According to a new study led by NYU Langone Medical Center researchers and involving more than 7,000 subjects, a bacteria that is known to live in the human stomach may protect children from developing asthma.

Although bacterium helicobacter pylori, which has co-existed with humans for at least 50,000 years, may also lead to peptic ulcers and stomach cancer, kids between 3 and 13 years carrying it are nearly 59 percent less likely to develop asthma.

The study appeared in the July 15 online issue of The Journal of Infectious Diseases and suggests that absence of H. pylori “may be one explanation for the increased risk of childhood asthma,” said Yu Chen, Ph.D., assistant professor of epidemiology at New York University School of Medicine and a co-author of the study.

“Among teens and children ages 3 to 19 years,” Chen added, “carriers of H. pylori were 25 percent less likely to have asthma.”

Dr. Chen collaborated on the survey with Martin J. Blaser, M.D., the Frederick H. King Professor of Internal Medicine, chair of the department of medicine, and professor of microbiology at NYU Langone Medical Center. Dr. Blaser has studied H. pylori for more than twenty years.

The results of the study are based on data gathered from 7,412 participants in the fourth National Health and Nutrition Survey (NHANES IV) conducted from 1999 to 2000 by the National Center for Health Statistics.

The study revealed that only 5.4 percent of children born in the 1990s carried the H. pylori bacterium.

"If you look at the people born in 1919, 60 percent are positive. That's a huge change," Blaser said in a telephone interview, as Reuters reports on its website. "I have referred to this as global warming of the stomach."

The rates of asthma have increased as the bacterium was less and less encountered in children. Twenty-three percent of the children aged 3 to 19 in the study had asthma.

H. pylori used to be almost universal in humans, the study says, but it has been disappearing from developed countries over the past century, probably due to increased antibiotic use, which destroys the bacteria, and also cleaner water and homes. There is a hypothesis which considers humans much more likely to develop allergic diseases because of a “too clean” lifestyle. As the immune system doesn’t have enough work to do early in life, it becomes hyper-responsive to inappropriate factors such as dust, instead.

The disappearance of the bacterium, Blaser says, is the cause for the decline of ulcer disease and stomach cancer, but, unfortunately, it is also the cause for the rise of asthma and diseases of the esophagus.

It has now remained to be studied 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.

Researchers also believe that the bacteria might somehow protect against asthma directly, perhaps by changing the body’s immune response. If children do not encounter Helicobacter early on, it is possible that their immune system does not learn to regulate a response to allergens.