Introduction

This chapter describes biological and environmental determinants of the health of Australians, providing a background to the development of successful public health activity. You will recall from the Introduction to Section Two that health determinants are the biomedical, genetic, behavioural, socioeconomic and environmental factors that impact on health and wellbeing. These determinants can be influenced by interventions and by resources and systems (AIHW 2006). Many factors combine to affect the health of individuals and communities. People’s circumstances and the environment determine whether the population is healthy or not. Factors such as where people live, the state of their environment, genetics, their education level and income, and their relationships with friends and family are all likely to impact on their health. The determinants of population health reflect the context of people’s lives; however, people are very unlikely to be able to control many of these determinants (WHO 2007).

This chapter and Chapter 6 illustrate how various determinants can relate to and influence other determinants, as well as health and wellbeing. We believe it is particularly important to provide an understanding of determinants and their relationship to health and illness in order to provide a structure in which a broader conceptualisation of health can be placed. Determinants of health do not exist in isolation from one another. More frequently, they work together in a complex system. What is clear to anyone who works in public health is that many factors impact on the health and wellbeing of people. For example, in the next chapter we discuss factors such as living and working conditions, social support, ethnicity and class, income, housing, work stress and the impact of education on the length and quality of people’s lives.

Tackling health determinants has great potential to reduce the burden of disease and promote the health of the general population. In summary, we understand very clearly now that health is determined by the complex interactions between individual characteristics, social and economic factors and physical environments; the entire range of factors that impact on health must be addressed if we are to make significant gains in population health, and focusing interventions on the health of the population or significant subpopulations can achieve important health gains.

In Chapter 3 you were introduced to National Health Priority Areas including: cancer control, injury prevention and control, cardiovascular health, diabetes mellitus, mental health, asthma, arthritis and musculoskeletal conditions. As you will recall from that chapter, the National Health Priority Areas set the agenda for the Commonwealth, states and territories, local governments and not-for-profit organisations to place attention on those areas considered to be the major foci for action. Many of these health issues are discussed in this chapter and the following chapter.

A complex web of determinants

Determinants are in complex interplay and range from the ‘upstream’ background influences (e.g. culture and wealth), with many health and non-health effects that can be difficult to quantify, to immediate or direct influences with highly specific effects on particular aspects of health. They are often described as part of broad causal ‘pathways’ or ‘chains’ that affect health (Keleher & Murphy 2004).

The Public Health Agency of Canada (2007) defines 11 determinants of health (Table 5.1). Examining these issues briefly in tabular form gives you an idea of the range of factors that impact on health. Figure 5.1 collapses these many determinants into a manageable and simple framework for your consideration. Some of these determinants are discussed further in this chapter and the remaining determinants are considered in the following chapter.

TABLE 5.1 Determinants of health

Determinants of health	Description
Income and social status	Much research suggests poor people are less healthy than rich people; income distribution is a key element
Social support networks	Support from family, friends and community is linked to health
Employment and working conditions	Unemployment and poor health are related; more control over working conditions improves health
Education	Low literacy levels are linked to poor health
Physical environments	Clean air and water, healthy workplaces, safe houses, communities and roads all contribute to health
Genetics	Inherited characteristics play a role in determining how long we live, how healthy we will be and the likelihood of contracting certain illnesses
Personal health practices and coping skills	Physical activity, good nutrition, smoking and drinking and coping skills impact on health
Healthy child development	Good health in childhood has a positive influence on later life
Health services	Access to services that prevent diseases benefits health
Gender	Different kinds of diseases and conditions affect women and men differently
Culture	Customs and beliefs affect health

(Source: Public Health Agency of Canada 2007)

Fig. 5.1 Determinants of health.

(Adapted from AIHW 2004, figure 3.1)

Figure 5.1 presents a range of determinants and their pathways. The pathways are not linear and can also occur in reverse. For example, an individual’s health can influence their physical activity levels, employment status and wealth. General background factors and environmental factors can determine the nature of socioeconomic characteristics and both can influence people’s health behaviour, their psychological state and factors relating to their safety. These, in turn, can influence biomedical factors, such as blood pressure and body weight, which may have health effects through various further pathways. At all stages along the path these various factors interact with an individual’s genetic composition. This framework then shows us a simple way of organising and examining the various pathways that may occur in a range of different contexts.

An important use of determinants is to enable us to focus on where best to intervene. Turrell et al. (2006) identify three broad levels of factors affecting health and how interventions might be structured based on these levels, as follows:

• downstream factors include treatment systems, disease management and investment in clinical research

• midstream factors include lifestyle, behavioural and individual prevention programmes

• upstream factors involve government policies and investment in population health research as examples (Keleher & Murphy 2004).

One of the important uses for this type of approach is to ensure that we direct our resources upstream to focus on issues that impact on health equity. This issue will be considered in more detail in the next chapter.

Genetics and screening

Genetic determinants are important factors impacting on individual health and they will continue to be important, as nearly every disease has constitutive and/or acquired genetic components. Identifying disease susceptibility genes, as well as identifying acquired somatic mutations underlying a specific disease such as cancer, can provide vital information for a more thorough understanding of many common illnesses. This information can then be used to determine how diseases are diagnosed and how new treatments or particular drug therapies can be identified (Europa 2007).

‘Genes are the units of heredity which control the structure and function of the body by determining the structure of peptide chains that form the building blocks of enzymes and other proteins’ (Harper et al. 1994 p 119). A gene’s role is to ensure that the amino acids are always in the same order. Genes are located at specific points in the deoxyribonucleic acid (DNA) in the cell nucleus and the DNA is arranged into 23 pairs of chromosomes. Of these, 22 are called autosomes while the other pair is the sex chromosomes. One of each pair of chromosomes is derived from each parent. There are several categories of genetic disease depending upon the location and the extent of the genetic abnormality. The categories include single-gene disorders, chromosomal disorders, disorders involving several genes and environmental influences, disorders of cytoplasmic DNA and mutations of somatic cells.

In the case of single-gene disorders, they may be autosomal dominant, for example, Huntington’s disease and otosclerosis; autosomal recessive, for example, cystic fibrosis; or x-linked dominant or recessive, resulting in disorders such as muscular dystrophy and haemophilia.

Chromosomal abnormalities often cause fetal death and congenital disease. For example, about half of spontaneous abortions are linked to chromosomal abnormalities. Down’s syndrome is an example of a chromosomal abnormality.

The complex interplay of genetic and environmental factors is associated with the relationship between several genes at different loci on the chromosome, each with an additive effect and a variable environmental component. Characteristics determined in this multifactorial manner may be continuous or discontinuous. For a continuous multifactorial trait, such as blood pressure, there is a high continuous gradient from high blood pressure to normal blood pressure. An example of a discontinuous multifactorial variable is cleft lip and palate.

There is strong evidence of a genetic component to many conditions causing chronic illness and premature death. We must also keep in mind that the majority of diseases are multifactorial in aetiology and result from the interaction of multiple genetic and environmental factors.

Examples of the integration of genetics into public health functions in the twenty-first century include such activities as investigating clusters of cancer in communities, developing policies for using genetic testing to prevent iron overload in the USA, population analysis of the impact of asthma interventions based on individual susceptibility, evaluating the prevention effectiveness of a national campaign for early detection of colon cancer, and a national assurance programme to monitor the utilisation, effectiveness and impact of genetic testing. The implications for public health include treatment for affected high-risk individuals, prevention for at-risk individuals, health promotion activities among the general population and with regard to the environment, crop modification, pharmaceuticals and the cloning of animals, as examples.

However, genetic screening raises ethical, social and legal concerns relating to the privacy and confidentiality of genetic information, fairness in the use of genetic information, the psychological impact, stigmatisation and discrimination associated with the use of such information, reproductive and clinical issues and uncertainties associated with gene tests for susceptibilities and complex conditions. It will be interesting to follow modern genetics as it develops because it will undoubtedly have implications for the population’s health.

The Human Genome Project commenced in 1990 as a 15-year, large-scale, international project that involved the USA, the UK, France, Canada, Germany, Japan and China. The primary goal was to sequence the entire human genome, with other goals including identifying genes, improvements in technology and data analysis, comparative genomics and the ethical, legal and social implications of such a project. ‘From a public health perspective, there is a danger that the enthusiasm for genomics may deflect attention and resources from the important mission of preventing disease in the population’ (Schneider 2006 p 211). Genomics is the study of how genes act in the body, and how they interact with environmental influences to cause disease. The fundamental question for public health is the extent to which applying this emerging knowledge will divert resources from the mission of public health, which is to prevent disease in the population.

Diabetes is a good example of the complex interplay of genetic and environmental factors. Consider the following activity on diabetes as an introduction to the nature and impact of a chronic disease on health and wellbeing and the potential role of public health. If you are not familiar with diabetes, consider looking at the website located at the end of this chapter to become more familiar with the different characteristics of diabetes, for example, type 1 and type 2 diabetes, their development and prevention and treatment options. Then attempt the activity.

Reflection

Diabetes mellitus is a condition where the body cannot maintain normal blood glucose levels. There are three types of diabetes: type 1 diabetes, type 2 diabetes and gestational diabetes. A further category of diabetes is not common and accounts for less than 1% of people with diabetes. It includes diabetes caused by a variety of distinct genetic and pathological mechanisms that are generally clearly defined.

Diabetes is caused by resistance to, or deficient production of, the hormone insulin, which helps glucose move from the blood into the cells. When the body does not produce or use enough insulin, the cells cannot use glucose and the blood glucose level rises. This means that the body will instead start to break down its own fat and muscle for energy. Diabetes may lead to severe problems, including damage to the heart, blood vessels, eyes, nerves and kidneys (Department of Health and Ageing 2006 website). Diabetes is defined as a chronic disease in Australia. In the United States the definition of a chronic disease is different from the Australian definition. There are some websites listed at the end of the chapter that will help you consider different definitions of chronic disease. The last section of the activity asks you how public health might contribute to promotion, prevention and rehabilitation of people with diabetes. Think back to what you have learned about the nature of public health, the determinants that contribute to diabetes and what public health strategies might be put in place as prevention and rehabilitation strategies for diabetes.

Biological and behavioural determinants

Biological determinants

Biology refers to the individual’s genetic make-up, family history and the physical and mental health problems acquired during life. Ageing, diet, physical activity, smoking, stress, alcohol or illicit drug use, injury or violence, or an infectious or toxic agent may result in illness or disability and can produce a ‘new biology’ for the individual (Australian Institute of Health and Welfare 2010; Office of Disease Prevention 2007).

Behavioural determinants

Lifestyle or behavioural determinants are multidimensional and they are linked to a number of major health problems. Some health issues share the same determinants, such as tobacco, alcohol and nutrition.

Individual health practices are responses or reactions to internal stimuli and external conditions. Both behaviour and biology can have a reciprocal relationship, with each reacting to the other when a person is exposed to a particular health condition. Examples of the reciprocity of the relationship can be seen in the case of a family history of heart disease (biology), which may motivate an individual to add healthy eating behaviours, maintain an active lifestyle and avoid tobacco smoking (behaviours), thus preventing the development of heart disease (biology). Personal choices and the social and physical environments surrounding individuals can shape behaviours. The social and physical environments also include factors that affect the life of individuals, positively or negatively, many of which may not be under their immediate or direct control (AIHW 2010; Office of Disease Prevention 2007).

Reflection

Did you consider any of the significant factors discussed below? What factors may change if an individual could control the determinants of their health? Would it make it easier for them? Would it be more difficult? Does the environment play a role in the health issue you have selected?

Tobacco

Tobacco is clearly responsible for, in part, a worldwide epidemic of coronary heart disease and lung cancer. The work of researchers such as Doll and Hill (1964) clearly linked the smoking patterns of individuals with age and cause of death (Keleher & Murphy 2004). The World Health Organization (WHO) Global Burden of Disease Study (Murray & Lopez 1996) reported that, by 2020, it was expected that tobacco would account for 12.3% of deaths worldwide. Smoking rates have been declining for several decades in Australia. Between 1985 and 2007, the prevalence of smoking declined for both males and females. Despite these trends, tobacco smoking continues to cause more ill health and death than other well-known health determinants such as high blood pressure, overweight/obesity and physical inactivity (AIHW 2010). The impact of passive smoking, particularly on children, has become very important in recent years – increasing the likelihood of a number of illnesses, including chest and ear infections, asthma and sudden infant death syndrome (AIHW 2010).

Alcohol

Alcohol plays an important role in the Australian economy and it also has an important social role. It is a familiar part of traditions and customs in this country and is often used for relaxation, socialisation and celebration. Eighty-three per cent of Australians reported drinking alcohol in 2004. It is a drug that can promote relaxation and feelings of euphoria. It can also lead to intoxication and dependence and a wide range of associated harms (Ministerial Council on Drug Strategy 2006).

Although the per capita consumption of alcohol in Australia has declined since the 1980s it remains high by world standards. Many of the dangers of alcohol for those who drink, and those around them, are misunderstood, tolerated or ignored. The harms associated with unsafe alcohol use, including drinking to intoxication, are now well documented in the research literature. The National Alcohol Strategy 2006–2009 (the strategy) is a plan for action developed through collaboration between Australian governments, non-government and industry partners and the broader community. It outlines priority areas for coordinated action to develop drinking cultures that will reduce alcohol-related harm in Australia.

Some research suggests that benefits from alcohol consumption only occur at very low levels of drinking or that there is no protective effect from drinking (NHMRC 2009).

Injuries

Injury affects Australians of all ages and is the greatest cause of death in the first half of life. It leaves many with serious disability or long-term conditions. Injury is estimated to account for 6.5% of the burden of disease in 2010 (AIHW 2010). For these reasons, injury prevention and control was declared a NHPA and is the subject of three national prevention plans: the National Injury Prevention and Safety Promotion Plan: 2004–2014 (NPHP 2005a), National Falls Prevention for Older People Plan: 2004 Onwards (NPHP 2004) and the National Aboriginal and Torres Strait Islander Safety Promotion Strategy (AIHW 2010, NPHP 2005b). Injuries were responsible for almost half of the mortality for people under 45 years of age, and account for a range of physical, cognitive and psychological disabilities that seriously affect the quality of life of injured people and their families. Health costs associated with injury in Australia have been estimated to be $2.6 billion annually (AIHW 2010).

Injury usually means physical harm to a person’s body and the most common types of physical injury are broken bones, cuts, poisoning and burns. Physical injury results from harmful contact between people and objects, substances or other things in their surroundings, for example, being struck by a car, cut by a knife, bitten by a dog or poisoned by inhaled petrol. Some physical injuries are the intended result of acts by people: harm of one person by another (e.g. assault, homicide) or self-harm (AIHW 2010, NPHP 2004).

Over recent years, Australia has achieved some significant gains in preventing a number of different types of injuries where concerted efforts have been made. There have been improvements in road safety over the past 25 years. The reduction in road deaths has occurred despite significant growth in the population, vehicle numbers and kilometres travelled. Initiatives, such as random breath testing, compulsory seat belts, speed blitzes, car design and safety features (e.g. air bags), better roads, ongoing community education regarding road safety and improved life-saving medical procedures and trauma care, have all contributed to the decline in the number of vehicle-related fatalities (AIHW 2010, NPHP 2004).