Inequality: Of wealth and health

The rising affluence of the 1 per cent may not only mean there is less for everyone else. What does inequality mean for your health?
THE richest 1 per cent of society has pulled away from the rest of the population at a quickened pace in the past few decades. This asymmetrical distribution of wealth is nothing new - humans have lived in lopsided societies for millennia. But the new question is whether their wealth affects everyone else's health. There may be economists who argue that inequality isn't bad for the health of the economy, but it is becoming more difficult to make the case that it doesn't harm the health of humanity. Growing evidence shows that greater inequality brings with it more crime, worse public health and social ills that affect every tier of society.
In recent decades, the proportion of wealth controlled by the top percentile has ballooned (see "Inequality: Who are the 1 per cent?"). But a global portrait shows that absolute poverty has actually dropped during that time. According to 2008 World Bank figures, 1.29 billion people live in absolute poverty, defined as getting by on less than $1.25 per day, down from 1.94 billion in 1981. The UN's millennium goal is to cut poverty by half from 1990 levels by 2015.
So increasing wealth at the top doesn't seem to drive more people into absolute poverty. However, once you move beyond destitution, another damaging problem is exposed: how you stack up against those around you in social and economic terms affects your health. Michael Marmot, an epidemiologist at University College London specialising in the health effects of inequality, sees the problem as one of relative poverty. Its ills are well documented and numerous: reduced access to nutritious food, healthcare and education and increased likelihood of exposure to violence have a significant impact on mental and physical health, as well as opportunities for socioeconomic advancement. "We shouldn't be thinking only of absolute destitution," he says.
Thomas McDade, a biological anthropologist at Northwestern University and director of Cells to Society at the Center on Social Disparities and Health at the Institute for Policy Research in Evanston, Illinois, says that additional research has unveiled a more challenging landscape. "Increasingly, we're coming to understand that even if you have a stable job and a middle-class income, then your health is not as good as that of someone who is in the 1 per cent. There is something more fundamental about social stratification that matters to health and the quality of social relationships."
The issues of relative poverty are more nuanced than meeting basic needs for food and shelter. A hundred years ago it might have been whether you could afford to eat meat once a week - or have an indoor toilet. Today it might be whether you can afford to mark your child's birthday with a party, Marmot says. "It matters because of what it means: can I participate in society?"

The great divide

Relative poverty goes hand in hand with inequality. "What we find is that the bigger the inequalities, income, educational, social, in a whole variety of ways, the bigger the health inequalities," Marmot says.
One of the measures used to assess economic disparities within a society is known as the Gini coefficient, which ranges from 0 - everyone earns the same - to 1 - one person takes it all (see graph). Most countries fall between 0.25 (Denmark) and 0.63 (South Africa). Studies have revealed the association between higher Gini scores and worse health outcomes, which include increased risk of premature birth and higher mortality rates.
meta-analysis conducted by S. V. Subramanian at the Harvard School of Public Health, and colleagues, showed that the US, with a Gini score of 0.36, had nearly 900,000 deaths that could have been avoided compared with nations with scores lower than 0.29. The UK, with a score of 0.33, had nearly 12,000 such avoidable deaths.
This analysis also revealed a threshold effect, in which detrimental effects on public health are only observed after inequality reaches a certain level. In this case, a Gini score of 0.3. "There's always going to be some degree of inequality," Subramanian says, but what matters is how drastic the degree is, or how quickly it shifts.
In the past two decades, more than three-quarters of the countries belonging to the Organisation for Economic Co-operation and Development have seen a growing gap between the rich and poor. "It's not just the idea of a threshold, but also how inequality has grown over time," Subramanian says. He and his colleagues stress that as inequality increases, more research on the link with poor health is urgently needed.
According to a 2011 report compiled by the US Congressional Budget Office, between 1979 and 2007, the average after-tax household income (adjusted for inflation) among the top 1 per cent of the US population grew by 275 per cent. Among the top fifth, it grew by 65 per cent; in the top two-thirds, by nearly 40 per cent; and in the bottom fifth, income grew by just 18 per cent.
The divergence in pay, with the top 1 per cent taking a larger share, amplifies inequality. Ultimately, says Marmot: "We're using the 1 per cent as shorthand for a bigger issue."
How does having less relative to your peers undermine health? Study after study identifies the culprit as stress. Not day-to-day fretting, but persistent psychological and physiological reactions to external threats that cannot necessarily be addressed or avoided. Much of this research focuses on those living in impoverished communities, but these associations only diminish by degree as you ascend the economic ranks of a society. "Socioeconomic status, and social stratification in particular, is a very powerful determinant of health - for populations and for individuals," says McDade.

Toxic stress

Unrelenting stress is toxic because it can turn the body's defence system against itself. Neuroendocrinologist Bruce McEwen at Rockefeller University in New York says the stress response that evolved to protect us from harm can be hijacked and actually cause harm when the stress never abates. In a normal situation, the introduction of stress causes the body to deliver a boost of energy - by sending a surge of glucose to the muscles - and to increase heart rate, blood pressure and breathing to get oxygen to the muscles in a hurry. At the same time, blood vessels constrict and clotting factors increase - ready to slow bleeding in case you are wounded. These responses are part of a fight-or-flight survival kit, and once the stress has passed, these should subside.
But for people under unremitting stress, this response never quite switches off - leaving sugar levels unregulated, high blood pressure, increased risk of blood clots, depressed sex drive and an immune system buckling under the strain. Prolonged exposure to stress hormones can have other effects as well, including affecting the brain by altering the structure of neurons and their connections, which in turn can influence behaviour and change hormonal processes.
In the well-known Whitehall II study, which followed more than 10,000 UK civil servants since 1985, Marmot and his colleagues found that reported stress levels were amplified as you descended the organisational hierarchy - with corresponding declines in health. Workers on the bottom of the heap were far more likely to suffer coronary heart disease than those at the top.
In a 2009 study, Michelle Schamberg and Gary Evans at Cornell University in New York looked at the role stress plays in the educational performance gap between those from richer and poorer backgrounds. The researchers hypothesised that childhood stress might impair working memory. They assessed 195 17-year-olds, about half of whom grew up below the poverty line and half in middle-income families.
To measure the amount of stress the children endured over the years, the researchers drew on a measure called allostatic load, with higher numbers indicating higher levels of exposure to stress. It is the sum of six risk factors: blood pressure (systolic and diastolic); concentrations of three stress-related hormones (cortisol, adrenalin and noradrenalin); and body mass index.
On average, the figures were higher for the poor children than for those from the middle-income families. A discrepancy in working memory broke down along the same lines. The 17-year-olds who lived in poverty could hold an average of 8.5 items in their memory at a time, compared with the better-off children, who could run to 9.4. When Evans and Schamberg ran statistical analyses to control for the effects of allostatic load, the relationship between upbringing and working memory disappeared; the deficits seen in the poorer children seemed to be down to their experience of stress.
The Centers for Disease Control and Prevention in Atlanta, Georgia, have also accumulated several decades' worth of data about stress and childhood. As part of ongoing studies into childhood risk factors, researchers came up with a stress scoring system. The method shows how, as the number of adverse experiences increases, so does the risk of health problems ranging from alcoholism and chronic obstructive pulmonary disease to heart disease and suicide attempts.
And in an intriguing 2007 study, Peter Gianaros at the University of Pittsburgh, Pennsylvania, examined the correlation between the way people classify themselves in terms of socioeconomic status, and the size of the perigenual area of their anterior cingulate cortex, a region of the brain involved in self-control, the experience of emotion and the regulation of reactions to stress. In an experiment with 100 men and women, Gianaros found that the lower the participants ranked themselves in terms of socioeconomic status, the smaller the volume of this area.
It is a preliminary finding, but McEwen speculates that awareness of one's own circumstances is likely to be a factor. "If you're living in a place like New York City with huge gradients of differences between rich and poor, you're going to know where you are. You're going to have the sense that 'I'm not able to do this or that'. It's going to have even more of an effect on how you view yourself and how you behave."
The uberwealthy, then, affect everyone else by extending the measuring stick by which we gauge our own successes and opportunities. But there are also other important ways in which they affect those below them.
"The magnitude of inequality damages social cohesion," says Marmot. "The rich live separate lives from the rest of us, live in different neighbourhoods, send their children to different schools." When the wealthy pay directly for the necessary services in their lives, they become less willing to spend tax money on everyone else, which begins to erode public services and creates a hierarchy of quality. "The whole argument against a service for the poor and a different one for the rich is that a service for the poor is a poor service," Marmot says. "That really says we are not one society."
Then there are health differences that change as you go up through society's ranks. A 2007 survey by the US Federal Reserve found that the wealthiest people were more likely to describe themselves as being in good or excellent health. This group also expected to live longer, while those with the least also had the lowest expectations for their longevity.
Health follows a social gradient, but Marmot argues that at some point, as wealth increases, the additional rise in health becomes very shallow. "The difference between somebody earning $1 million and $2 million is just not detectable in the evidence," he says. "You don't keep getting more and more benefit from more and more income." The extra millions piled on top aren't going to make the 1 per cent live much longer, but even a small amount of extra income could make a huge difference to the health of a swathe of the population below.
The policy implications seem obvious, if politically contentious: a more even distribution of wealth would improve health on national and global scales. But that appears unlikely to happen without a radical shift in western political culture; in recent times governments of all political persuasions have presided over growing inequality.
As the divide between the top percentile and everyone else widens, inequality is an issue that will not go away. And as the body of evidence accumulates, a clearer picture is emerging of inequality and its relation to health, self-worth, the ability to participate in society and to take control of one's life. Knowledge, as they say, is power - especially in the hands of 99 per cent of the population.
Liz Else is associate editor at New Scientist

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