Residential proximity to main roads and the severity of asthma in children

Abstract

Background: Data from many studies suggest that traffic exposure can influence asthma among children. Most of these studies were conducted in Europe and America. However, there is less information on the association between traffic exposure and asthmatic children in China. This study investigated whether asthma severity in children was related with living near to major road in Guangzhou, China. Methods: The study method was case-control study. In this study, cases were with diagnosed asthma by physician and they aged between 1 and 14 years old. Controls were children without asthma in the same age range. Traffic exposure was measured as the distance from the nearest major road to home and to school weighted by the proportion of time spent in each location. Result: The longer the time-weighted distance being near to major roads, the lower the risks were associated with asthmatic children (OR=0.693 [0.504-0.953]). The other risk factors of asthma includes male compared with female (OR=2.696, [1.271-5.721]), age (OR=1.224 [1.078-1.391]), secondhand smoke exposure at home (OR=2.074 [0.985-4.364]), breastfeeding duration<6 months (OR= 1.423 [0.681-2.974] but also presence of pet (OR=0.508 [0.162-1.588]) and mold at home (OR=0.326 [0.152-0.697]). We also found the distance of home and school near to major roads were associated with asthma only among boys(OR=0.598 [0.373-0.957])，but not among girls(OR=0.802 [0.504-1.278]). The second hand smoke exposure was associated with asthma in boys (OR=3.459 [1.274-9.391]), but not in girls (OR=1.041 [0.306-3.539]). The estimated risk factors were not associated with the level of asthma severity except the time-weighted distance. After adjusted with other risk factors, the time-weighted distance had negative trend with the level of asthma severity (p-value=0.030). The time-weighted distance had no association with lung function (p-vale=0.779). Conclusion: The results show that the time-weighted distance near to main roads is associated with the risk of having childhood asthma. And it may be harmful for the asthma children lung function. The sex and second hand smoke exposure are also risk factors of asthma.