Early Bacterial Infection May Boost Asthma Risk
Babies exposed to certain germs more likely to develop breathing problems, study finds
WEDNESDAY, Oct. 10, 2007 (HealthDay News) -- Babies who had certain bacterial infections in their first month of life were more likely to develop asthma by the time they were 5 years old, a new study found.
Danish researchers found that infants who tested positive for Streptococcus pneumoniae, Haemophilus influenzae or Moraxella catarrhalis bacteria had more than double the risk of asthma compared to infants who weren't infected. And they had four times the risk of being hospitalized for severe asthma when compared to infants who didn't test positive for these bacteria.
"Colonization of pathogenic bacteria in the newborn child is a strong predictor for the risk of asthma later in childhood," said the study's lead author, Dr. Hans Bisgaard, professor and head of the Danish Pediatric Asthma Center at Copenhagen University Hospital.
Results of the study are published in the Oct. 11 issue of the New England Journal of Medicine.
Despite the increasing prevalence of asthma, scientists still aren't sure exactly what causes the development of this potentially life-threatening airway disease. Genetics appear to be at least partly to blame, and environmental factors also likely play a role. Bacterial infections can trigger asthma symptoms in people who have the disease, but it hasn't been known if bacteria play a role in the initial development of asthma.
To assess the effects of bacteria in the development of asthma, Bisgaard and his colleagues obtained cultures from 321 babies when they were 1 month old. They tested the cultures for S. pneumonia, H. influenzae, M. catarrhalis and Staphylococcus aureus.
The researchers found that 21 percent of the babies were infected with S. pneumoniae, H. influenzae or M. catarrhalis. They also found that infection with these bacteria was associated with a 2.4 times increased risk of a persistent wheeze, a 2.99 times greater risk of acute severe exacerbation of wheeze, and a 3.85 times increased risk of hospitalization for wheeze. No such association was found with S. aureus infection, according to the study.
Once these children reached 5 years old, the prevalence of asthma was 33 percent for those who had earlier bacterial infections, compared to 10 percent for those who hadn't been infected.
"There are two possible interpretations: either this finding suggests that the initiating events of asthma and allergy are caused by bacterial colonization -- in analogy with the discovery that ulcer was caused by the Helicobacter pylori infection -- or this association between bacterial colonization in neonates and later development of asthma is [the result of underlying asthma and a deficient immune response to the bacteria]," Bisgaard said.
Dr. Erika von Mutius is a professor of pediatrics at University Children's Hospital in Munich, Germany, who wrote an accompanying editorial in the journal. She said it is hard to tell from this study "whether [bacteria] really are a causal factor or merely an indicator that the disease is developing."
In her editorial, von Mutius wrote, "In my opinion, the data presented by Bisgaard and colleagues may be interpreted to suggest that bacterial colonization of the [throat] in the first four weeks of life indicates a defective innate immune response very early in life, which promotes the development of asthma."
Whether bacterial infections in the first month of life are a cause of asthma or simply a sign of an already susceptible immune system, Bisgaard said early colonization with bacteria could be an early warning of a child who's at risk of developing asthma. He and his colleagues are planning to conduct a randomized, controlled trial to see if using probiotics (dietary supplements or foods containing beneficial bacteria normally found in the body) to prevent these bacterial infections could reduce the risk of asthma.
To learn more about the potential causes of asthma, visit the U.S. National Heart, Lung, and Blood Institute.