The association between Chlamydia pneumoniae antibodies and wheezing in young children and the influence of sex

¹ University of Uppsala, Sweden
² University of Alberta, Canada
³ Karolinska Institute, Sweden

^* To whom correspondence should be addressed. E-mail: erik.normann{at}kbh.uu.se.

Accepted 12 July 2006

	Abstract

Background: The proposed association between Chlamydia pneumoniae (Cpn) infection and wheezing needs further clarification.

Methods: Sera from 1581 children in a population- based cohort were tested for antibodies to Cpn and IgE- antibodies to common allergens. Data on environmental factors and disease were collected prospectively from birth. Sera were obtained at the age of 4 years.

Results: Occurrence of IgG antibodies to Cpn at 4 years of age was associated with reported wheezing at different ages; however, these findings were most often not significant. In girls the occurrence of anti-Cpn-IgG was associated with wheezing at the ages of 1, 2 and 4 years, Odds ratio (OR)=3.41 [95% confidence interval (CI): 1.46-7.96], OR=2.13 [95% CI: 1.02-4.44], OR=2.01 [95% CI: 1.14-3.54], respectively, and even higher ORs were observed for each age category when only high level antibody responses to Cpn were analysed. At the time of blood sampling the association between anti-Cpn-IgG and wheezing was restricted to girls without atopic sensitisation, OR=2.39 [95% CI: 1.25-4.57]. No associations with wheezing were detected in boys, in whom IgE-sensitisation was inversely associated with the presence of anti-Cpn-IgG, OR=0.49 [95% CI: 0.26-0.90].

Conclusions: This study suggests an association between evidence of earlier Cpn infection and a history of wheezing in young girls. Infection with Cpn may be an important risk factor for wheezing and possibly for non-atopic asthma, predominantly in girls.

Keywords: Chlamydia pneumoniae, allergy, asthma, children, sex

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