In 2015, the average age of children with asthma covered by China’s medical insurance was 5.50 years old. This is in line with the widely accepted view that the onset of asthma in children is mostly within the age of 6 years old . Males accounted for 63.82% and females 36.18%, with a male to female ratio of 1.76:1. Some previous reports have been based on school or community epidemiological studies [18, 19], while our study was based on medical insurance data. There’s no difference in the estimate of asthma incidence between different ages and different genders, and these results are consistent with the global epidemiological trend in asthma . Studies on the natural process of asthma show that males have a higher risk of asthma than females in childhood . Before puberty (15 years old), males have an increased risk of asthma . However, it is a natural trend that the prevalence of asthma increases in females during puberty and adulthood . Due to the complexity of the causes of asthma, the relationship between the increase of asthma incidence with age and gender difference is not clear at present. It is generally believed to be related to the differences in hormones and genetic susceptibility between males and females .
Gilchrist et al. reported that the direct medical expenditure was estimated to be $1.01 billion ($1.04 billion in 2015), with a total of $401($413.96 in 2015) for each child with asthma, while the indirect costs were estimated to be $983.8 million ($1015.61 in 2015), which was $390 ($402.61) per child with asthma in 2012 . In Australia, the average annual cost varies from $85 to $884, depending on the severity of asthma, accounting from 0.27 to 2.86% of the country’s per capita GDP ($30,941). In 2015, the per capita direct medical cost of children with asthma in China was about RMB 525 (US$75), accounting for 1.06% of China’s per capita GDP, RMB 49,351(US $7020). Compared with these countries, the economic burden of children with asthma in China is relatively lower in the world. The average reimbursement rate of China’s medical insurance is as high as 67%, which in younger age groups is higher.
The cost of medication is the major component of direct medical cost, accounting for 72% of the asthma-related cost. This result is lower than those reported in Denmark (78%), Netherlands (87%), Spain (88%), and Finland (89%) [25,26,27,28]. As a result, compared with European countries, the percentage of the cost of medication in China is at a relatively lower level. Among the cost of medication caused by asthma, the cost of medications to treat asthma accounted for the highest percentage (25.82%), which was in line with the actual expectation. The cost of antibiotics was second only to the cost of asthma medication, accounting for 10.54%. Our analysis of year-round antibiotics use across different age groups, regions, and cities of different grades found that the overall use percentage of antibiotics was 50.26%, and the use percentage of antibiotics in children lower than 3 years old, Central China, and fourth-tier and below cities was the highest, reaching 63.64, 100, and 77.14%, respectively.
Paul et al.  reported that nearly 16% of children with asthma in the United States use antibiotics in outpatient visits every year. Knapp et al.  reported that 29% of US children visiting the emergency department for moderate and severe asthma were prescribed antibiotics. Although the overall antibiotics use percentage (50.26%) in this study is lower than that reported in the third epidemiological survey of urban children’s asthma in China (75.1%) , it is still high when compared with other countries, especially in infants and young children (63.64%), Central China (100%), and the cities of fourth-tier and below (77.14%). This indicates a certainly high degree of improper use of antibiotics in China. The possible reasons are as follows: During the acute attack of asthma, some children are misdiagnosed as having a respiratory infectious disease (such as pneumonia and bronchitis) and given inappropriate anti-infection treatment. Some doctors also prescribe antibiotics without analyzing blood tests or X-ray results. Murk  and Sun et al.  reported that the use of antibiotics in the first year after birth might increase the risk of asthma in children. It has also been reported that frequent use of antibiotics in early childhood is associated with increased frequency of asthma and wheezing attacks in later life . Improper use of antibiotics not only increases the economic burden of patients, but also increases bacterial resistance. This can lead to the disruption of normal bacterial flora balance and the displacement and endogenous infection of double infection bacteria, as well as other adverse drug reactions caused by drug allergies (e.g., asthma attacks and liver and kidney function damage) causing serious consequences. Therefore, all practitioners need to strictly control the indication of antibiotics, improve the awareness of the harm caused by the improper use of antibiotics, and use antibiotics cautiously.
Our research showed that the cost of examination account for 25.09% of other costs, and the cost of examination in pre-school children is higher than that in children lowere than 3 years old and school-age children. Further analysis of the examination percentage in different age groups, different regions, and different city grades found that the percentage of hematologic test (30.42%) and chest X-ray in certain subgroups is relatively high, and the percentage of asthma-related test is generally lower, such as pulmonary function test (12.17%) and allergen detection (5.82%).
As an objective index to judge airway obstruction, pulmonary function test is helpful for the diagnosis of asthma, and it’s an important basis for the determination of asthma control level and the selection of a treatment plan , as well as an important monitoring index for children with asthma who may develop into adults with COPD in the future . Studies have found that the pulmonary function test (PFT) is feasible for at least 50% of children aged 3 years old, and most children aged 4 years and older . Therefore, regular assessment of pulmonary function can be used as a routine test to monitor children with asthma. Bisgaard et al. found that children with asthma at 7 years of age had pulmonary dysfunction and increased bronchial responsiveness in the neonatal period . Owens et al. found that early infant pulmonary function decline can predict the persistence of asthma attacks in adolescents, and the continuous decline of pulmonary function indicates abnormal intrauterine pulmonary development or abnormal early infant pulmonary growth . This indicates that early monitoring of pulmonary function and timely control measures can prevent the occurrence of later asthmatic diseases. However, studies have reported that only 20 to 40% of primary care providers conduct pulmonary function test with symptomatic asthma patients, while as many as 59% of pediatricians never conduct pulmonary function test . In our study, only 12.17% of children had done pulmonary function test. It is thus necessary to raise people’s awareness of pulmonary function monitoring nationwide to provide a basis for early identification and prevention of asthmatic diseases.
Asthma, as one of the most common chronic respiratory diseases in childhood, is not only associated with airway inflammation, but also with a considerable percentage of allergies. Butz et al.  reported that allergen exposure is associated with acute asthma attacks, and allergies caused by repeated allergen stimulation is also an important cause of repeated asthma attacks. A large percentage of childhood asthma develops in infants and young children. Inhalant allergens are the primary factors leading to the development of persistent asthma in children younger than 3 years old, followed by dietary allergens , showing that the allergy test status is an important link in the diagnosis and prevention of asthma in children. However, in our study, only 5.82% of children were tested for allergens overall. This might be related to the high cost of allergen detection and the fact that this technology has not been fully popularized in primary hospitals, especially in the underdeveloped regions of mainland China.
X-rays are harmful to human health, especially for children. Although only 8.20% of the children in our study have received chest X-ray test, the percentage of use in the central region is as high as 42.86, and 22.86% in fourth and fifth-tier cities. Also, the younger the group age, the higher the use rate of chest X-ray. Minimizing the use rate of X-rays is not only beneficial to the life and the health of mankind but also can largely reduce the patients’ medical costs. Therefore, the use rate of a chest X-ray should be further reduced, thereby reducing unnecessary economic and health loss, especially for the younger age groups, the central region, as well as fourth and fifth-tier cities.
In our study, 98.58% of children with asthma were admitted to outpatient services, while the overall hospitalization rate was less than 2%. Among the total hospitalization cost of children aged 0–4 years, 5–11 years, and 12–17 years, children aged 0–4 years give the largest proportion, accounting for almost half of the annual cost . Therefore, the hospitalization cost of children in younger age groups is also a major factor in the cost of asthma. This might be related to the rapid change and severity of infants’ acute illnesses . In the use of all-cause medical treatment, the average hospital day of children with asthma in children lower than 3 years old was nearly 1.74 days. This result is lower than that reported in the United States  in 2009, in which the hospital day of children with asthma was 1.9, and the hospital day was gradually reduced during the study period (2.0 days in 2000), which might be attributed to the positive promotion of the Global Initiative for Asthma (GINA) program and the standardized management and guidance of Chinese guidelines for the prevention and treatment of childhood asthma in China [45, 46].
In our study, 62.08% of children with asthma were admitted to tertiary hospitals. Studies have reported that from 2009 to 2014, the number of tertiary medical services in urban regions in China has increased rapidly, while the number of visits to primary medical care decreased from 62 to 58% . Overcrowding of tertiary hospitals and underuse of primary medical institutions coexist, which not only wastes resources and affects the overall benefit of the medical service system, but also drives up medical cost and aggravates both the burden of patients and the medical insurance fund. Hierarchical diagnosis and treatment systems may be the solutions to this problem; that is, patients choose primary hospitals first, where the doctors refer patients to a hospital of certain grades, maintaining contact between all hospital grades, and differentiate urgent and nonurgent treatment of patients. According to this model, the main task of tertiary hospitals is to provide diagnosis and treatment services for acute and severe diseases and complicated diseases . Therefore, the hierarchical diagnosis and treatment systems need to be further implemented and strengthened, thereby promoting the rational allocation of medical resources for childhood asthma in China.