Pet ownership in utero and in childhood decreases the effects of environmental tobacco smoke exposure on hypertension in children: A large population based cohort study.

BACKGROUND: Little is known about whether exposure to pets influences the association between hypertension and environmental tobacco smoke (ETS). The current study aims to examine the interaction of pet ownership on ETS exposure and the development of hypertension in children. METHODS: From 2012 to 2013, a total of 9354 children, 5 to 17 years of age, were recruited from 62 schools in seven northeastern cities. BP in children was measured and hypertension was defined as an average diastolic blood pressure (DBP) or systolic blood pressure (SBP) at or above the 95th percentile for that child's age, sex, and height. Pet ownership in three different time periods (in utero, past 2 years, and currently) and ETS exposure data were collected from parents via a questionnaire. Two-level regressions were used for the data analyses. RESULTS: The data show consistent, significant interactions between exposure to pets and effects from ETS. Children who were not exposed to pets experienced stronger effects from ETS on hypertension when compared to those exposed to pets, and the protective effect of pet ownership became stronger with a greater number of pets in the home. Exposure to in utero ETS was associated with hypertension [adjusted odds ratio (aOR) = 1.32, 95% confidence interval (CI): 1.13-1.54] only for those children without pet exposure in utero but not for those with pets (aOR = 0.75; 95% CI: 0.49-1.15) (pinteraction < 0.05). Moreover, household dog ownership was related to significantly lower effects of current ETS on hypertension (aOR = 0.80, 95% CI: 0.61-1.05) compared with children without dogs (aOR = 1.26, 95% CI: 1.11-1.44) (pinteraction = 0.001). Interaction associations between ETS and pet ownership were more robust for girls than for boys and for younger than older children. CONCLUSION: This study indicates an inverse relationship between pet ownership and ETS, potentially pointing to pet ownership as protecting against the development of hypertension in children.