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Endotoxin exposure and childhood wheeze and asthma: a meta-analysis of observational studies. J Asthma 2011 Sep;48(7):685-93



Pubmed ID




Scopus ID

2-s2.0-80052019724 (requires institutional sign-in at Scopus site)   38 Citations


BACKGROUND: Exposure to endotoxin has been widely investigated as a potential factor for asthma and associated symptoms in children with different results. To clarify a potential relationship, we performed the present meta-analysis to integrate the results of studies examining the association of endotoxin exposure with wheeze and asthma in children.

METHODS: A search for relevant studies and reviews was conducted in MEDLINE, Highwire, CINAHL, and The Cochrane Library databases. Adjusted odds ratio (OR) with corresponding 95% confidence interval (CI) for endotoxin exposure and wheeze or asthma were retrieved and pooled to generate summary effect estimates in STATA 11.1.

RESULTS: Nineteen studies were included in the meta-analysis. The summary estimates suggested that endotoxin was positively associated with wheeze in infants and toddlers (meta-OR: 1.48, 95% CI: 1.10-1.98), but negatively related to asthma in school-aged children (meta-OR: 0.82, 95% CI: 0.69-0.97 for endotoxin concentration and 0.68, 95% CI: 0.50-0.93 for endotoxin load).

CONCLUSIONS: Based on the studies evaluated, endotoxin is a risk factor for wheeze in younger children, but a protective factor for asthma in older children. Thus, this study supports the "hygiene hypothesis."

Author List

Mendy A, Gasana J, Vieira ER, Forno E, Patel J, Kadam P, Ramirez G


Janvier Gasana MD, MPH, PhD Adjunct Associate Professor in the Institute for Health and Equity department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Environmental Exposure
Meta-Analysis as Topic
Respiratory Sounds
Risk Factors