Environmental tobacco smoke exposure and chinese schoolchildren's respiratory health: A prospective cohort study

Background: Although China is the most coveted cigarette market worldwide, few studies have examined the longitudinal effects of environmental tobacco smoke (ETS) on health.

Purpose: To examine the relationship between exposure to ETS and respiratory health in Chinese schoolchildren.

Methods: The study subjects included 1718 children, who were never-smokers, aged 10.05±0.86 years and asthma-free at baseline. The children performed spirometric tests in 2006 and 18 months later. Parents reported the children's respiratory symptoms and illnesses, ETS exposure, and other related information by self-administered survey at both assessment points. The data were analyzed in 2010.

Results: Significant exposureresponse relationships were found between ETS exposure and coughing at night (p for trend<0.001); sneezing (p for trend=0.031); and sneezing with itchy, watery eyes (p for trend=0.006) in the first survey, and coughing at night (p for trend=0.019); phlegm without a cold (p for trend<0.001); and sneezing (p for trend=0.036) in the second survey. Compared with those who reported no ETS exposure in either survey, children who had a high ETS exposure level (>5 cigarettes/day) in either survey had lower growth rates in forced expiratory flow between 25% and 75% of forced vital capacity (FEF ₂₅₇₅; β= -0.104, p=0.020) and forced expiratory flow at 25% of forced vital capacity (FEF ₂₅; β= -0.077, p=0.027). A monotonic exposureresponse effect was observed between ETS exposure and the deficits in the growth rate of FEF ₂₅ and FEF _2575. 

Conclusions: Exposure to ETS increased the risks of respiratory symptoms in Chinese school-aged children and was associated with impaired lung function growth. A doseresponse relationship was observed for the latter effect.