminology is inconsistent among authors, it makes sense to refer to an influence such as socio-economic status as risk factor when referring to an individual (Paul’s limited income has forced him to rely on chopping wood for heat, increasing his risk of a cardiac event) and as a determinant when the focus is on group processes (an economic downturn caused widespread unemployment in Paul’s community). Paul’s smoking is a personal risk factor but it was to some extent influenced by the pattern of smoking in the social group in which he lives – the group culture. That pattern developed in the context of more distal social determinants such as national policies governing tobacco – policies that in turn had economic and historical roots. As most of the modifiable risk factors concern individual behaviour, the following sections review explanatory models for health behaviours.

Triggers for Paul’s angina

Paul Richards first noticed his chest pain when he was collecting wood for the family stove. He didn’t think it was anything serious; he doesn’t feel old and he quit smoking—although he admits to having the occasional cigarette when he is with his friends: they all smoke, so it’s hard to refuse. His wife Julie had reminded him that his father died aged 62 of a heart attack and insisted that he consult Dr. Rao about it.

Given Paul’s family history, lifestyle and pattern of pain, Dr. Rao diagnoses mild effort-induced angina. He knows this is common in a person of Paul’s age and socioeconomic status. But Dr. Rao cannot modify these determinants, so they discuss the risk of the exertion involved in hauling lumber coupled with Paul’s smoking and overall lack of fitness.

Causes, risk factors and determinants

Reference to cause is most useful in speaking of an individual case, such as Paul’s angina. Causes typically operate in a chain or causal sequence, forming “the causes” for a case. They typically divide into underlying (or distal) causes, contributing and immediate (or proximal) causes. In clinical medicine, this can be interpreted as the etiological sequence. Smoking damaged Paul’s blood vessels; the damage means that his coronary vessels cannot react adequately to effort, so the resulting ischaemia causes his angina.

Determinants are generally applied in explaining patterns of health or disease in groups of people. Determinants operate at an earlier, upstream or distal level in the overall causal chain. They set the overall population risk. Determinants refer to the circumstances that produce proximal causes, so are often termed “the causes of the causes” of disease.

Risk factor is a broad term that carries some ambiguity. The intent is to refer to a factor that increases a person’s likelihood of a future adverse health state, but risk factors are neither causally necessary nor sufficient. Cigarette smoking greatly increases the chances of pulmonary disease, but lung diseases can arise for other reasons (so smoking is not a necessary factor), and many smokers do not get lung disease (it is not sufficient).

Risk factors also include variables that are not causal: they may simply be associated with the causal factor. Gender or increasing age may not themselves cause disease, but are associated with hormone levels that may. “Risk marker” or “risk indicator” are more precise terms to describe a correlate of a causal factor. Such markers are useful in identifying someone at risk but do not represent a suitable target for action to reduce this risk.

Personal health behaviours and coping skills

Many upstream social determinants influence health via personal behaviours, most notably smoking and other substance use, diet and exercise patterns. Health behaviour refers to actions that influence whether or not a person will become ill; illness behaviour refers to his reactions when he does, including whether or not he seeks care, then follows the doctor’s recommendations. Illness behaviour is influenced by social expectations, described by sociologists in terms of the “sick role”, which refers to society’s expectations for a person who is ill. Society permits the sick person to be exempt from his normal social roles but in return he is expected to try to regain health, partly by seeking competent medical care and following the doctor’s recommendations, including modifying health behaviours.63, 64

Clinicians generally find that altering a patient’s health behaviour is slow and difficult. In part this is because health behaviours are not solely a matter of personal choice, but are strongly influenced by social and cultural pressures so that change is most likely to result from changing social determinants (see box “Changing personal health practices”). In terms of motivation to change there is also the “tragedy of the commons” whereby we benefit from everyone else’s sacrifices (such as avoiding driving to reduce pollution) but suffer from our own. Psychology offers several theoretical models that describe the personal and contextual influences on health behaviour; these help explain why behaviour is often so hard to change. One of the earliest and best known is the Health Belief Model.

Changes in personal health practices

Smoking. Smoking is in decline in most industrial countries, the main exception being China. Canada illustrates this public health success story. The annual Canadian Tobacco Use Monitoring Survey reported a decline in the numbers of Canadians who “smoke daily or occasionally” from 25% in 1999 to 18% in 2008, then to 10% in 2020, despite important opposing pressures from the tobacco industry. Tobacco manufacturing is an important Canadian industry and production is actually increasing, with much of the excess being exported, contributing to international health disprities.65

Diet. The food we eat and our physical activity levels directly affect our body weight. About 65% of Canadian men aged 20 and over were overweight or obese (Body Mass Index or BMI > 25) in 2013, compared to 71% in the USA, 56% in France and 29% in Japan.66, 67 A high BMI, sedentary lifestyle and poor diet put people at risk of diabetes, cardiovascular disease, osteoarthritis, as well as other negative medical and social consequences. As with smoking, important social and commercial interests promote obesity. For example, healthier eating options are more expensive and often unaffordable for low-income families. Furthermore, salt, sugar and fat may be addictive in much the same way as nicotine; the addictive qualities of salt and sugar have allowed the food industry to seduce people into overeating.66

Exercise. The evidence that exercise benefits health comes largely from observational studies. The evidence from intervention studies is much less clear, in part because of the varied efficacy of behaviour change interventions, and in part because of the highly selected populations studied. This has complicated the incorporation of a clear exercise prescription into clinical practice; the available Cochrane Reviews for preventing various conditions show mixed results. Exercise recommendations are also affected by community design, as when people living in high-crime neighbourhoods avoid outdoor physical activities.

The Health Belief Model

The Health Belief Model (HBM) was proposed by G.M. Hochbaum in 1958 to summarize three key factors that influence whether or not a person will participate in preventive programs, originally in the context of tuberculosis screening:

  1. Does the person feel motivated to take action? This depends on how susceptible they perceive themselves to be to the disease in question, and by how severe they judge the disease to be (see Figure 2.5).
  2. How cost-effective do they judge the recommended action to be? Will it prevent the disease or at least reduce its severity? Are there psychological, financial, and other costs or barriers involved in the proposed action?
  3. There must also be some cue that triggers an actual change in health behaviour. This can be internal (e.g., development of symptoms) or external (e.g., a friend gets sick, or the doctor’s advice).68

Figure 2.5: Schematic outline of the Health Belief Model
Figure 2.5: Schematic outline of the Health Belief Model

How accurate is the Health Belief Model?

Janz and Becker reviewed studies of the predictive validity of the HBM, concluding that prospective studies supported its predictive validity. Perceived barriers to action appear to be the single best predictor of subsequent behaviour.69 Several studies have evaluated the HBM in predicting uptake of mammography screening, and it has been used in guiding the design of interventions to promote screening. Interventions that address the factors covered by the HBM tend to produce superior results, although other characteristics of the intervention not included in the HBM are also influential.70 This led to changes to the HBM, as seen in the Theory of Planned Behavior.

The Theory of Planned Behavior

Developed in the 1980s, Ajzen’s Theory of Planned Behavior (TPB) extended the HBM. Like the HBM, this assumes that health behaviour can be analysed in terms of rational planning,71 as summarized in the top line of Figure 2.6. But the theory also incorporates social and cultural influences via the idea of subjective norms: the person’s perception of social pressures to behave in a certain way (middle row of the figure). Subjective norms incorporate the person’s beliefs about how others view his current and proposed behaviours, and how much he values the opinions of his reference group. The third element of the TPB concerns whether the person feels capable of making the proposed change—his perceived behavioural control. This reflects his perceptions of barriers to the action and his confidence in being able to overcome such barriers, a notion that resembles self-efficacy.

Figure 2.6: Schematic outline of the theory of planned behaviour
Figure 2.6: Schematic outline of the theory of planned behaviour

How accurate is the Theory of Planned Behaviour?

An impressive body of literature supports the validity of the TPB, including several systematic reviews and meta-analyses of study results. For example, a 1991 meta-analysis found that the variables in the model explained 50% of the variance in behavioural intention (based on 19 studies) and 26% of variance in predicting actual behaviour (based on 17 studies).71 A 1996 systematic review concluded that 41% of variance in intention and 34% in actual health behaviour was explained by the TPB.72

In 2001, Armitage and Conner published a meta-analysis of 185 studies, giving a sample size of well over 300,000. Most of the studies were cross-sectional, but 44 longitudinal studies gave predictive validity evidence for behavioural intentions, and 19 studies predicted actual behaviour. The results are similar: roughly one-third of the variance in behaviour was predicted from the TPB model.73

These conceptual models remind us of the broad range of factors that influence health behaviour, illustrating why merely offering a patient advice is unlikely to be effective. But the models also suggest that the factors that do influence behaviour are logical, so health behaviour need not appear mysterious to the clinician. Most strategies for changing health behaviours, the obvious central interest for the physician, incorporate these factors, as described in Chapter 8.

Other terms applied to the influences included in these behavioural models mention predisposing, enabling and reinforcing factors. Predisposing factors include, for example, the person’s health awareness and attitudes toward health risks, and the social pressures on them to behave in a certain way. But these are insufficient to trigger change, and enabling factors support the actual transition to a new behaviour. An example would be an employer willing to sponsor an employee’s enrolment in a drug rehabilitation programme. But note that other enabling factors such as ready availability of drugs can also support continued behaviour. Reinforcing factors maintain the change process. Some are internal, such as improved feelings of wellness and the motivation this brings; others are social such as spousal support or monitoring by the physician, and others are environmental, such as no-smoking zones.

Putting it all Together: Interactions Among Determinants

We have described each health determinant and risk factor separately, but everyone is exposed to them in combination. Furthermore, determinants and risk factors interact, often reinforcing each other. Overcrowded housing promotes transmission of infection; this leads to time off work and hence reduced income, condemning people to live in overcrowded housing. The evolution of such factors over time is illustrated by young Peter Sulawesi’s situation (see box).

Peter Sulawesi’s prognosis

Dr. Rao continues to ponder the social determinants of Peter Sulawesi’s health: living in straitened circumstances and in sub-standard housing, the son of a refugee mother living in an alien culture. He is missing school for health reasons, which may contribute to poor school success, increasing his chances of remaining poor and continuing the cycle of poverty and ill-health.

Now, think through the social determinants for the case of Paul Richards. How would you judge his prognosis? How could Dr. Rao advocate for him?

In place of a causal chain, the complex associations among determinants and risk factors is often described as a causal web, conveying the idea of multiple causal pathways connecting outer, societal influences via intermediate layers to personal risk factors.74 Figure 2.7 illustrates a typical concentric model of social determinants, this one proposed by Dahlgren and Whitehead.75 Spanning national, community and individual factors, such models are generally described as social-ecological or eco-social models of health determinants in that they focus on the social environment.76

Ecology and ecosocial models

Ecology is the branch of biology dealing with relations between organisms and their environment, including other organisms. Oikos (transliterated as “eco”) is a Greek word meaning habitation, house or dwelling place.

Ecosocial models seek to integrate social and biological influences within their historical and ecological contexts to more fully explain the dynamics of health determinants. See, for example definitions by Krieger.77

Eco-social models are generic and apply to any health condition, so they typically do not illustrate the specific paths along which determinants lead to a particular health condition. Most determinants are, indeed, non-specific (a recession, poverty, lack of education) although some (such as alcohol or tobacco laws) target particular behaviours or diseases (see Resources box “Models of health determinants”, below).

Figure 2.7 Dahlgren and Whitehead conceptual model of the influences on health
Figure 2.7 Dahlgren and Whitehead conceptual model of the influences on health

Models of health determinants: particular or general?

There is debate over whether there can be a universal model of social determinants or whether models have to be specific to particular groups. This was discussed by Reading and Wein for Indigenous populations,78 and by Dyck for the Métis population. Dyck’s “Social determinants of Métis health” can be viewed at the University of Ottawa collection.

Detailed models of how determinants and risk factors interact have long been used in infectious disease. An example is the “epidemiological triad” which shows how a case of disease arises from an interaction between the person (or host), the disease agent (virus, bacterium or ingested substance, such as tobacco smoke), and an environment that both supports the agent and brings it into contact with the host: see Figure 2.8. Applying the triad model to a non-infectious disease, the immediate causal factor, such as an atherosclerotic plaque in a coronary artery, forms the agent.

Figure 2.8: The Epidemiological Triad of agent, host, and environmental factors
Figure 2.8: The Epidemiological Triad of agent, host, and environmental factors

This epidemiologic triad model is useful for explaining cases of disease after they arise, but (at least until genetic analyses become much more sophisticated) we cannot accurately predict which person will fall sick when exposed to a disease agent. We deal with this uncertainty probabilistically: risk factors increase the statistical probability that a person will fall sick (see PROBABILITY and LIKELIHOOD in the Glossary). The probabilistic language of risk is used because very few causes inevitably produce health consequences: factors such as host resiliency modify their effect. While traditional cultures often attributed this uncertainty to fate, astrology, or karma, we refer to random variation. As science increases our understanding of  disease, the random component has steadily declined (see Nerd’s Corner box “The role of chance”). The question of whether science will ever explain so much that we will be able to predict a patient’s time and cause of passing is one for you to ponder.

The role of chance in disease

Much of clinical practice involves navigating amidst uncertainties: what are my patient’s chances of developing a disease; how likely will he respond to this therapy? This uncertainty stimulates us to ponder the role of chance. Perhaps chance plays an inherent role in the development of a disease (but does God really play dice)? Processes that are inherently unpredictable are called aleatory chance or uncertainty (from alea, Latin for a die). Alternatively, chance can refer to cases of disease that we cannot yet explain given the limits of our current scientific understanding, and this we call epistemological chance.79

Factors yet to be discovered will presumably improve our understanding in the future, but how far can this go? There is optimism that genomics will enable more precise determination of future disease risk, but there are also arguments that genetic expression really has a stochastic or aleatory random component, making it impossible to predict at the individual level. Isaac Asimov explored this theme in his Foundation novels in the character of Harry Selden, a mathematician who developed psychohistory, which predicts everything, but only at a population level, leaving room for both individualism and predetermination.

Screening for a disease reduces epistemological uncertainty, since the disease is either present or not but we do not yet know which. But in answering a patient’s question about whether or not he will develop a cancer there is a mix: we may be able to refine the estimate of likelihood by collecting more information, but it can be cogently argued that there will always remain a degree of uncertainty, as we cannot anticipate all possible environmental factors in the epidemiologic triad that could act in future. A common clinical response to this uncertainty is to note that there can be no correct estimate of a patient’s future risk, but that he can make a personal and subjective estimate and act on that.

Modifying risk factors

Prevention targets modifiable risk factors, especially those whose effect on health is not conditional upon  other causal factors. Because of having a direct effect, such factors are often made the target of legislation. Other risk factors form part of a complex causal web, as with the effect of diet on coronary artery disease. Modifying only one such factor may not alter the disease outcome: the causal web holds up even when some strands are broken. Interventions to modify risk factors for cardiovascular disease can improve the risk profile, but this may have little impact on cardiovascular disease morbidity or mortality.80 While clinicians make dietary recommendations to individual patients, a liberal society is unlikely to accept dietary legislation beyond banning sweetened drinks in schools or mandating the content of food labels. Applying eco-social thinking, population health advocates would argue that such efforts will have limited success and attention should be directed upstream, towards the underlying determinants that give rise to groups of risk factors, rather than targeting specific factors and particular diseases.

Moving upstream: the health of populations

The ecological model of health introduced in Chapter 1 is often represented by concentric circles of determinants around the individual, as illustrated in Figure 2.7. Figure 2.9 applies the concentric circles metaphor to a causal analysis, and to points of intervention. The upper quadrants of the diagram portray the themes of understanding and analysis: the “Why?” and “How?” questions. Explanations for why a disease is prevalent typically seek answers in the outer circles in the diagram (shown in the north-west quadrant), whereas “How?” questions concern mechanisms and focus more specifically on the inner circles (NE side). Physicians like Dr. Rao direct their attention towards the inner circles: Peter Sulawesi and his immediate environment. By contrast, public health physicians act on broader determinants (e.g., collaborating with the housing authority to improve housing standards), and thus work on the intermediate circles. Meanwhile, government ministries of Health or the Environment will need to consider the broadest determinants operating at the outer circles of the diagram. Ideally, this combination of actions forms an orchestrated set of approaches to improve the health of individuals and of the population at large.

The arrows in the SW part of Figure 2.9 illustrate the idea that the influence of environmental determinants runs inwards from the outer circles: national policies influence communities; city policies affect neighbourhoods and thence individuals. But at the same time, the sigmas in the SE part suggests that actions of individuals combine to influence their environment, so that risk and protective factors from inner levels aggregate up to influence the outer levels. This is not a simple summation, however, for interactions occur, in the form of political and social movements, as suggested by the curved arrows in the southern part of the diagram. Individual risk factors derive from, but in turn influence cultural norms, cumulating to form group-level determinants. This distinction returns to the alternative views of population health – as an aggregate of individuals or as something greater than the sum of its parts.

Figure 2.9: An ecological model of the influences on health
Figure 2.9: An ecological model of the influences on health

The distinction between determinants and risk factors relates to a contrast drawn by Geoffrey Rose between the determinants of patterns of incidence and causes of individual cases.81, 82 Figure 2.10 links these distinctions to the population health versus clinical perspectives in analysing health. Analyses in the upper half of the figure represent the population health perspective; they focus on the causes of patterns of health and speak in terms of broad ecological pressures or determinants acting on whole groups of people. This predicts absolute risk, or the numbers of cases of disease: INCIDENCE rates. Analyses in the lower half of the diagram mirror a clinical perspective and speak in terms of individual risk factors and relative risk: which individuals are likely to fall sick and why? This perspective explains health in terms of individual characteristics.

Ultimately, both population and individual perspectives are necessary, the first for the public health specialist who operates on whole populations and the second for the clinician who tackles a patient’s risk factors to prevent disease.

Figure 2.10: Complementary perspectives in analysing the health of a population.
Figure 2.10: Complementary perspectives in analysing the health of a population.

Self-test Questions

1. What are the “social determinants of health”?

Aspects of the social structure, functioning, and institutions of a society that represent underlying causes of patterns of health, through numerous different channels. There are many lists of determinants; such as the Public Health Agency of Canada’s list of 12: Income and social status; Social support networks; Education and literacy; Employment/working conditions; Social environments; Physical environments; Personal health practices and coping skills; Healthy child development; Biology and genetic endowment; Health services; Gender; Culture.

2. Describe the channels through which social determinants affect the health of a population

Many academics have tackled this question (reviewed in reference # 22). How, in effect, do external forces “get inside the skin”?  Environmentally, you can cite differential exposures that relate to where a person lives and works, which reflect their socioeconomic position in society. Behaviorally, you may cite socially influenced patterns of lifestyle and health behaviours. Wealth, of course, plays a central role, creating differing levels of access to resources such as adequate nutrition, health literacy and health care that lead to differences in prevention & care when a problem does arise. Psychologically, different reactions to adversity generate feelings and emotions that may be damaging to health, or health enhancing (despair versus confidence; sense of control or self-efficacy, etc). Personal coping skills affect how deeply life stresses generate physiological strains, a process that may be mitigated by the person’s level of social connections that can supply practical assistance and reliable information, as well as emotional support.

3. What do we mean by health inequities?

Inequalities in health that place an identifiable group at a systematic disadvantage and that are (in theory, at least) preventable and correctable: things such as lack of access to health care for uninsured people; shorter life-span for poor people. Inequities offer a moral imperative for action.

4. Illustrate how gender can produce health inequities

Note that this question can equally apply to identifiable social groups besides gender.  For gender, one may begin by questioning social values: are women treated equally, allowed equal access to resources and opportunities, and genuinely respected as equals? Are there programmes in place to achieve genuine equality of opportunity (e.g., leadership programs for women)? While being respected as equals, are any differences between the sexes also respected, for example in terms of approaches to medical diagnosis and treatment?

5. What could you, as a physician, do about inequities in health?

Advocacy role: by advocating for effective, evidence-based preventive actions that can be applied universally and thereby reduce inequities. Physicians carry immense respect in society and can effectively lobby governments to draw attention to social issues. Drawing attention to the health consequences of inequities by citing specific and real-life examples forces the audience to consider the issue in personal terms: they, too, may be at risk of this disease; they are paying for expensive care for preventable conditions through their taxes, etc. Physicians can also outline effective actions to take to correct inequities: often these are very simple regulations such as banning unsafe toys; installing gates on stairs in homes with toddlers; advocating for child car seats.

6. At what stage of the life course would a public health practitioner seek to intervene to prevent the greatest amount of illness?

Most would argue that ensuring healthy early child development offers the best return on the dollar. See the work of Fraser Mustard.


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