Previous studies suggest that an association exists between microbiological colonization and allergic disorders. The derived hygiene hypothesis postulates that the increase in atopic diseases may in part be due to diminished exposure to microorganisms. The study should contribute to clear up whether the association exist focused on chronic microbial colonization/infection and which type of infection does render the expected protection.
Methods:
As part of a 3 times repeated cross-sectional epidemiological study 4925 children in total have been medical checked up. Gastrointestinal and respiratory types of infection where considered: (1) gastrointestinal colonization (Helicobacter pylori detection using in vivo [13C] urea breath test) and (2) respiratory infections (physician-diagnosed lower (bronchitis) and upper (common cold) respiratory tract infections). Physician diagnosed allergic asthma, atopic eczema, rhinitis allergica and allergic symptoms were selected as allergic target variables.
Results:
Descriptive: Whereas respiratory infections lead to higher prevalence of the allergic disorders (not infected / infected: asthma 3/10 %, eczema 10/24 %, hay fever 6/12 %) Helicobacter pylori colonization protects against allergies (not infected / infected: asthma 6/3 %, eczema 16/7 %, hay fever 8/7 %).
Analytical: The descriptive results could be confirmed using a logistic regression adjusted for relevant confounders (gender, smoking and passive smoking, parental predisposition, pets (like cats), number of older siblings, duration of breastfeeding, socioeconomic status) except and not significant for rhinitis allergica. Related to asthma/eczema/hay fever the adjusted odds ratios (aOR) for Helicobacter pylori colonization were 0.58 (p=0.05) / 0.48 (p<0.01) / 1.07 (p=0.75). Contrary respiratory tract infection shows an amplifying effect on asthma / eczema / hay fever of aOR 3.75 (p<0.01) / 1.96 (p<0.01) / 2.07 (p<0.01).
Conclusions: Helicobacter pylori colonization seems to protect against allergic disorders in comparison with the effect of respiratory tract infections. The hygiene hypothesis may be better explained when this kind of gastrointestinal and respiratory tract infections are subtly differentiated.