Epidemiological characteristics and influencing factors of combination of obesity and asthma in elementary and middle school students in Shanghai

Background Studies have found an association between obesity and asthma, but the characteristics of health-related behaviors in obese students with asthma are poorly understood.

Objective This study is conducted to investigate the prevalence and influencing factors of comorbidity between obesity and asthma in elementary and middle school students in Shanghai and to provide evidence for the prevention and treatment of such disease in the students.

Methods Based on the Chinese National Common Diseases and Health Influencing Factors Monitoring Project conducted in Shanghai in 2016, a stratified cluster random sampling method was used to select 12 elementary schools and 12 middle schools in 3 urban and 3 suburban areas in Shanghai. A questionnaire survey was conducted to collect information on allergic diseases, obesity, and related influencing factors of 5 911 students. Proportion was used to describe the distribution of selected demographic characteristics of the subjects. Chi-square test was used to compare the differences in demographic characteristics and lifestyles of the control group, the obesity group, the asthma group, and the obesity with asthma group. Multinomial logistic regression was used to analyze the influencing factors of obesity combined with asthma.

Results The prevalence rates of obesity and asthma were 13.2% (779/5 911) and 8.8% (519/5 911), respectively. The boys (17.9%, 10.3%) showed higher prevalence rates of obesity and asthma than the girls (8.3%, 7.2%) (P < 0.05). The prevalence of obesity with asthma was 1.4%, significantly higher in the boys (2.1%) than in the girls (0.8%) (χ²=18.42, P < 0.001), and higher in the urban areas (1.9%) than in the suburban areas (1.0%) (χ²=8.40, P < 0.01). The multinomial logistic regression analysis results showed that gender, residence, family history of asthma, and secondhand smoke exposure were associated with the risk of obesity combined with asthma (P < 0.05); namely, girls and living in suburban areas reduced the risk of reporting obesity with asthma, with OR (95% CI) of 0.307 (0.188-0.506) and 0.520 (0.324-0.834), respectively, and having a family history of asthma and being exposed to secondhand smoke increased the risk of obesity with asthma, with OR(95% CI) of 2.916(1.810-4.699) and 2.122(1.237-3.640), respectively. In addition, being exposed to secondhand smoke exposure and sweet food intake increased the risk of obesity, with OR (95% CI) of 1.473 (1.178-1.841) and 1.542 (1.411-1.713), respectively.

Conclusion High obesity rate and asthma rate of elementary and middle school students are found in Shanghai. Besides gender, residence, and family history, secondhand smoke exposure is also a potential factor affecting obesity combined with asthma. In this study, there is no significant difference in exercise and diet between students of obesity with asthma and those without the comorbid condition.