Household endotoxin reduction in the Louisa Environmental Intervention Project for rural childhood asthma

Abstract

Endotoxin exacerbates asthma. We designed the Louisa Environmental Intervention Project (LEIP) and assessed its effectiveness in reducing household endotoxin and improving asthma symptoms in rural Iowa children. Asthmatic school children (N = 104 from 89 homes) of Louisa and Keokuk counties in Iowa (aged 5-14 years) were recruited and block-randomized to receive extensive (education + professional cleaning) or educational interventions. Environmental sampling collection and respiratory survey administration were done at baseline and during three follow-up visits. Mixed-model analyses were used to assess the effect of the intervention on endotoxin levels and asthma symptoms in the main analysis and of endotoxin reduction on asthma symptoms in exploratory analysis. In the extensive intervention group, dust endotoxin load was significantly reduced in post-intervention visits. The extensive compared with the educational intervention was associated with significantly decreased dust endotoxin load in farm homes and less frequent nighttime asthma symptoms. In exploratory analysis, dust endotoxin load reduction from baseline was associated with lower total asthma symptoms score (Odds ratio: 0.52, 95% confidence interval: 0.29-0.92). In conclusion, the LEIP intervention reduced household dust endotoxin and improved asthma symptoms. However, endotoxin reductions were not sustained post-intervention by residents.

Keywords: air sampling; asthma; endotoxin; house dust; intervention; reservoir dust.

Figure 1:

LEIP Study timeline of enrollment, intervention and environmental sampling

Figure 2:

Change in airborne inhalable endotoxin concentration in the overall sample (a), in participants living in non-farm areas (b), and in participants living in farm areas (c). Change in reservoir dust endotoxin load in the overall sample (d), in participants living in non-farm areas (e), and in participants living in farm areas (f). Changes in endotoxin calculated using least square means derived from generalized linear mixed-effects modeling adjusted for age and gender of participants, season of sampling, place sampled in the home, location of the house (farm or non-farm for overall, except in stratified analysis by this variable), family income, smoking in the house, presence of central air conditioning, presence of pets in the house, and main heat source. *P < 0.05 **P < 0.01 ***P < 0.001