COPD is often caused by smoking, but earlier work has shown a large intake of cured meats like hot dogs and ham is also linked to development of the lung disease.

While there is still no proof that such products actually cause COPD, the new research supports dietary recommendations to cut back on their consumption, said Judith Garcia-Aymerich of the Center for Research in Environmental Epidemiology in Barcelona, who led the new study.

Her group tracked 274 people up to more than three years after they were first hospitalized for COPD.

At the start, they surveyed people's eating habits, including how much cooked ham, Spanish cured ham, sausages and hot dogs they ate daily.

The researchers then divided the participants into two groups of the same size, according to whether they ate less or more than 23 grams of cured meats -- about one slice of ham or half a hot dog -- a day.

Of the 138 people in the low-consumption group, 30 percent were readmitted to the hospital during the study, compared to 40 percent in the group that ate higher levels of cured meats.

After taking into account differences between the groups, such as whether people smoked or took certain medications, the researchers found that those eating the most cured meat were twice as likely to go back into the hospital as those who ate the least.

"Doubling the risk is fairly substantial," said Dr. R. Graham Barr of Columbia University in New York, who was not involved in the new work but has done similar research. "So that tends to make us be more convinced that there may be a true signal."

While there is still no final answer on cause-and-effect, Garcia-Aymerich said the nitrites used as a preservative in the meats might be a potential culprit.

The authors write in their study, published in the European Respiratory Journal, that nitrites can produce molecules shown to harm the lungs of lab animals.

"It suggests there's a biological mechanism by which nitrites can damage the lungs," Barr told Reuters Health. "The question is whether any of that is relevant to people."

Garcia-Aymerich said it's also possible that the high levels of salt in cured meats might contribute to problems with COPD, "but we really don't know."

The U.S. Department of Agriculture recommends that people limit their consumption of processed meats. But Barr said the new study is not enough to urge people with COPD to steer completely clear of the products. SOURCE: European Respiratory Journal, online March 9, 2012.

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