SAN DIEGO, Oct. 5 -- Eradication of Helicobacter pylori may have had the unintended consequence of unleashing an asthma threat even as the risk of gastric ulcer and cancer declined, results of a study reported here suggest.
H. pylori negativity predicted a significantly increased risk of early-onset asthma, asthma recurrence, and asthma severity in children, Martin J. Blaser, M.D., of New York University, said at the Infectious Diseases Society of America meeting.
H. pylori also had an inverse association with a history of wheezing, allergic rhinitis, eczema, dermatitis, and rash, he said.
"We started out just looking at asthma, but because we had data on all these other conditions, we decided to look at them as well," said Dr. Blaser. "What we found is that H. pylori had an inverse association with all of them, all of these essentially allergic disorders."
"The findings are consistent with the hypothesis that H. pylori protects against all of these conditions, and therefore, the disappearance of H. pylori is fueling, in part, the rise in these conditions. The data don't prove that, but they are consistent with the hypothesis."
Investigators explored the hypothesis using data from the 1999-2000 National Health and Nutrition Examination Survey, the most recent version of the survey to include test results for H. pylori. The NHANES database included information on 3,327 participants ages three to 19.
Comparison of H. pylori status and asthma history showed that participants who tested positive for the bacterium were 35% less likely to have any history of asthma (OR = 0.65; 95% CI = 0.43-1.01) and 44% less likely to have asthma onset before age five (OR = 0.56; 95% CI - 0.37-0.87).
Among participants ages three to 13, H. pylori seropositivity was associated with a 53% reduction in the relative risk of asthma (OR = 0.56; 95% CI = 00.37-0.87).
"Our findings are consistent with the hypothesis that H. pylori protects against asthma, possibly by priming the immune system in some way," said Dr. Blaser.
The reduced likelihood of wheezing, allergic rhinitis, eczema, dermatitis, and rash suggests H. pylori has a broader protective role that encompasses a variety of manifestations of atopia, he added.
The findings also support the hypothesis that H. pylori, as the dominant species when present in the stomach, affords natural protection against gastroesophageal reflux disease and, by extension, conditions associated with GERD. Dr. Blaser noted that GERD and asthma have a well-documented association.
The results also are consistent with findings that Dr. Blaser and colleagues reported earlier this year (Arch Intern Med 2007; 167:821-827). Also based on NHANES data, that study demonstrated a significant inverse association between H. pylori seropositivity and asthma history in adults, particularly childhood-onset asthma. (See: H. pylori May Offer Kids Asthma Protection).