New York -- Americans should be living four years longer at current rates of healthcare spending, signalling that US society is helping to make people sicker, a report on health inequality said on Thursday.

The report by the Robert Wood Johnson Foundation (RWJF), an influential US philanthropy, presented new evidence of widening disparities in health between income levels in the United States.

The nation's poorest adults were nearly five times more likely to be in "poor or fair" health as the richest - 31 per cent versus 6.6 per cent - and at every income level the wealthier group was healthier than the next lower one.

This trend of declining health according to income was seen in all race groups. Although socioeconomic factors are "harshest" on the poorest, the report said, "economic inequality has increased in the United States and the middle-class has lost ground."

Dr Risa Lavizzo-Mourey chief executive of RWJF said: "A far greater determinant is the sometimes toxic relationship between how we live our lives and the economic, social and physical environments that surround us. Some of the factors affecting our health we certainly can influence on our own; many of the factors, however, are outside our individual control."

The report and a new commission formed by the RWJF to look at remedies highlight potentially wider discussion and scrutiny on health disparities due to socioeconomic status and income inequality.

Researchers, including social epidemiologists, have long sought wider attention to socioeconomic forces to improve national health and reduce healthcare spending.

Dr Stephen Bezruchka, of the University of Washington school of public health, told the Financial Tines in an interview this month: "That is the key thing. Inequality basically shapes the whole structure of society. The thing is - in America - people seem to like it. But that's what's killing us."

US healthcare reform proposals have so far centred around better access to basic healthcare for all Americans, in particular 47m people without health insurance.

Americans' health and life expectancy is relatively poorer than other rich countries, even though the US spends more than $2,000bn a year on healthcare and nearly double per capita than the amount spent in the UK.

Dr Mark McClellan, former chief of both Medicare, the US health programme for elderly and poor, and the Food and Drug Administration said: "In fact, wealthy Americans have worse health than middle income Britons, as measured by several major chronic conditions. But there are promising strategies out there that show we can take practical steps to close the gap."

Dr McClellan will lead a commission comprised of leading private and public sector voices, including Wal-Mart, to explore how to mitigate US society's worsening health despite significantly higher healthcare spending than other countries.

It plans to take two years to formulate potential remedies to health disparities through in urban planning, economic development, improved schools and access to higher education, housing subsidies and health prevention efforts.

Linda Dillman, head of Wal-Mart risk management and benefits, said US society presents some obstacles to good health, and fixing them is good for the nation and makes better customers. "There are underlying causes that need to be addressed in this country. For instance, compared with Europe, we're a 'drive-thru' country," she said.