Methods: To investigate potential relationships between household pet exposure, cord blood (CB) vitamin D and IgE concentrations and the number of upper respiratory infections (URIs) in the first year of life, we analyzed information from a geographically-based, prospective, non-high-risk, birth cohort. Household pets were assessed during pregnancy and medical records were abstracted for doctor visits of URIs. Because of large differences in vitamin D concentrations between Blacks and Whites racial stratification was done for some analyses.
Results: The cohort consisted of 1055 children of whom 62.4% were Black and 49.4% were female. When all children were considered, a one natural log unit increase in CB vitamin D concentration was associated with a greater risk of a URI visit (RR = 1.27, 95% CI 1.01-1.59, p=0.037) which remained after adjusting for the season of birth (RR = 1.28, p=0.033). Individually adjusting for the number of children in the family, CB IgE, child gender, family or maternal smoking and race did not substantially change the association of vitamin D to URIs (all RR’s were 1.25-1.27), although the risks only remained statistically significant with CB IgE (p=0.035) and gender (p=0.043). When models stratified by race including pets, dogs only, or cats only, and CB IgE were fitted with the other variables, the relationship between CB vitamin D disappeared for whites but did not change in magnitude for blacks (RR =1.31; 95% CI 0.89-1.92; p=0.165). Among Whites the only variable associated with URIs was a relationship with female gender (RR = 0.62, 95% CI 0.41-0.94; p=0.025) with being in daycare approaching significance (RR=1.72, 95% CI 0.94-3.14; p=0.08).
Conclusions: In a large, prospective, non-high-risk birth cohort higher, CB vitamin D concentration, after adjusting for other potential confounding variables, was not associated with a decreased risk of physician diagnosed URIs in the first year of life.