OBJECTIVEOver the past few decades, secondhand smoke exposure among children become more serious and with China's implementation of the national policy of family planning and the family structure change, domestic pet has gradually become popular. This survey aimed to investigate the interactive effects of pet ownership and environmental tobacco smoke (ETS) on children's respiratory diseases and symptoms.

METHODUsing a cluster random sampling method, 5 elementary schools and 10 kindergartens were randomly selected from each district of Shenyang, and all children from the selected schools were recruited in this survey. The information about the children's respiratory diseases, conditions of pets ownership and ETS exposure were collected by an international standard questionnaire from American Thoracic Society.

RESULTA total of 9679 questionnaires were distributed to all the students enrolled in the selected schools, and 8798 completed questionnaires were collected with a response rate of 90.9%. Finally, 8733 questionnaires were used for further analysis. The results showed that the number of the patients and the prevalence of persistent cough, persistent phlegm, doctor-diagnosed asthma, current asthma, wheeze, and allergic rhinitis in children were 835 (9.57%), 366 (4.42%), 559 (6.40%), 215 (2.46%), 229 (2.62%), 397 (4.55%), respectively. After controlling for the effects of age, gender and other confounding factors, the results from the multivariate unconditional logistic regression analysis showed that either pet ownership or the ETS exposure significantly increased the risk of prevalence of respiratory diseases and symptoms in children. Compared with control group children, only the prenatal exposure to passive smoking or domestic pets made the risk of children with allergic rhinitis increased respectively 34% (OR = 1.34, 95%CI = 0.99 - 1.80) and 106% (OR = 2.06, 95%CI = 1.28 - 3.31), while the exposure of these two factors made the risk of children with allergic rhinitis increased 376% (OR = 4.76, 95%CI = 2.65 - 8.85), compared with the separate effect, the range of increase was 2.5 times.There was a significant interaction between pet ownership and ETS exposure on persistent cough, persistent phlegm, and allergic rhinitis in children, whereas, the combined effects of these two factors on doctor-diagnosed asthma, current asthma, and wheeze was approximately as expected on the basis of their independent effects on an additive scale.

CONCLUSIONThis study provides evidence that pet ownership and ETS exposure increases the risk of respiratory diseases and symptoms in children, and there was a significant interaction effects between these two factors on some respiratory diseases and symptoms.