Inequality and health: Lost in the mists of time?

When researchers try to understand whether rising inequality damages health, they often encounter puzzling results. At any given point in time, more unequal societies tend to have worse health, higher mortality, and a wider range of social problems. Yet when researchers look at changes in inequality over time – especially over short or medium periods – the expected effects often seem to vanish. This has led some to conclude that perhaps inequality does not matter.

But this conclusion reflects a misunderstanding of how inequality does its damage. If inequality acts primarily as a source of chronic social stress, then its effects will not appear as neat, time-locked changes in health or other outcomes. Instead, they spread unevenly and cumulatively through society and across the life course, more like a mist than a shock.

Stress resulting from inequality becomes embodied

Chronic stress does not work as an on-off switch. Persistent stress – arising from material deprivation, financial insecurity, social comparison, fear of falling behind, heightened class difference, or lack of control – becomes biologically embedded. Subjective social stress can have epigenetic effects, particularly when exposure occurs in early life. In adolescence, inequality can affect brain structure and function. And repeated activation of stress pathways alters the functioning of the cardiovascular, metabolic, immune, wound-healing, and nervous systems. Hormonal systems designed for short bursts of danger are pushed into long-term overdrive, with consequences that accumulate quietly over decades.

Persistent stress – arising from material deprivation, financial insecurity, social comparison, fear of falling behind, heightened class difference, or lack of control – becomes biologically embedded

Crucially, age at exposure matters. Stress experienced before birth can influence birthweight and early development, increasing susceptibility to heart disease, diabetes, and stroke many decades later. Stress in childhood can alter immune function, emotional regulation, educational performance, and lifelong health behaviours. Stress in adulthood accelerates wear and tear on the body – sometimes described as “allostatic load” – increasing vulnerability to cardiovascular disease, depression and anxiety, substance misuse, and earlier death. Stress in later life compounds existing illnesses and hastens decline.

This means that when inequality rises sharply, its health consequences do not arrive on schedule five or ten years later. Instead, they appear at different times, depending on age, prior exposure, resilience, and circumstance. And different conditions involve different pathways: deaths resulting from mental ill health, violence, or substance abuse operate through different processes from those affecting degenerative diseases. Aggregated national statistics jumble all this together.

Stressful societies and the slow erosion of social cohesion

Inequality affects individual biology partly through its effects on social relations. In more unequal societies, people become more acutely aware of where they stand. Status anxiety intensifies, trust erodes, and everyday interactions are more easily charged with fear of failure and others’ judgement. People withdraw, avoid social interaction, and invest greater effort in impression management. Social life atrophies.

The erosion of social cohesion has widespread consequences. Humans are deeply social creatures: belonging, mutual recognition, and shared purpose are fundamental psychological needs. When inequality weakens these bonds, it diminishes the everyday sources of meaning that make life worth living. Voluntary cooperation declines, civic participation weakens, and public spaces become neglected.

Humans are deeply social creatures… when inequality weakens these bonds, it diminishes the everyday sources of meaning that make life worth living

Inequality also affects the provision of collective goods. Highly unequal societies rarely sustain good public services – from education and transport to housing and healthcare. As the affluent opt out, political support for shared provision declines. These changes feed back into stress, insecurity, poorer health, and reduced life chances, particularly for those lower down the social ladder.

Taken together, these processes generate a deteriorating psychosocial environment – like a kind of social miasma that seeps into bodies, relationships, and institutions over time. It is precisely this diffuse, cumulative character that makes the effects of inequality so hard to identify in analyses tracking change over time.

Medical progress masked the damage caused by rising inequality

This helps explain an apparent paradox of recent history. From the late 1970s into the first decade – sometimes the second decade – of this century, inequality rose sharply across much of the rich world, especially in the United States and the United Kingdom. Yet during much of this period, life expectancy continued to rise steadily. If inequality is so damaging, why did mortality trends not worsen?

Part of the answer lies in the remarkable pace of medical progress. From the 1970s to around 2008, advances in medical science transformed survival prospects for many life-threatening conditions. Across high-income countries from the 1970s through the late 2000s, dramatic reductions in mortality – especially from cardiovascular disease – were a dominant driver of rising life expectancy. CVD mortality rates in many affluent nations fell by roughly 40–80% over the past 50 years, primarily due to advances in medical treatment, the widespread use of statins and antihypertensive drugs, improved surgical techniques, and faster treatment of heart attacks and strokes.

Driven by earlier detection, better treatments, improved post-diagnosis care, but above all by the decline in smoking, cancer survival also improved. Survival after accidents and injuries also improved markedly as a result of advances in trauma care, emergency response systems, and intensive care. Combined with safer roads and vehicles, deaths per mile were halved.

In other words:  medical, preventative and technological advances lifted average life expectancy even as social conditions deteriorated. With the exception of widening health inequalities, medical progress masked the damage caused by rising inequality.

As medical progress slowed, the damage surfaced

However, from around 2010 onward, the pace of life expectancy improvement slowed markedly across OECD countries, with cardiovascular mortality declines decelerating sharply or plateauing in countries such as the United States and the United Kingdom. The easier gains from medical and risk-factor advances had largely been realised by the late 2000s.

It was then that the long-term consequences of decades of heightened inequality became clear. Across many rich countries – including the United States, the United Kingdom, France, the Netherlands, Germany, Canada, Australia, Spain, and Portugal – rates of mortality improvement slowed to an extent not seen in the post-war period. The prevalence of obesity, diabetes, and other social and behavioural risk factors offset some earlier gains, supporting the view that subsequent trends reflected broader social and economic determinants.

Mortality rose in the USA as a result of the so-called “deaths of despair”  which have been shown to be related to income inequality. Deaths rose from drug overdoses, alcohol-related deaths, suicides and cardiovascular disease, while life expectancy actually fell for several consecutive years, well before the Covid-19 pandemic. In the UK, progress largely stalled, particularly in poorer areas, bringing to an end one of the longest uninterrupted improvements in population health in modern history.

The rise in inequality from the late 1970s onwards was followed not by an immediate mortality shock, but by a prolonged period during which rapid medical progress compensated for worsening social conditions

Seen in this light, the timing makes sense and helps reconcile the findings of cross-sectional and longitudinal studies. The rise in inequality from the late 1970s onwards was followed not by an immediate mortality shock, but by a prolonged period during which rapid medical progress compensated for worsening social conditions. Once that compensatory force weakened, the underlying damage became visible. The unprecedented rise in inequality was, as we might have expected, followed by an equally unprecedented slowdown in mortality improvement and widening of health inequalities.

Inequality as a fog that gradually seeps into every corner of social life

Inequality does not behave like a toxin that produces a sharp spike in mortality after a fixed incubation period. It behaves more like a fog that gradually seeps into every corner of social life, altering trajectories rather than triggering events. Expecting to see clear effects in brief changes over time in national mortality data is to misunderstand the nature of the process itself.

Inequality has left such a deep imprint on health and wellbeing not because it suddenly kills, but because it slowly reshapes how people live, relate, cope, and age – until the damage can no longer be hidden, even by the most impressive achievements of modern medicine.