Regularly eating cured meat, including sausages and bacon, can almost double the chance of developing a chronic lung disease, according to new research.

Scientists believe such Scottish breakfast staples may harm the lungs in the same way as the serious chest condition emphysema.

Support groups yesterday called for further research to investigate the link, following the research.

Chronic obstructive pulmonary disease (COPD) is one of the most common lung conditions in the developed world, affecting one in 65 Scots.

It incorporates both bronchitis and emphysema and is among the most frequent causes of death for men from middle age onwards.

The disease is strongly associated with smoking, but up to one in 10 sufferers are non-smokers. The link with cured meat, which also includes salami and ham, may help explain why they succumb.

Scotland is known for its poor diet as well as high smoking rates and has the highest levels of respiratory illness in the UK.

The eating habits of 7352 individuals with an average age of 64.5 were studied by the US researchers investigating diet and COPD.

All those involved participated in the Third National Health and Nutrition Examination Survey, a major US health investigation conducted between 1988 and 1994.

Those who ate cured meat products 14 times or more a month were almost twice as likely to develop COPD as people who consumed none, the researchers found. They also performed more poorly in lung function tests.

Rui Jiang, the head of the study from Columbia University Medical Centre in New York, said: "Cured meats, such as bacon, sausage, luncheon meats and cured hams, are high in nitrites, which are added to meat products as a preservative, an anti-microbial agent and a colour fixative.

"Nitrites . . . may cause damage to the lungs, producing structural changes resembling emphysema."

The findings were published yesterday in the American Journal of Respiratory and Critical Care Medicine.

A spokesperson from Chest, Heart & Stroke Scotland said: "This study which shows an association between frequent consumption of cured meats and increased rates of COPD is very interesting but more research will be needed to find out if there is a direct causal link between them."