Britain and America are in the midst of a barely reported public health crisis. They are experiencing not merely a slowdown in life expectancy, which in many other rich countries is continuing to lengthen, but the start of an alarming increase in death rates across all our populations, men and women alike. We are needlessly allowing our people to die early.

In Britain, life expectancy, which increased steadily for a century, slowed dramatically between 2010 and 2016. The rate of increase dropped by 90% for women and 76% for men, to 82.8 years and 79.1 years respectively. Now, death rates among older people have so much increased over the last two years – with expectations that this will continue – that two major insurance companies, Aviva and Legal and General, are releasing hundreds of millions of pounds they had been holding as reserves to pay annuities to pay to shareholders instead. Society, once again, affecting the citadels of high finance.

Trends in the US are more serious and foretell what is likely to happen in Britain without an urgent change in course. Death rates of people in midlife (between 25 and 64) are increasing across the racial and ethnic divide. It has long been known that the mortality rates of midlife American black and Hispanic people have been worse than the non-Hispanic white population, but last week the British Medical Journal published an important study re-examining the trends for all racial groups between 1999 and 2016 .

The malaises that have plagued the black population are extending to the non-Hispanic, midlife white population. As the report states: “All cause mortality increased… among non-Hispanic whites.” Why? “Drug overdoses were the leading cause of increased mortality in midlife, but mortality also increased for alcohol-related conditions, suicides and organ diseases involving multiple body systems” (notably liver, heart diseases and cancers).

US doctors coined a phrase for this condition: “shit-life syndrome”. Poor working-age Americans of all races are locked in a cycle of poverty and neglect, amid wider affluence. They are ill educated and ill trained. The jobs available are drudge work paying the minimum wage, with minimal or no job security. They are trapped in poor neighbourhoods where the prospect of owning a home is a distant dream. There is little social housing, scant income support and contingent access to healthcare. Finding meaning in life is close to impossible; the struggle to survive commands all intellectual and emotional resources. Yet turn on the TV or visit a middle-class shopping mall and a very different and unattainable world presents itself. Knowing that you are valueless, you resort to drugs, antidepressants and booze. You eat junk food and watch your ill-treated body balloon. It is not just poverty, but growing relative poverty in an era of rising inequality, with all its psychological side-effects, that is the killer.

Shit-life syndrome captures the truth that the bald medical statistics have economic and social roots. Patients so depressed they are prescribed or seek opioids – or resort to alcohol – are suffering not so much from their demons but from the circumstances of their lives. They have a lot to be depressed about. They, and tens of millions like them teetering on the edge of the same condition, constitute Donald Trump’s electoral base, easily tempted by rhetoric that pins the blame on dark foreigners, while castigating countries such as Finland or Denmark, where the trends are so much better, as communist. In Britain, they were heavily represented among the swing voters who delivered Brexit.

Shit-life syndrome is not just a feature of a US city such as Baltimore, where the difference in life expectancy between the richer and poorer districts is as much as 20 years, it’s a feature of our cities, too. Within the London borough of Kensington and Chelsea, the difference in life expectancy between richest and poorest is 16 years. And the trends are deteriorating. Public Health England has published a hair-raising map of the English health experience from 2014 to 2016. The East and West Midlands, Yorkshire and Humberside, the north-west and north-east experienced declines in life expectancy. Nobody should have been surprised they voted against the status quo in the Brexit referendum.

What our citizens are experiencing is criminal, even if it has nothing to do with the EU, the great lie so brilliantly told by Brexiters and the malevolent political genius that is Nigel Farage. Instead of blaming Brussels and impoverishing ourselves with Brexit, Britain should be launching a multipronged assault on shit-life syndrome and the conditions that cause so many to die prematurely. Acknowledging the crisis, together with measures to address it, will be crucial to winning any second people’s vote on Brexit.

We need (as Andrew Adonis and I argue in Saving Britain) an industrial policy not just for the City, but for the country, a repurposing of enterprise, a re-enfranchisement of workforces and a remaking of our threadbare social contract, in particular the dysfunctional care system. Too many of England’s towns, even some in the south-east, are becoming crucibles of shit-life syndrome. They have become inward-looking, urban islands in which despair and despondency are too prevalent; their high streets in decline while hi-tech, knowledge-intensive jobs pass them by. Train and bus fares are so high that travelling within them has become prohibitively expensive. Stripped of power by the most centralised system in Europe, they are disempowered and sullen about the present and apprehensive of the future. All this can and must change.

Above all, it is an agenda for an effective parliamentary opposition – combining a campaign to stay in the EU with a campaign to change Britain. The life expectancy numbers tell a dramatic story. It is time to act on their message.

• Will Hutton is an Observer columnist