Obesity enhanced respiratory health effects of ambient air pollution in Chinese children: the Seven Northeastern Cities study.

OBJECTIVE: Experimental data suggest that obesity enhances the effects of ambient air pollutants on exacerbation of asthma; however, there is little supporting epidemiological evidence. The aim of present study is to evaluate whether obesity modifies the association between ambient air pollution and respiratory symptoms and asthma in children.
METHODS: In Northeast China, 30 056 children aged 2-14 years were selected from 25 districts of seven cities. Parents of the children completed questionnaires that characterized the children's histories of respiratory symptoms and illness, and associated risk factors. Overweight and obesity were calculated with an age and sex-specific body mass index (BMI, kg m(-2)), with BMIs of greater than the 85th and 95th percentiles defining overweight and obesity, respectively. Average annual ambient exposure to particulate matter with an aerodynamic diameter 10 μm (PM(10)), sulfur dioxide (SO(2)), nitrogen dioxides (NO(2)) and ozone (O(3)) was estimated from data collected at monitoring stations in each of the 25 study districts.
RESULTS: We observed consistent and significant interactions between exposure and obesity on respiratory symptoms and asthma. The associations between each pollutant's yearly concentrations and respiratory symptoms and asthma were consistently larger for overweight/obese children than for normal-weight children, with odds ratios (ORs) ranging from 1.17 per 31 μg m(-3) for PM(10) on wheeze (95% confidence interval (CI): 1.01, 1.36) to 1.50 per 10 μg m(-3) for NO(2) on phlegm (95% CI: 1.21, 1.87) and cough (95% CI: 1.24, 1.81).
CONCLUSION: These results showed that overweight/obesity enhanced respiratory health effects of air pollution in the study children.