British adults in their 30s and 40s are healthier than their counterparts in the US – but are more likely to think their health is poor, a study which includes the University of Oxford has suggested.

The health of the US “acts as a warning” of what Britain could be like without the “safety net” of the NHS, researchers said, with differences potentially down to access to healthcare, diet and levels of poverty.

For the study, academics from the UCL Centre for Longitudinal Studies, University of Oxford, Syracuse University and University of North Carolina used data from the 1970 British Cohort Study and the National Longitudinal Study of Adolescent to Adult Health.

Analysis included 9,665 British people born in 1970 and 5,381 US adults.

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It found adults in the US were more likely to have high cholesterol and high blood blood pressure, while four in 10 US adults were obese compared to 34.5 per cent of Brits.

However, 18 per cent of British adults were likely to report their health as poor compared to 12 per cent of adults in the US.

Britons were also more likely to smoke every day, with 28 per cent reporting cigarette use compared to 21 per cent in the US cohort.

Dr Charis Bridger Staatz, of the UCL Centre for Longitudinal Studies, said: “Our new research shows that although British adults are more likely to believe that their health is poor, they tend to have better cardiovascular health than their US counterparts in midlife.

“While we were unable to directly investigate the causes of this, we can speculate that differences in levels of exercise, diets and poverty, and limited access to free healthcare may be driving worse physical health in the USA.

“Given political and social similarities between the US and Britain, the US acts as a warning of what the state of health could be like in Britain without the safety net of the NHS and a strong welfare system.”

Professor George Ploubidis, of the UCL Centre for Longitudinal Studies, said the findings – published in the International Journal of Epidemiology – “should not distract” from levels of obesity and high blood pressure in Britain.

“In some ways, these findings could be seen to paint a positive picture for the nation, as the health of adults in Britain is better than that in the USA,” he said.

“Nevertheless, this research should not distract us from the fact that more than a third of British adults are obese and a fifth have high blood pressure in midlife.

“The new Government’s pledges to cut NHS waiting times will be severely tested if this and future generations continue to age in poor health.”