Boston cross-sectional study

Endotoxin is part of the outer membrane of gram-negative bacteria, found ubiquitously in nature, being present in most indoor environments as a constituent of house dust. It has been suggested that endotoxin levels increase where animals are kept indoors and it seems noteworthy that two recent cross-sectional studies have shown a protective effect of early exposure to cats and dogs on the development of IgE sensitisation [146(111), 208(IIIC)]. However in a prospective birth cohort study in Boston a reduced risk of wheezing was shown in children whose mothers did not have asthma, but an increased risk in children whose mothers had asthma [209(IIIC)]. 

Table 13.5 summarizes results of six cross-sectional studies from U.S. locales, where the Pb exposure biomarker was bone Pb rather than PbB. Sample sizes varied as did the nature and extent of cardiovascular effect relationships to this more toxicokinetically stable biomarker. However, statistically significant associations of BP or hypertension with bone Pb were not consistently detected. Hu et al. (1996) analyzed for relationships of trabecular or tibial bone values with hypertension in mainly aging Boston, MA, Caucasian males enrolled in the VA NAS. No significant link of either bone Pb type with hypertension was identified. However, a second evaluation of male Boston enrollees in the NAS (/V = 519, cross-sectional analyses) using the same bone Pb biomarkers but SBP and DBP as continuous endpoint variables (Cheng et al., 2001) produced a positive significant association of tibial Pb and SBP but only an insignificant positive association of SBP with patellar Pb. 

Several pooled analysis and meta-analysis studies for multiple cross-sectional (meta-analysis) and prospective (pooled analysis) cohort evaluations have been published. Lanphear et al. (2005) reported on a pooled analysis of seven of eight longitudinal studies in the hterature that followed children until at least 5 years of age. Various criteria were employed for inclusion, such as complete analyses for covariates. The final sample size was more than 1,300 children drawn from the following cohorts Boston, MA Cincinnati, OH Cleveland, OH Rochester, NY Mexico City, Mexico Port Pirie, Australia and Kosovo, former Yugoslavia. Various forms of the exposure measure were included concurrent, maximum, hfetime average, and early childhood PbB. The psychometric outcome was full scale IQ. Within the combined data points for exposures, a subset of 103 children had maximum PbB < 7.5 jig/dl. 

U.S. Boston, MA, NAS (N — 459 men) PbB serially measured 1979-1994, 4-5 measurements, 10 ig/ dl = PbB mean, baseline Serum creatinine measured cross-sectional ly and prospectively Ln-transformed PbB was positively associated with concurrent serum creatinine In-transformed PbB positively linked to change in serum creatinine over follow-up in longitudinal study Kim et al. (1996)... 

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