Over recent years, Dr. Blaser began to suspect that the organism, the dominant bacteria in the stomach, may play a role in human health as well as disease. This observation, he says, is consistent with a theory called the hygiene hypothesis. It suggests that exposure to microbial infections in early childhood prevents or diminishes the development of allergies and asthma.
Dr. Blaser has proposed that H. pylori may protect against diseases of the upper gastrointestinal tract, such as gastroesophageal reflux disease (GERD), which may lead to Barrett esophagus, a premalignant condition, and adenocarcinoma of the esophagus. All of these conditions have become more common in developed countries esophageal cancer of this type is the fastest rising cancer in the United States as H. pylori has become far less common due to improved sanitation and widespread use of antibiotics, says Dr. Blaser. (At the same time, the incidence of peptic ulcers and gastric cancer has declined in developed countries.)
Today, less than 10 percent of children carry the organism in industrialized countries, while some 90 percent of children are infected usually by age 5 in developing countries. "This bacterium has been the dominant organism in our stomach for tens of thousands of years, and it cant disappear from us without consequences," says Dr. Blaser. He says that a substantial body of work now shows that H. pylori helps protect against GERD and the conditions it leads to in the esophagus.
"The hypothesis that colonization of H. pylori, especially cagA strain, is protective of asthma risk needs to be tested by prospective studies. The findings from our study and others will collectively provide evidence," says Dr. Chen.
If the relationship between H. pylori and asthma is confirmed in other studies, which is always the yardstick of scientific validity, then it raises the question about whether "we sho
Contact: Jennifer Berman
New York University Medical Center and School of Medicine