Covariates in the ALHS analysis included age, sex, race/ ethnicity, smoking status (current/former/never), pack-years, asthma status, BMI, season, and state (IA vs.
Characteristics of the ALHS study population of 1,708 subjects (n = 645 asthma cases, n = 1,063 controls) that had endotoxin and peripheral blood cell count data are shown in Tables S7-S8.
Individuals in the ALHS study population (n = 1,646) were categorized as noncarriers (89%) if they were homozygous for both major alleles or as a variant carrier (11%) if one of the minor alleles was present, as described previously (Werner et al.
2003), in the ALHS, we found suggestive evidence that minor allele carriers at these loci do not exhibit an increase in WBC count with increasing endotoxin concentration.
Unlike the NHANES, in which significant endotoxin relationships to absolute counts of neutrophils, lymphocytes, and monocytes were observed, in the ALHS, endotoxin concentration was related only to neutrophil count, suggesting that the WBC relationship in the ALHS was largely driven by this cell type.
However, compared with other sampling sites for household endotoxin, bed dust, one of the primary sources of dust for our analysis in both NHANES and the ALHS, has been shown to have superior (reduced) within-home variance (Park et al.