Asthma and allergic symptoms in relation to house dust endotoxin: Phase Two of the International Study on Asthma and Allergies in Childhood (ISAAC II)

Abstract

SummaryBackground Several studies have consistently reported inverse associations between exposure to endotoxin in house dust and atopy. With regard to the association between house dust endotoxin and asthma, the results are inconsistent. Objectives To study the association between house dust endotoxin levels and respiratory symptoms and atopy in populations from largely different countries. Methods Data were collected within the International Study on Asthma and Allergies in Childhood Phase Two, a multi-centre cross-sectional study of 840 children aged 9-12 years from six centres in the five countries of Albania, Italy, New Zealand, Sweden and the United Kingdom. Living room floor dust was collected and analysed for endotoxin. Health end-points and demographics were assessed by standardized questionnaires. Atopy was assessed by measurements of allergen-specific IgE against a panel of inhalant allergens. Associations between house dust endotoxin and health outcomes were analysed by logistic regression. Odds ratios (ORs) were presented for an overall interquartile range increase in exposure. Results Many associations between house dust endotoxin in living room floor dust and health outcomes varied between countries. Combined across countries, endotoxin levels were inversely associated with asthma ever [adjusted OR (95% confidence interval (CI)) 0.53 (0.29-0.96) for endotoxin levels per m 2 of living room floor] and current wheeze [adjusted OR (95% CI) 0.77 (0.64-0.93) for endotoxin levels per gram of living room floor dust]. There were inverse associations between endotoxin concentrations and atopy, which were statistically significant in unadjusted analyses, but not after adjustment for gender, parental allergies, cat and house dust mite allergens. No associations were found with dust quantity and between endotoxin exposure and hayfever. Conclusion These findings suggest an inverse association between endotoxin levels in living room floor dust and asthma in children.

Respiratory health and indoor air pollutants based on quantitative exposure assessments

“…Findings from epidemiological studies are less consistent [74]. Whereas some reports suggest a protective effect of endotoxins on the development of allergies [57,[75][76][77], others found that the exposure to endotoxins constitutes a risk factor for respiratory symptoms [78][79][80][81][82][83][84], which might depend on the amount of exposure [85].…”

“…However, several population-based studies have shown a decreased risk of wheezing [76], asthma [57,76] and atopy [76,88] in children living in urban homes with high endotoxin concentrations. Such a protective effect has been observed previously in rural populations, especially in the case of allergic sensitisation and atopic wheezing [75,89].…”

“…Such observations suggest that these compounds might have protective or adverse effects according to atopic status. Indeed, epidemiological studies have found positive [68,69,88] and negative [57,76] associations either in atopic or nonatopic asthma phenotypes. Moreover, timing of exposure seems to be crucial in order to understand how these components could be implicated in asthma.…”

Sick building syndrome: are we doing enough?

“…In damp buildings, mould and bacteria grow by enjoying the hospitable environment existing in settled dust (Lim et al 2015). Endotoxin (found in the outer cell membrane of gram-negative bacteria) (Gehring et al 2008) and (1,3)-β-glucan (found in the cell-walls of mould) (Iossifova et al 2007) are the two common compounds living in building dampness, causing proinflammatory effects (Lim et al 2015). Given these explanations, it can be inferred that the level of seriousness and the period of emerging symptoms once the occupants are exposed to sick environments can be highly variable.…”

Otitis, rhinitis, and atopy in relation to domestic endotoxin and β-glucan exposure among children in Singapore

“…Ever since Strachan published the theory on the hygiene hypothesis [1], it has become more and more apparent that exposure to microbial cell wall agents (MCWAs) plays an important role in the pathogenesis of these diseases. There are numerous studies that demonstrate an influence of bacterial endotoxin (lipopolysaccharide; LPS) on atopy, allergic skin disease, and asthma [2][3][4][5][6]. Endotoxin as such causes an inflammatory response in the airways and has been shown to increase the frequency of wheeze and airways irritation among children as well as adults.…”