Association of prenatal maternal, prenatal secondhand, and postnatal secondhand smoking exposures with the incidence of asthma/atopic dermatitis in children: An epidemiological study using checkup data of mothers and children in Kobe city

Abstract

Objectives Despite suggested associations among smoking exposures and the prevalence of allergic diseases in children, studies examining the effect of prenatal maternal smoking and secondhand smoking on the occurrence of these diseases in children are limited. Our study aimed to investigate the association between prenatal maternal smoking as well as secondhand smoking and the incidence of asthma or atopic dermatitis in children.Methods We included checkup data of a total of 53,505 children living in Kobe, Japan, without missing values for exposure or outcome, between April 1, 2004, and March 31, 2013. The exposure variables were prenatal maternal smoking, prenatal secondhand smoking, and postnatal secondhand smoking till 4 months, which were assessed by maternal notification form and exclusively classified into eight categories. The outcome variables were the incidence of asthma or atopic dermatitis in the respective children up to 3 years of age assessed by a checkup questionnaire. The association between the smoking exposures and the development of asthma or atopic dermatitis up to 3 years was examined using a generalized linear mixed model with odds ratios and 95% confidence intervals (CI). Additionally, multiple imputation methods were used for the missing covariates.Results Of the 53,505 children, 27,210 (50.9%) were males and 26,218 (49.0%) were females. In total, 5,810 (10.9%) children were diagnosed with asthma and 4,964 (9.3%) with atopic dermatitis up to 3 years of their age. Compared to the children born to nonsmoking mothers during pregnancy and those without exposure to postnatal secondhand smoking, the adjusted odds ratio for the incidence of asthma up to 3 years of their age was found to be 2.04 (95% CI: 1.38-3.01) in children exposed to prenatal maternal smoking. Similarly, the adjusted odds ratio for the incidence of asthma in children exposed to maternal secondhand smoking during pregnancy was 1.12 (95% CI: 1.01-1.25) when compared with children who were never exposed to any smoking. Additionally, the adjusted odds ratio increased to 1.86 (95% CI: 1.42-2.44) in children exposed to both prenatal maternal smoking and secondhand smoking. In contrast, no statistical significance was observed among the smoking exposures and the incidence of atopic dermatitis in the children.Conclusions Our study confirmed that prenatal maternal and secondhand smoking were associated with the incidence of asthma in children. These findings suggest a need to focus on smoking cessation by pregnant women as well as by family members living together to prevent the development of asthma in children.