Tobacco smoke exposure and allergic sensitization in children: a propensity score analysis.

BACKGROUND AND OBJECTIVE: There is conflicting evidence of the effect of environmental tobacco smoke (ETS) on the development of allergic diseases in children. Studies have shown that this relationship differs depending on maternal history of the disease. We employed the rigour of propensity score methods to assess this relationship using data from a birth cohort. METHODS: Using n = 662 children from the Wayne County Health, Environment, Allergy and Asthma Longitudinal Study, we assessed the relationship between early-life ETS and subsequent allergic sensitization via a positive skin prick test (SPT+) or at least one specific immunoglobulin E (IgE) ≥ 0.35 (sIgE+) in children aged 2-3 years. Propensity score estimation followed by full and nearest neighbour matching was compared with standard multivariable regression models. RESULTS: Among children without a maternal history of allergic disease, ETS was positively associated with allergic sensitization in children with an adjusted odds ratio (aOR) for SPT+ of 2.32 (95% confidence interval (CI): 1.28-4.22) and the aOR for sIgE+ was 2.53 (95% CI: 1.43-4.48). Contrarily, for children with a positive maternal history, the aOR for SPT+ and sIgE+ was 0.56 (95% CI: 0.24-1.32) and 0.43 (95% CI: 0.20-0.91), respectively. CONCLUSIONS: Using propensity score methods to rigorously control for confounding factors, ETS exposure was found to reduce the risk of allergic sensitization in children with a positive maternal history. There is a strong association between early-life ETS and the development of allergic sensitization for children aged 2-3 years without maternal history.

Early complementary feeding and risk of food sensitization in a birth cohort.

BACKGROUND: Exposure to solid food or cow's milk (complementary food) before age 4 months may confer immune protection (tolerance) or detriment (allergy). OBJECTIVE: We explored the relationship between introduction of complementary food <4 months and IgE to egg, milk, and peanut allergen at 2 years in the Wayne County Health, Environment, Allergy and Asthma Longitudinal Study birth cohort of Detroit, Mich. METHODS: At infant ages 1, 6, and 12 months, mothers were interviewed about feeding practices. Blood samples were collected at age 2 to 3 years to assess sensitization (IgE ≥ 0.35 IU/mL) to egg, milk, or peanut. RESULTS: For the 594 maternal-infant pairs analyzed, maternal mean age was 29.7 years, and 60.6% self-reported as African American or black. Infant exposure to complementary food <4 months was reported by 39.7% of mothers. IgE ≥0.35 IU/mL for egg, milk, or peanut allergen at age 2 years was observed in 23.9% (95% CI, 20.5% to 27.6%), 30.6% (26.9% to 34.5%), and 11.4% (8.9% to 14.3%) of children, respectively. The association between early feeding and sensitization was modified by parental history of asthma or allergy. In multivariable analysis, early feeding reduced the risk of peanut sensitization among children with a parental history (adjusted odds ratio, 0.2 [95% CI, 0.1-0.7]; P = .007). The relationship also became significant for egg when a cutoff for IgE of ≥0.70 IU/mL was used (adjusted odds ratio, 0.5 [95% CI, 0.3-0.9]; P = .022). CONCLUSION: In this cohort, complementary food introduced <4 months was associated with a reduced risk of peanut (and perhaps egg) sensitization by age 2 to 3 years, but only for children with a parental history of asthma or allergy.

Differences in total and allergen specific IgE during pregnancy compared with 1 month and 1 year post partum.

BACKGROUND: Pregnancy alters the function of many body systems, including the immune system. However, little is known regarding the effect of pregnancy on maternal IgE levels or atopy. OBJECTIVE: To determine whether pregnancy consistently influences serum levels of total or allergen specific IgE. METHODS: Blood samples were obtained from 764 women during the third trimester of pregnancy and 1 month post partum. A third sample was obtained from 106 of these women 1 year post partum. Samples were analyzed for total and specific IgE to 8 regionally common allergens using a commercially available system. Sensitization was defined as an allergen specific IgE level of 0.35 kU of allergen per liter or higher to any allergen. RESULTS: Total IgE increased significantly post partum, both at 1 month (40.36 vs 35.37 IU/mL intrapartum; P = .001) and at 1 year (44.97 vs 37.00 IU/mL intrapartum; P = .005). Allergen specific IgE decreased significantly at 1 month for cat, dog, ragweed, timothy grass, and egg (P = .001 to P = .02) but not for dust mite, cockroach, or Alternaria (P = .15 to P = .90). Similar patterns of change in total and specific IgE were seen at 1 year. However, on average, only 3.5% of participants changed sensitization status to the individual allergens studied during the 1 year of observation. CONCLUSIONS: Compared with intrapartum levels, total IgE levels increased significantly at 1 month and 1 year post partum. Conversely, at the same time points, IgE levels specific for common allergens significantly declined to most but not all allergens. Few women changed their sensitization status over 1 year.