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WASHINGTON (Reuters) - A bacterium that is a major cause of ulcers and stomach cancer may help protect children from developing asthma, U.S. researchers reported on Tuesday.
Children infected with Helicobacter pylori were much less likely to have asthma than uninfected children, they reported.
"Our findings suggest that absence of H. pylori may be one explanation for the increased risk of childhood asthma," said Yu Chen, assistant professor of epidemiology at New York University School of Medicine, who worked on the study.
"Among teens and children ages 3 to 19 years, carriers of H. pylori were 25 percent less likely to have asthma."
Children aged 3 to 13 were 59 percent less likely to have asthma if they also had H. pylori, they reported in the journal Clinical Infectious Diseases.
The researchers used data on more than 7,000 U.S. children from the National Health and Nutrition Survey conducted from 1999 to 2000 by the National Center for Health Statistics.
The study showed that 5.4 percent of children born in the 1990s tested positive for H. pylori.
"If you look at the people born in 1919, 60 percent are positive. That's a huge change," Blaser said in a telephone interview. "I have referred to this as global warming of the stomach."
During the same time, asthma rates have soared. Among the children aged 3 to 19 in the study, 23 percent had asthma, Blaser said.
"It's good and it's bad," Blaser said in a telephone interview.
"The disappearance of Helicobacter ... is consistent with the decline of both ulcer disease and stomach cancer. It is also consistent with the rise of asthma and esophageal diseases like GERD (gastric reflux disease) and adenocarcinoma (cancer) of the esophagus."
What needs to be studied, said Blaser, is whether Helicobacter infections directly affect a tendency to asthma.
"It is possible to H. pylori is a marker for something, just as blond hair is a marker for having been born in Scandinavia," he said
"Maybe the same antibiotics that made H. pylori go away make something else go away." Or perhaps the bacteria somehow protects against asthma directly, perhaps by changing the body's immune response.
"One explanation for this phenomenon has been termed the 'hygiene hypothesis,' which considers that humans are more prone to allergic disorders because of a lifestyle that may be too 'clean'," Blaser's team wrote.
The idea is the immune system doesn't have enough work to do early in life, so it becomes hyper-responsive to inappropriate triggers, such as dust, instead.
