Inequality and health
Inequality abounds in our world. We are born with genetic endowments that result in some of us becoming (or at least, having the potential to become) smarter, taller or stronger than others; our genetic inheritance can also mean we are more or less likely to experience depression, colon cancer or high blood pressure. However, inequalities also arise from our environments. For example, Australian research on twins shows that 22–48 per cent of differences in literacy are due to the influence of environmental factors related to home, school, friends, illnesses and the intrauterine environment.
Although nothing can be done about the inequality arising from our genetic inheritance, we have considerable ability to reduce it through altering our environment. Indeed, over the past century or so, Australia and many other countries have made great progress towards a fairer society by instituting social safety nets, better rights and conditions for workers, and universal education, among other innovations. Nevertheless, various forms of social inequality persist, and there is mounting evidence that inequality itself is damaging to health. In this article we examine some of the foundational evidence for this proposition and discuss its implications.
The Whitehall Study
The Whitehall Study – in fact consisting of two studies, Whitehall I and II – is one of the best-known and most important studies of inequality and health.
In Whitehall I, Michael Marmot and his colleagues examined mortality rates over 10 years among 17 530 male British civil servants aged 40–64 years. The investigators were particularly interested in mortality due to coronary heart disease (CHD). They administered a cardiovascular health questionnaire, asked questions about smoking, respiratory symptoms, medical treatment and physical activity, and recorded electrocardiograms, blood pressure, plasma cholesterol, blood glucose, skinfold thickness, height and weight.
Prior to the Whitehall Study, it had been a widely held assumption that people at higher levels of employment hierarchies had worse health and shorter lives than the people below them, due to more stress associated with greater responsibility and frequent decision-making. Similarly, conventional wisdom was that CHD was a disease of the affluent. However, the Whitehall investigators found the opposite: level of employment and mortality from CHD, as well as all-cause mortality, were inversely related. Men at the lowest level (e.g., messengers, doorkeepers) had three times the mortality rate of men in the highest level (administrators). Low employment status was associated with multiple risk factors – obesity, smoking, less leisure-time physical activity, more baseline illness, higher blood pressure, and shorter height – but even after controlling for these risk factors, workers in the lowest level still had a relative risk of 2.1 for CHD mortality compared to the highest.
The Whitehall investigators proposed that the explanation for the inverse relationship between employment status and CHD mortality was differences in job control and job support. Specifically, they hypothesised that characteristics of low-status jobs, such as underutilisation of skills, monotonous tasks and lack of clarity about objectives, were associated with job stress and therefore higher blood pressure, a major risk factor for CHD.
Whitehall I confirmed the significance of individual characteristics and their unequal distribution in society for health. To more thoroughly investigate occupational and other social influences on health and disease, Whitehall II, another longitudinal study of British civil servants, was established. It ultimately involved 6900 men and 3414 women aged 35–55 recruited from the London offices of 20 civil service departments.
Whitehall II showed that higher employment grade was associated with greater work control and variety (more freedom to make decisions) and faster pace (higher job demands). The difference in the prevalence of ischemia (inadequate blood supply to the heart) by level of employment was unchanged from Whitehall I. Subjects in lower-status jobs had worse self-perceived health status and symptoms. The investigators found significant employment level differences in risky health behaviours including smoking, diet, and exercise, in economic circumstances, in possible effects of early-life environment as reflected by height, social circumstances at work (e.g., low control, job dissatisfaction, few opportunities to learn), and social supports.
It is tempting to think that the marked differential in health between high and low-status workers detected in Whitehall I and II could be explained largely by income, and hence ability to acquire better healthcare, food, housing and other contributors to health. It is certainly true that a higher family income equates to a lower individual risk of dying and better health. It is also true that employment status correlates with income, and in the Whitehall studies higher proportions of participants lower down the hierarchy reported financial and housing problems and lived in rented accommodation (housing tenure predicts mortality, independent of occupationally defined social class).
However, none of the participants could be classed as poor, and as noted above, smoking, obesity, physical activity, blood pressure and other measures of health only partly explained the differences in mortality across employment levels. Moreover, even among people who are not poor, the higher the place in the hierarchy, the better the prospect of good health and long life. As Michael Marmot noted in 2004:
it is not the absolute amount of money that is important, but relative income. … [for example] Greece, with a national income of $17 000 (gross domestic product [per capita] adjusting for purchasing power), has longer life expectancy than the USA, with a national income of $34 000.
The association between height and employment status in the Whitehall I cohort is interesting, and is thought to partially reflect differences in early-life environment – including in the womb. In turn, height was inversely related to mortality; this is consistent with the burgeoning research that suggests the quality of the early-life environment (notably, the first 1000 days, which refers to the period between conception and the child’s second birthday) predicts disease in adult life. (Of course, it is also true that some of the health deficit associated with shortness in adulthood derives from the societal preference for height and consequent relatively high socioeconomic position of tall people.)
The social determinants of health
… the conditions in which people are born, grow, live, work and age. These circumstances are shaped by the distribution of money, power and resources at global, national and local levels. The social determinants of health are mostly responsible for health inequities – the unfair and avoidable differences in health status seen within and between countries.
The WHO identifies the social conditions in which people are born, live and work as the most important determinants of good or ill health. Similarly, Australia’s Health Performance Framework recognises the importance of social determinants to our health, including income, health literacy and educational attainment. Recognition of these determinants is a necessary step but must be followed with action to reduce their effects, as information recently compiled by the Australian Institute of Health and Welfare shows.
- In 2006, people reporting the worst mental and physical health (those in the bottom 20 per cent) were twice as likely to live in a poor-quality or overcrowded dwelling
- In 2009–10, people in low-economic resource households spent proportionally less on medical and health care than other households (3.0 per cent and 5.1 per cent of weekly equivalised expenditure, respectively)
- In 2009–2011, Australians living in the lowest socioeconomic areas lived about three years less on average than those living in the highest socioeconomic areas
- In 2013, mothers in the lowest socioeconomic areas were 30 per cent more likely to have a low birthweight baby than mothers in the highest socioeconomic areas
- In 2013, dependent children living in the lowest socioeconomic areas were 3.6 times as likely to be exposed to tobacco smoke inside the home as those living in the highest socioeconomic areas (7.2 per cent vs. 2.0 per cent)
Among the major recommendations deriving from the Whitehall studies were that ‘healthy behaviours should be encouraged across the whole of society, not just among the more privileged’ and that ‘attention should be paid to the social environment, job design, and the consequences of income inequality’. There has certainly been an increased focus on broad population health in the past few decades, from both researchers and policymakers, but considerably less on the second recommendation. Based on the evidence presented here, that must change if we are to achieve greater equity in health across society.
As Michael Marmot said in an address to the Royal College of Physicians in 2006:
The diseases of the slums of Nairobi are, to be sure, different in kind from the diseases that affect disadvantaged people in east London in the UK, or Harlem in the USA, and have different proximate causes. There is, however, a link. The unnecessary disease and suffering of disadvantaged people, whether in poor countries or rich, is a result of the way we organise our affairs in society. … failing to meet the fundamental human needs of autonomy, empowerment, and human freedom is a potent cause of ill health.