Atypical bacterial pneumonia and asthma risk.

The role of respiratory infections in asthma is poorly understood. Atypical bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae are present in the lower airways of approximately 50% of asthmatics. This study tested the hypothesis that early life community-acquired pneumonia caused by Mycoplasma pneumoniae or Chlamydia pneumoniae is associated with increased asthma prevalence. Thirty-five subjects with a history of community-acquired pneumonia (22 due to atypical bacteria, 13 due to nonatypical pathogens) were evaluated by questionnaire 7-9 years after the episode of pneumonia. Subjects with a history of either typical or atypical pneumonia demonstrated increased asthma prevalence. Current or past asthma prevalence was 55% in subjects with atypical bacterial pneumonia and 61.5% in subjects with nonatypical bacterial pneumonia. Significant between-group differences were not demonstrated with regard to asthma prevalence (risk ratio=0.89; 95% confidence interval=0.49-1.61), current bronchodilator use [1.18 (0.44-3.17)], and family history of atopy [1.18 (0.73-1.91)], or asthma [1.63 (0.68-3.88)]. These data suggest that atypical bacterial pneumonia confers a risk of asthma similar to that seen with nonatypical bacterial pneumonia. Prospective studies are warranted to more fully evaluate the importance of atypical bacterial pneumonia as an asthma risk factor.