To cite this article: Brunst KJ, Ryan PH, Lockey JE, Bernstein DI, McKay RT, Khurana Hershey GK, Villareal M, Biagini Myers JM, Levin L, Burkle J, Evans S, LeMasters GK. Unraveling the relationship between aeroallergen sensitization, gender, second-hand smoke exposure, and impaired lung function. Pediatric Allergy Immunology 2012: 23: 479–487.
Background: Contradictory findings on the differential effects of second-hand smoke (SHS) on lung function in girls and boys may result from masked relationships between host and environmental factors. Allergic sensitization may augment the relationship between SHS and decreased lung function, although its role in relation to the inconsistent gender differences in children has not been elucidated.
Hypothesis: We hypothesize that there will be differences between boys and girls related to early-life allergic sensitization and exposure to SHS on pulmonary function later in childhood.
Methods: Participants in this study (n = 486) were drawn from the Cincinnati Childhood Allergy and Air Pollution (CCAAPS) birth cohort study consisting of 46% girls. Allergic sensitization was assessed by skin prick test (SPT) to 15 aeroallergens at ages 2, 4, and 7, while pulmonary function and asthma diagnosis occurred at age 7. SHS exposure was measured by hair cotinine at ages 2 and/or 4. Gender differences of SHS exposure on pulmonary function among children with positive SPTs at ages 2, 4, and 7 as well as first- and higher-order interactions were examined by multiple linear regression. Interactions significant in the multivariate models were also examined via stratification. Comparisons within and between stratified groups were assessed by examining the slope of the parameter estimates/beta coefficients and associated p-values and confidence intervals.
Results: Increased cotinine levels were significantly associated with decreases in FEV1 (−0.03 l, p < 0.05), peak expiratory flow (−0.07 l/s, p < 0.05), and FEF 25–75% (−0.06 l/s, p < 0.01). The interaction between cotinine and sensitization at age 2 was borderline significant (p = 0.10) in the FEF25–75% model and showed an exposure response effect according to the number of positive SPTs at age 2; zero (−0.06 l/s, p < 0.01), one (−0.09 l/s, p < 0.05), or two or more positive SPTs (−0.30 l/s, p < 0.01). Despite increased polysensitization among boys, the association between cotinine and FEF25–75% among girls, with two or more positive SPTs at age 2, showed the greatest deficits in FEF25–75% (−0.34 l/s vs. −0.05 l/s and −0.06 l/s for non-sensitized girls and boys, respectively. Girls with two or more positive SPTs showed a twofold greater decrease in FEF25–5% (−0.34 l/s; 95% CI: −0.55, −0.13) compared to boys with the same degree of allergic sensitization (−0.18 l/s; 95% CI: −0.41, 0.06), although this difference was not statistically significant.
Conclusions: Reductions in lung function were observed among children exposed to SHS, and the number of aeroallergen-positive SPTs at age 2 modifies this relationship. Girls experiencing early childhood allergic sensitization and high SHS exposure are at greater risk of decreased lung function later in childhood compared to non-sensitized girls and boys and demonstrate greater deficits compared to boys with similar degrees of sensitization.