The wheezing house

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Science Translational Medicine  02 Sep 2015:
Vol. 7, Issue 303, pp. 303ec149
DOI: 10.1126/scitranslmed.aad1827

Endotoxin inhalation has been linked to asthma and wheezing, but most studies investigating the link were performed either in children or a relatively small sample of adults. Now, Thorne et al. conduct a study in a large nationally representative sample of children and adults to determine the relationship between endotoxin exposure, asthma outcomes, and sensitization statuses for 15 allergens using the 2005–2006 National Health and Nutrition Examination Survey (NHANES) data.

The investigators hypothesized that the relation between house dust endotoxin and the prevalence of asthma and wheezing could differ with environmental exposures and sensitization to specific allergens. They found that higher endotoxin exposure was associated with wheezing and asthma during exercise in the 12 months prior to doctor or emergency room visits and use of prescription medications for wheezing. Predictors of high household endotoxin exposure identified in this study included poverty, age, pet keeping, cockroach infestation, indoor smoking, carpeting, and the age of the home.

This study is the first to assess the impact of endotoxin exposure on wheezing and asthma outcomes for a population that includes a significant number of adult participants. A previous study conducted by these same investigators from 1998 to 1999 that investigated the impact of endotoxins exposure using information from the National Survey of Lead and Allergens in Housing (NSLAH) found higher levels of endotoxin in the house dust from beds and bedroom floors compared with the levels noted in this study based on NHANES data. Although this difference might suggest that there has been a decrease in household endotoxin levels over time, the data more likely result from the fact that the NSLAH data was obtained using a smaller sample that was less representative of the U.S. population.

A limitation of this study is the fact that wheezing and asthma were documented on the basis of self-reporting from participants without verification. In addition, given the cross-sectional study design, the investigators cannot prove that endotoxin exposure and the respiratory outcomes observed are causally linked.

P. S. Thorne et al., Endotoxin exposure: Predictors and prevalence of associated asthma outcomes in the U.S. Am. J. Respir. Crit. Care Med. 10.1164/rccm.201502-0251OC (2015). [Abstract]

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