Changes in children’s asthma prevalence over two decades in Lanzhou: effects of socioeconomic, parental and household factors

BACKGROUND: The prevalence of childhood asthma may have changed with rapid economic development. This study aims to ascertain potential changes in asthma prevalence in relation to changes in socioeconomic, parental and household factors, based on a comparison between two periods spanning over 20 years in Lanzhou, a large northwestern city of China. METHODS: Cross-sectional studies using the same protocols were performed in Lanzhou, China in 1994–1995 (Period I) and in 2017 (Period II). Children of 6–12 years old from elementary schools were selected by a multistage sampling method. Information on the presence of asthma and asthma-related symptoms of children, socioeconomic status, feeding methods, parental illness and behavior patterns, as well as household characteristics, were collected through a questionnaire survey. Logistic regression models were used to estimate odds ratios of asthma prevalence with regard to socioeconomic, parental and household factors, respectively. RESULTS: Significant prevalence reductions were observed for paternal smoking, household coal use, and parental asthma, while the prevalence increased significantly for children sleeping in their own rooms or own beds, ventilation use during cooking, and parental occupation and education level after 22 years. In children, the prevalence of ever-diagnosed asthma decreased from 3.2% in period I to 1.5% in Period II (P<0.001); the prevalence of wheeze also decreased from 15.4% to 9.3% (P<0.001). Passive smoking (OR =1.531, 95% CI: 1.032–2.270) and poor household ventilation (OR =1.709, 95% CI: 1.208–2.416) were significantly associated with an increased prevalence of wheeze in Period I, whereas household mold (OR =2.112, 95% CI: 1.203–3.811) was significantly associated with prevalence of wheeze. Parental asthma history was associated with increased prevalence of asthma and asthma-related symptoms. Breastfeeding was significantly associated with reduced risk of asthma in period II children. CONCLUSIONS: The prevalence of asthma and that of asthma-related symptoms were lower in 2017 than in 1994–1995 in school children living in Lanzhou. In 2017 with increased urbanization and industrialization, breastfeeding became a significant protective factor and household mold was a significant risk factor for asthma diagnosis and asthma-related symptoms. Promoting breastfeeding and household mold control is recommended to reduce the risk of childhood asthma in contemporary Lanzhou.