Middle-aged people in Britain are healthier than their American counterparts, despite healthcare costing nearly twice as much per person in the US, according to a study released yesterday.

The research found that rates of diseases such as diabetes, lung cancer and high blood pressure among Americans aged between 55 and 64 were up to twice as high as in England. Americans also had higher rates of heart disease, heart attacks and strokes.

The study's authors said lifestyle differences such as smoking, drinking and obesity could not explain the difference. They speculated that more fundamental differences may be to blame.

"It was surprising to find such a big gap between the two countries," said lead author James Banks, an economist at University College London. "If anything, given the higher health spending in the US, we might have thought that health levels would be a bit better there." Per capita spending on medical care is £1,176 in the UK compared with £2,866 in the US.

The disparities were all the more surprising because the team made the two sample groups as similar as possible. They used data from about 5,000 non-Hispanic white people aged between 55 and 64. Other studies have found that ethnic minorities suffer from different health problems for genetic and economic reasons.

The team found diabetes was twice as prevalent in the US (12.5%) compared with England (6.1%), and heart disease (15.1% compared with 9.6%), lung disease (8.1% compared with 6.3%) and cancer (9.5% compared with 5.5%) were all higher.

To check that the results were not a result of Americans reporting more health problems, the team also compared measurements of substances in the blood such as cholesterol. These also revealed large differences.

But the disparity was not simply down to lifestyle differences either. In both countries about one fifth of the study group were smokers, but heavy drinking was more common in the UK. Obesity was more common among the Americans, but not high enough to explain the difference.

Professor Banks speculated that experiences earlier in life might be responsible. Perhaps childhood obesity left a health imprint that shows up later in life. "The obesity epidemic began later here, we are now catching up," he said. "If that is the explanation then this health gap may potentially be closing in the future."

Obesity rates among under-10s in the UK have risen from 9.6% in 1997 to 13.7% in 2003 and the British Medical Association believes this will lead to more heart disease and some cancers.

Another of the study's findings was that moving up the economic ladder improved health. "A lot of the discussion is about poverty - poor people have poor health and everybody else has reasonable health. But that isn't what the data show," said co-author Sir Michael Marmot, of University College London. "The higher you are the better your health, the lower you are the worse your health."

He thought the reasons for this gradient could also explain the health gap.

Although the economic gap between people at the top of US society and those at the bottom was larger than in the UK, the health gap was about the same, so the difference must be due to more than just inequality.

"It might be that the nature of an unequal society is affecting everybody," he said.