Prevalence, risk factors, impact and management of pneumonia among preschool children in Chinese seven cities: a cross-sectional study with interrupted time series analysis
Authors: Shi Haonan , Wang Tingting , Zhao Zhuohui , Norback Dan , Wang Xiaowei , Li Yongsheng , Deng Qihong , Lu Chan , Zhang Xin , Zheng Xiaohong , Qian Hua , Zhang Ling , Yu Wei , Shi Yuqing , Chen Tianyi , Yu Huaijiang , Qi Huizhen , Yang Ye , Jiang Lan , Lin Yuting , Yao Jian , Lu Junwen , Yan Qi ,   for the China, Children, Homes, Health (CCHH) Study Group
Published: June 2023

Abstract
Background
Pneumonia is a common disease worldwide in preschool children. Despite its large population size, China has had no comprehensive study of the national prevalence, risk factors, and management of pneumonia among preschool children. We therefore investigated the prevalence of pneumonia among preschool children in Chinese seven representative cities, and explore the possible risk factors of pneumonia on children, with a view to calling the world's attention to childhood pneumonia to reduce the prevalence of childhood pneumonia.

Methods
Two group samples of 63,663 and 52,812 preschool children were recruited from 2011 and 2019 surveys, respectively. Which were derived from the cross-sectional China, Children, Homes, Health (CCHH) study using a multi-stage stratified sampling method. This survey was conducted in kindergartens in seven representative cities. Exclusion criteria were younger than 2 years old or older than 8 years old, non-permanent population, basic information such as gender, date of birth and breast feeding is incomplete. Pneumonia was determined on the basis of parents reported history of clearly diagnosed by the physician. All participants were assessed with a standard questionnaire. Risk factors for pneumonia, and association between pneumonia and other respiratory diseases were examined by multivariable-adjusted analyses done in all participants for whom data on the variables of interest were available. Disease management was evaluated by the parents’ reported history of physician diagnosis, longitudinal comparison of risk factors in 2011 and 2019.

Results
In 2011 and 2019, 31,277 (16,152 boys and 15,125 girls) and 32,016 (16,621 boys and 15,395 girls) preschool children aged at 2–8 of permanent population completed the questionnaire, respectively, and were thus included in the final analysis. The findings showed that the age-adjusted prevalence of pneumonia in children was 32.7% in 2011 and 26.4% in 2019. In 2011, girls (odds ratio [OR] 0.91, 95%CI [confidence interval]0.87–0.96; p = 0.0002), rural (0.85, 0.73–0.99; p = 0.0387), duration of breastfeeding ≥ 6 months(0.83, 0.79–0.88; p < 0.0001), birth weight (g) ≥ 4000 (0.88, 0.80–0.97; p = 0.0125), frequency of putting bedding to sunshine (Often) (0.82, 0.71–0.94; p = 0.0049), cooking fuel type (electricity) (0.87, 0.80–0.94; p = 0.0005), indoor use air-conditioning (0.85, 0.80–0.90; p < 0.0001) were associated with a reduced risk of childhood pneumonia. Age (4–6) (1.11, 1.03–1.20; p = 0.0052), parental smoking (one) (1.12, 1.07–1.18; p < 0.0001), used antibiotics (2.71, 2.52–2.90; p < 0.0001), history of parental allergy (one and two) (1.21, 1.12–1.32; p < 0.0001 and 1.33, 1.04–1.69; p = 0.0203), indoor dampness (1.24, 1.15–1.33; p < 0.0001), home interior decoration (1.11, 1.04–1.19; p = 0.0013), Wall painting materials (Paint) (1.16, 1.04–1.29; p = 0.0084), flooring materials (Laminate / Composite wood) (1.08, 1.02–1.16; p = 0.0126), indoor heating mode(Central heating)(1.18, 1.07–1.30, p = 0.0090), asthma (2.38, 2.17–2.61; p < 0.0001), allergic rhinitis (1.36, 1.25–1.47; p < 0.0001), wheezing (1.64, 1.55–1.74; p < 0.0001) were associated with an elevated risk of childhood pneumonia; pneumonia was associated with an elevated risk of childhood asthma (2.53, 2.31–2.78; p < 0.0001), allergic rhinitis (1.41, 1.29–1.53; p < 0.0001) and wheezing (1.64, 1.55–1.74; p < 0.0001). In 2019, girls (0.92, 0.87–0.97; p = 0.0019), duration of breastfeeding ≥ 6 months (0.92, 0.87–0.97; p = 0.0031), used antibiotics (0.22, 0.21–0.24; p < 0.0001), cooking fuel type (Other) (0.40, 0.23–0.63; p = 0.0003), indoor use air-conditioning (0.89, 0.83–0.95; p = 0.0009) were associated with a reduced risk of childhood pneumonia. Urbanisation (Suburb) (1.10, 1.02–1.18; p = 0.0093), premature birth (1.29, 1.08–1.55; p = 0.0051), birth weight (g) < 2500 (1.17, 1.02–1.35; p = 0.0284), parental smoking (1.30, 1.23–1.38; p < 0.0001), history of parental asthma (One) (1.23, 1.03–1.46; p = 0.0202), history of parental allergy (one and two) (1.20, 1.13–1.27; p < 0.0001 and 1.22, 1.08–1.37; p = 0.0014), cooking fuel type (Coal) (1.58, 1.02–2.52; p = 0.0356), indoor dampness (1.16, 1.08–1.24; p < 0.0001), asthma (1.88, 1.64–2.15; p < 0.0001), allergic rhinitis (1.57, 1.45–1.69; p < 0.0001), wheezing (2.43, 2.20–2.68; p < 0.0001) were associated with an elevated risk of childhood pneumonia; pneumonia was associated with an elevated risk of childhood asthma (1.96, 1.72–2.25; p < 0.0001), allergic rhinitis (1.60, 1.48–1.73; p < 0.0001) and wheezing (2.49, 2.25–2.75; p < 0.0001).

Conclusions
Pneumonia is prevalent among preschool children in China, and it affects other childhood respiratory diseases. Although the prevalence of pneumonia in Chinese children shows a decreasing trend in 2019 compared to 2011, a well-established management system is still needed to further reduce the prevalence of pneumonia and reduce the burden of disease in children.