Asthma sufferers who are also allergic to common airborne mold are 200 times more likely to stop breathing during an asthma attack than those who don't suffer from the allergy, according to a new study from the Mayo Clinic.

The study, published recently in the New England Journal of Medicine, reported that sensitivity to common mold spores found in grain fields during the fall and summer significantly increases the risk of breathing problems and can be fatal.

Researchers examined the cases of 11 asthma patients under 25 who suddenly stopped breathing during an asthma attack that occurred in the summer or fall. All the patients lived in the upper Midwest, where mold spores known as Alternaria alternata travel through the air from grain fields to urban areas. In two cases, the attacks were fatal.

Ten of the 11 asthma sufferers proved to be allergic to the spores, the researchers found, but fewer than 30 percent of a control group of asthmatics was allergic to the mold.

The findings suggest that "a small percentage of asthmatics may fall into this very high risk group," said Martin I. Sachs, associate professor of pediatrics at Mayo and a co-author of the study.

All asthma sufferers have sensitive airways, Sachs said. But in this group, exposure to the spores compounds the sensitivity and can lead to respiratory arrest, which may be fatal.

Previous studies have shown that about a quarter of all asthma attacks are triggered by exposure to some kind of allergen, Sachs said. But this is the first study that pinpoints specific mold spores as a culprit in respiratory arrest.

The key, he said, is to identify those for whom mold exposure is a problem and to treat them quickly with inhalants containing steroids or with ventilators.