HEALTH experts have long extolled the virtues of fresh country air - as opposed to the choking pollution of the big city - as one of the keys to a long and happy life.

But new evidence suggests those roles were reversed centuries ago, with city dwellers proving much hardier than their country cousins.

Researchers have compared human remains from Wharram Percy, a deserted medieval village near Malton, North Yorkshire, with bones unearthed from St Helen's Church, at Aldwark, once one of York's poorest parishes.

By studying tell-tale signs of disease on bone surfaces, investigators have discovered that while York inhabitants were more prone to infection, they were better able to combat diseases which proved fatal in the countryside.

The work has been led by Dr Simon Mays, human skeletal biologist with English Heritage, who believes the squalid and cramped conditions of medieval York exposed residents to a wider variety of ailments than rural areas, and that this helped build resistance for those surviving infancy.

Analysis has shown that diseases were far more likely to hit York residents, because of the insanitary conditions in the inner city.

But studies of periostitis - deposits of bone on lesions caused by disease and indicating long-term infection - have revealed intriguing features. Sixty-eight per cent of skeletons from York with periostitis showed remodelled bone, suggesting that people were rallying and, in many cases, overcoming illness. At Wharram Percy, the figure was just 40 per cent.

Dr Mays said: "It takes a long time for infectious disease to produce skeletal changes, so we are really looking at long-term conditions.

"Although bones from Wharram show fewer signs of infections, this may be because people succumbed to illness before these changes occurred. Once sickness arrived they had little natural resistance and quickly died.

"City dwellers may have been physically more robust, being exposed from birth to a large variety of pathogens. Together with evidence indicating stunted growth rates in children and relatively poor nutrition, rural life certainly wasn't romantic at Wharram Percy."

The findings are due to be published next year as part of a mammoth study of Wharram Percy, where extensive excavations were carried out between 1950 and 1990